Solnhofen '" A study in Mesozoic palaeontology "
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K. W. Barthel N.H.M. Swinburne S. Conway Morris
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Solnhofen A study in Mesozoic palaeontology
K. W. Barthel Form erly of InstilUle for Geology alld Pa/aeom %gy Technical University , Berlin
N. H. M. Swinburne Departmem of Earth Sciences The Open Uni versity , Millon Keynes
S. Conway Morris Department of Earth Sciences University of Cambridge
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CAMBRIDGE
~ UN IYE R S ITY I) H ESS
Published by the Press Syndicate of Ihe University of Cambridge The Pitt Building. Trumpington Street. Cambridge CB2 l RP 40 West 20Ih Streel. New York, NY 10011-4211. USA JO Stamford ROlId, Oakleigh, Melbou rne 3166. Australia Originally published in German as So/nhoJm: Ein BUck in dit Ergrschichft by Ott Verlagl, Thun, 1978 and 0 Ott Verlag Thun 1978 This revised translation first published in English by Cambridge Universit y Press 1990 First paperback edition (wit h corm:tions) 1994 English translation 0 Cambridge University Press 1990 Printed m Great Britain at the University Press. Cambridge I1mis" Librur), ralilloRuillS ill publicu/ioll du/o
SMthe!. K. W. (K. Werner) 11./978 Solnhofen. - Rev. cd. I . West Ge rm any. Jurassic Strata . Fossils I. Ti tle 11 . SWinburne. N. H. M . (Nicola H. M .) Il l. Co nway Morris. S. 560' . 1'7640943 Librory of CongrtsJ cora/oguillg in publicOliOlI dOlO
Barthel. K. Werne r. !Solnhofc n. English] Solnhofen: a stud y in MeSOl:oie pa!ocon tology/K. W. 8arthel; [translated and revi$Cd by] N. H. M. Swinburne: [edited by] S. Conway Morris. p. em. Translation of: Solnhofen . Includes bibliographical references. ISBN 052 1 33344 X I. Palaeontology-Ju rassic. 2. Pal;leo1l1ology-Germany (West)Solnhofen. I. Swinburne. N. H. M. (Nicola Helga Marga ret). 1962. [I. Conway Morris, S. (Simon) Ill. Tille. 0E.733. 83713 1990 560' . I'7640943-dc20 1'9·25440 CIP
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Contents
I', d"cc hhrcv iations for museums
Tht Soln hofen limestone Introduct ion: T he limestone from Solnhofen IlislOry of plattenkalk exploitation
Cullections of foss ils
a
vi i
ix
4
9
( ;t'ological history and stratigraphy G eological history of the Southe rn Fra nconian A lb Pulacogeography and fac ies dist ribution in Late J urassic li mes
17 17 24
IIi'lI'UJ,:nl,)hy of the Solnhofen Plattenkalk
38 38
t ,'hv logy inlhe Solnhofen-Eichstatt a rea ()ccurrcnce of macrofossils ( ;l'l1 in ~ and microfossi ls llill,!!c nc tic altera tion of the sediment Ih'd' slrihut ion of e lements
1',lllu'ocnvironmcn( a nd sedimenta tion I'u lucucnvironmenl 111\' I'c~ tri c l ed basin model r h ~' mi " lr y or the Solnhofen waters and special preservation IIloml1" of microorgan isms I h\' i:ya no hactc rial mal t\ ilc pu:o.lliona l illodc l (Itill" (\e pi)',ilion,l1lhco ries
1'"lnl'\H'voluIo;Y 1' ,.I ,ll'udlllUtlc 1 II! III 1he lago o n 1(\'1' 111 1 ~'il1l11nIlI111i c~ 11'11 v"11 i" j CC()"Y' iC!11 '
40 41
49 52 56 56 56
59 64 64 65
67 71 71
73 79
84 v
Colltellts
6 Taphonomy Introduction Biostratinomy of the marine biota Biostratinomy of the terrestrial biota Fossi l diagenesis Chemistry of fossil preservation 7
The Fossils Int roduction Monerans and prot ists ~_
Non-vascular plants - brown algae Vascular plants Gymnosperms - seed ferns, Bennettitales. ginkgos , conifers Animals Invertebrates Sponges Cnidarians - jellyfish , hydrozoans , corals Annelid worms Bryozoans Brachiopods Molluscs - bivalves, gastropods, cephalopods Arthropods - crustaceans, chelicerales, insects Echinoderms - sea-lilies, starfish , brittle stars, sea-urch ins, sea-cucumbers Vertebrates Fish Reptiles Birds
89 89 89 93 96
100 102 102 102
lID
103 103
103 112 11 2 112 112 117 117 118
119 129 153 160 160 173 191
8 Conclusions: The Solnhofen Plattenkalk and comparisons to other plattenkalk lagerstattcn Summary of the characteristics of the Solnhofen Plattenkalk Olher plattenkalks wil h exceptionally preserved fossils
202 202 203
Appendix: Faunal and ftora ll ist Bibliography Systematic index Gener;!1 index
206 217 231 234
Preface
S ~'lhtll e n t ary rocks usually teem with fossils, but palaeontologists have long Il'I.'ognized that as a sa mple of o riginal life they are grossly in adeq uate . Th is is Im ply because in most circumstances only the resistant she lls and bones can IIIV IVt.! \0 fossilize. Very occasionall y, howeve r, the curtain of preservatio n is illt l' d slightly highe r and we begin to o btain a glimpse into the extraordinary '''Ilure of former life. Such deposits , where delicate and soft-bodied creatures m ' fossilized , are gene rally known as fossil1agershitten. Of these the Solnho10"11 IlIllcstonc is the most renowned Jurassic example. Over the centuries this '("1)("11 has produced a diverse collection of supe rbly preserved fossils, includ* 111 ", !lome anim als showing soft -part preservation . The Solnhofen organi sms are thl1l1t1oht to have been washed in to hypersali ne lagoona l basins and buried t 'l li dl y by fin e micritic mud , by which means they have been exceptio na lly
l't ~·'lC rved.
I ht ~ book com mences with a short history of the scient ifi c and commercial , _plll rlltion and explo.itation o f the limestone. The fo llowing chapter then p uts (ill' Solnhofen limestone into the context o f south G erm an stratigraphy and v. Illogical history . It next focllses upon events in La te J urassic times and the o",l uho fcn area. T he third cha pter presents a precise petrological description of Ih, Solnhofen limestone fro m its appearance at outcrop to elect ron microII l ullh~ of the microfa cies. Lit hological detai ls and geochem ical information are II • It 10 reco nstruct the palaeoenvironment at the site of depositio n, and , uIIl! lIl ll11S necessary fo r special preservation . The remai ning sections o f t he [< • •ilk pe rtain to the foss ils themselves: the o riginal palaeoecology o f t he ' " 1(11 111" 111 5, the short bursts (or last gasps) of life in the lagoonal basins and t he 1,11'hullomic processes affecting the fossils from buri al unti l their final exhumaI (un In the Im;1 chapler Ihe fossils are presented taxono mically , accompanied 11\ II "Inking co llection o f plates . Willi.. , preserving Ihe spirit of Barthel's book , this version is intended fo r a . 11. , . ~' udvanccd readershi p . I, is considerably reordered and more than half is 'I' w t1I (tic rial. Th is accommodates a change in emphasis towards discussio n of III! Solnhofen pa laeoe nvironment and the condit ions required for special I'" ~I'rv llti {) n . Th us it incl udes import ant research material not previously jtl'llllIhlc in an ea ~ jl y OI(;ccss iblc for m . In particular, emphasis is given to l it hll llt Kcupp's dCll1i led dcscription of the microfacies and discovery of
vii
Prcf(/c~
pu t.Hive cyanobacterial spheres. togethe r with his resultant stromatolite depositional theory. Meyer & Schmidt- Kaler's excellent book concern ing the stratigraphy lind palaeobiogeography of the area. published in 1984, has also been an im porta nt source o f material. K. Werner Barthe l slldly died in 1978, the yea r afler publ ication of his book Solllllofell : £ill Blick i1l (lie £r
1
The Solnhofen limestone
Introduction: The limestone from Solnhofen IIH' region known as the Southern Franconian Alb (Sudl ichc Friinkische Alb) Ih'\ lu\IIO the north ofthe city of Munich in sout hern Germany (fig. 1. 1). It is a III)!iI plateau land whose gently sloping hillsides arc cui by a few prominent '!llll'),' '"eh as the Danube and the Altmlihl. The rivers cut down through ma ny 11111l1In:d, of metres of Jurassic limestones, and one oflhese unils of limestone,
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II, I I ('l'ogruphy of ~o uthcrn Germany. Thc boxed area within thc Southern • 'n" ~"tlhlt1 1\1\1 .. luIW \ the I(lCUtlOli of li~. 1,2.
Th e Solnhofen limestone
that named after the small village of Solnhofen, is known throughllut the world for the astonishing richness of its fossils. To palaeontologists of this century, the Solnhofen lirncslOlle 1~ a llIuch acclaimed fossillagerstiitt e, a fossil deposit rich in infonll;Hion ahOlIl life at a certain time (very latest Jurassic) in the earth's past. The quanlll y of information is large because of the exceptional quality of the speci ll1 en~, it self a consequence of unique depositional conditions. During de position , organisms which ca me to be buried in the Solnhofen mud were likely to be preserved intact, and the Solnhofen fossils are usually complete skeletons, freque ntl y surrou nded by an imprint of the original soft tissue. Individually, specimens can present so much detailed information , that the precise relationship of the fossil o rganism to present-day form s can be established. In the ric h assembl
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Fig. 1.2 Locality map showing position of the plattenkalk basins amongstlhe spongealgal mounds. Updated after Meyer in Meyer & Schmidt-Kaler (1984).
The Solnhofen limestone
biohe rmal limestones (see fi g. 1.2. distribution o f pla tte nkalk basins). The biohe rms, mounds o f carbonate sedime nt tra pped by growi ng o rga nisms, projected from the seafl oor whilst pla tte nkalk was de posited in the basins. In each of the basins plattenkalk o nly form s a part of the total seque nce, although most quarries ex ploit th is litho logy. Qua rries a re concen trated in the weste rn pa rt of the area because he re the plattenkalk is of the most pure a nd fi negrained qua lity. Of these platte nkalks by far the most importa nt is the Solnhofe n Platte nk alk. This lithostratigraphic unit varies across the regio n a nd rocks from diffe re nt quarries serve slightly diffe re nt marke ts. Q ua rries to the north o f the small town of Eichstiitt produce sheets of 1-2 COl thick ness wh ich serve as fl oor a nd wall ti les, whereas to the east o f Eichsta tt much th icker slabs are found . Lit hographic print ing stones come fro m the a rea a round Solnhofe n, whe re their homogeneous. fi ne·grained texture a nd slight porosity make the m ideal fo r this purpose. From the easte rn quarries o f the Painte n area the rock is broke n up to make lime .
History of plattenkalk exploitation Cent uries of hum an culture in the Southe rn Fra nconia n A lb a re e xpressed in plattenka lk . In the caves of the late Stone Age , platte nkalk was used fo r scratched drawings and coloured murals. T he fl at , regula r stones of pla tte nk alk m .. ke it ideal as a building material. In Roma n times platte nkalk was used in the construction of fronti e r forts along a defe nsive wall which stre tched across the plattenka lk a rea a nd ke pt o ut the northe rn Germa nic tribes. The Roma ns also used the stone as a facing stone , for example in the li ning of baths (fig. 1.3) , and platte nkalk tablets were also used fo r inscri pt ions. In the Middle Ages the stone conti nued to be used in the constructio n o f houses and ot her buildings, especially for floor (fig. 1.4) a nd fo r roof covering. It was also a valuable export. In the church of Hagia Sofia in Ista nbul can be found a medieval mosaic fl oor made from platte nkalk ti les, which , accordin g to a th irteenth ·ce ntury chronogra phe r were shipped from the town of Kelheim in the Southe rn Franco nian Alb. The a rchitectural flourish which acco mpan ied the Re naissance e ra o f the sixteenth and seventeen th centuries profited from the use of planenkalk . Ma nsions and co ttages ali ke were paved with the highly prized sto ne. Sculptors scraped and chiselled the fin e·grained mate rial into gravestones and me morial plaques (fig. 1.5) , some of which a re still visible in local churches today . A no the r method of producing a relief e mployed by a rt ists of th is period involved the e tching of uncovered portions o f the stone with a weak acid . It was Alois SCll cfc tde r in 1793 who was the fi rst to c xploill his prope rl y a nd it led him to the ' discove ry' of lithography. The lege nd of th is invell tion run .. ;. .. fo llo ws: Se nefelde r wished 10 ma ke .. li)'1o f a numberof itCI1\), whil:h he wo nt ed a wa),he r
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The SOfllhofell limcslOlle
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finely polished and the pllinted on to the using a fatty Before printing thc block is wetted with water which is llbsorbcd by the I arcas of the stone. When the block is inked in thc printing process, o nly those parts which were covered with the lithographic ink will take up the printer's ink, whilst the ot her parts of the block will repel il. Pl:ltes each around 300 x 250 mOl ; in the Museum of Solnhofen Aklienvereins, Maxberg bei Solnhofen.
plallenkalk over their heads. More suitable for steeper roofs , is the lIlternativc mcthod whereby ti les with a shaped , semicircular end are laid to form a pallern rescmbling a beaver's tail (fig. 1.9). Today , modern synthetic tiles are uscd to an increasing extent and the o ld tradition is disappcaring. Plattenka lk is still quarried by the same methods that have been used for centuries. T he work in extracting and prcparing the slabs is almost entirely manual , the only piece of machinery adopted being a digger used to clear away surface debris. From then on everything is done by hand. A sledge-hammer is used to free suitable blocks (fig. 1.10), and a li ghter hammer to begi n shaping the stones, and in the workshop on site a trimmi ng hammer and a specialized pair of tongs are used to perfect the shape (fi g. 1.11). Onl y about a quarter of the matcrial issuitablc as a building stone and of this the poorer quality , but still frost-resistant, sla bs arc left unshaped for garden paths lind terraces. A very small percentage of stones is su itable as lithographic printing slone,. These stones ;;Ire h;lI1dlcd with care und fin ely polished .
Collections of fossils
Fig. 1.7 Drawing of SCllcfcldcr·s original lithographic prcss.
Fig. 1.8 A traditional mcthod of ti ling thin, unshaped plattcn kalk tilcs (I..nown as a 'Legschiefer' roof) . This mo.::t hud is suitable only for covering fl at wllf).. u~ing
Collections of fossils Ma n discove red fossils in the Solnhofen rocks long ago. In the late Stone Age they arc known to have been gua rded as ornaments or pe rhaps used as amu lets Ih:~ i ~n:ttcd with magical properties. Fossils have always been much prized by the l oca l ~ for their beauty. Naturally most foss ils were fo und by the men who !Illumed the stone as a building material. At first quarry owne rs allowed the tIIl'lI to kcep the fossils and so quarrymen buill collect ions. As the fossi ls hn;:ulIlc well known , so quite It trade developed with buyers from both home .IHllllbnmd. Th e inllati on in pricc was not ed as early li S 1781 by J . B. Fischer, who rC(lllrl cd : ' In rcec nt time!. tile price o f Ihc'>e nlritics ha" SO'lred and it is not o
Th~
Solllirofell
limaroll~
Fig. 1.4 Mosaic floor made or plattenkalk , in the Abbey or Ottobcuron, Bavaria , exemplifyi ng the subtle variations of shade in this decorative stone . Photo by Rolf Wihr, Bamberg.
woman to collect. As he had no paper to hand , he began to write on a slab of limestone and used a rather greasy ink . T o make the message more prominent he washed the slab with a weak acid which was only absorbed by those parts of the limestone not covered with the ink . This had the effect of dissolving away the surrou nding limestone and enhanci ng the letters from the background . When a sheet of paper was placed o n the stone he produced an exact mirrorim age print of the inked design on the stone. Senefeld er immediately recognized the possibilities and spent some lime perfecting the art. The precise replication ofa drawing by this method has e nsured its popul arity with artists o f many generations. Some of the most me morable examples of this art come in the grand lithographic plates of Henri Tou louse- Lautrec, the sharp images with which Honore Daum ier portrayed the wellknesses of his fellow men. and the drawings by wh ich KiHhe Kollwitz emphasized human suffering. Some examples of lithogruphic pl ates together with a lithographic printing press are presented in fi gs. 1.6 & 1.7. The heyday o f lithography was to last OJ mere hundred ycar~ . uft er which it was surpa<;sed by newer and chcuper processes . Today few Il thuwnphlc "Iunc",
History of plattenkalk exploitation.
l ig. 1. 5 Bas-relief in Solnhofen stone entitled The judgement of Paris' by Doman I kning. copied from an original woodcut by Lucas Cranach in 1508. Now in the \lul pturc section of the State Museum in Berlin. Size 220 x 197 mm.
ure required and plattenka lk is mainly quarried for use as a build ing materi al, hoth for local needs and fo r export. Shaped and polished ti les make fin e floor un d ~tairc a se coveri ngs and wi ndow su rrou nds. Roofs of Solnhofen slate give the local houses a di stinct ch
The Solnhofen limestone
Fig. 1.9 Roof made of shaped tiles of Solnhofen Plattenkalk (known as a 'Zwickwschen' roof). This is typical of older buildings of the Altmuhl area. Photo by N. H. M. Swinburne.
unusual to find that a fine, well preserved piece with both the concave and convex sides would fetch o ne, two or perhaps even four ducats' (from Schwertschlager in 1919). One of the first major scientific concerns with the Solnhofen fossils is demonstra ted in the description published in Lat in by J. J. Baier in 1708. The full title of th is work is Oryktographia Narica sive rerum /OSSilillffl et lid minerale regflum pertillentilllPl in lerrilorio Norimbergetlsi ejllsqlle viC;II;a observatarum sllccillCta descriptio, in effect, 'A description of fossils from the Nuremberg region'. With the resurgence of interest in the natura l sciences at the beginning of the nineteenth century and the increased popularity of palaeontology came the first systematic collections and detailed publications. Amongst the first important monographs about the Solnhofen flora and fauna are those of E. F. Germar, A. Hagen, G raf Georg zu Munster, A lbert Oppel. Baron Friedrich von Schlotheim and Andreas Wagner, whose names arc preserved for posterity in the fossils they described . The basis for much of the curren t knowledgeof reptiles stems from the numerous work., of Ilermann VOII Meyer, and this scienti st has also gone down in history as the author of the original description of ArclUleolJleryx. In 1860 an isolated fca thcrwa~ found in the So lnh tlf~' n rt)(;k .. (lilt 7.%) rhtll
Col/ee/ions of fossils
-A--;:.' ,....c/ IIg. 1.10 Splilting the plaltenkalk slabs. Piles of slabs break free from the rock along natural vertical joints and they are then splil along beddi ng planes, All work is manual tilklll& place outdoors in summertime, and under make-shift roofs in wintertime. Only about half the stone can be used and the rest is thrown on the spoil tips. unexpected discovery of bird remai ns in rocks which dated from the age of the lh nosaurs caused a sensa tion. (The find did not however extend the st ratiJ.(rll phic range of the birds; the tracks of some bi pedal dinosaurs, misinterpreted ,I' bird footprints, were already known from the Triassic.) A yea r afterwards thc !>kc lcton of a feathered creature was unearthed. When examined closely the , kcleton was clearly that of a reptile, but was surrounded by the unmistak.thlc Imprint of feat hers which impe lled its classification as a bird . The firsl Irduu!o/Heryx was obtai ned by a local doctor, Carl Hiibe rlei n , who collected hl'~ l l s. Haberle in actua lly received Archaeopteryx from o ne of his patients in Ilcu of medical expe nses. With the great importa nce attached to this specimen a pI icc of £700 , considered exorbitant at the time, was ex tracted from the British ~ ht 'ic um (a price which included a large number of other Solnhofen fossils) and Ihe flr,t Ardweopreryx ca me to reside in London. I he find could scarcely have been made al a more opportune time. Only IWO \"\"111"' clI l'lier Darwin had publi!>hcd his first edition of 0" rile Origin of Species .lIld Artlwl!ofJleryx (ancie nt wing) was hailed by some as Darwin's predicted 111"\1118 lillI. ' between the replllc ~ and the birds . It is su rprising that Darwin 's II
The Soillhofen IimeS/Olle
Fig. 1.11 Shaping and trimming in the workshop. In the workshop the slabs are trimmed with
strongest advocate, T. H . Huxley, did not , at first, see Archaeopteryx as a form tra nsit ional between the repti les and the birds but as a fully fl edged bird . Huxley had thought that the birds had evolved [rom small ru nn ing dinosaurs (a view wit h which we now agree) , although via flightless birds sim ilar to ostriches, and as long ago as the Palaeozoic. Hux ley used the sma ll Solnhofen di nosaur Compsogllatlllls (which was known from the one specimen described by Wagner in 1861) as an example of a bird-like repti le and later remarked on its similarity to Archaeopteryx, the reptile-li ke bird. Archaeopteryx was fo rmall y described by the British palaeontologisl Richa rd Owen who, although he believed evolut ion had taken placc , was vigorouslyopposcd to Darwin's theory of Na tural Selection. By profession a comparative anatomist, he believed that the va riety of life could be explained as predetermi ned mod ifications on a general plan and had constructed not ions of what he believed to be 'archaetypal vertebrate' . His interest in Archaeopteryx focu!>cd more On the supposed prescnce of cmbryon ic I.:haracteristics, such as the unfu ..ed vertebrae in the tai l. that revealed the nature of the archetype , 1\ It h(lu~h II I"(·III1t·oIJlfryx was, for him , cie(lrly a bird he did sec it a!> iI ' transitluIlU! h)"~I " 11lthnugh he
,Ill
Collections of fossils
thought that Archaeopteryx had evolved from the long-tai led pterosaur Rhamphorhynclllls (see Gou ld 1987). Nowadays we think that small running dinosaurs , relatives of CompsoglIathus, could have given rise to Archaeopteryx some time in the Late Jurassic. Both Archaeopteryx and Compsogllathus are described in chapter 7, where the rcader can see just how similar the creatu res are. The evolution of Archaeopleryx, the acquisition of feat hers and the origin of flight are subjects still bci ng actively debated. (The reader is referred to the symposium volume of the Archaeopteryx conference, held in Eichstatt, in 1984, edited by Hecht el al. 1985.) Recently , Archaeopteryx has again been in the public eye because of allegations by the physicist Fred Hoyle and mathematician C ha ndra Wickramasinghe (1986) that the fossils are the result of clever ni neteemh-century rorgeries. They claim that skeletons of the small dinosaur Compso811atlwswere take n, areas around the bones excavated and then infi lled by a paste made of ground-up limestone together with a bind ing agen t. The feathe rs of a modern bird were then pressed into the cement to make the impressions around the !>ke leton. Hoyle and Wick ramasinghe claim a major conspiracy involving Haberlei n , Owen (who alleged ly commissioned the forgery in order to undermine Darwin and Huxley) and a succession of curators at the Natural History Museum . Hoyle and Wickramasi nghe's allegations have been shown elsewhere (Charig et af. 1986, Swi nburne 1988, amongst others) to be mischievous and utterly without foundation. In 1877 a second Archaeopteryx was fou nd. It possessed even finer features as well as a complete skull and was sold to the museum of Berlin by Dr lliibcrlein's son, Ernst Haberlein . This Haberlein, together with a nother doctor, Dr Redenbacher [rom the local town of Pappe nheim, assembled a fi ne collection of Solnhofen fossi ls in the middle of the nineteenth century. Specimens in many museums sti ll bear the labels saying ' Haeber1ein'sche Samml ung' (from H abe rlein 's col lection) or ' Redenbachersche Sam mlung'. Archaeopteryx was but one of the splendid foss ils from the Solnhofen IOC;l lities and interest in the e ntire range o f fossi ls was stimulated . Major collections were established and Ihese encouraged a consideration of the So lnhofen fauna a nd flora as a whole. The first list of fossils was compiled by Ludwig Frischmann in 1853. In 1904 Johan nes Walt her published a comprehensive work e ntitled Die FalilUl tier SolnhoJeller Plattenkalke. This sum marlied Frischmann's list into a total of 650 known species, now thought to be an liver-estima te as it includes many incomplete a nd juvenile specimens as \cparate species. A more accurate figure is thought to be around 600 (0. Viohl , pen•. comm. 1986). Walther was also first to deal with the relat ionsh ip of the nrgilnisms to the sediment in which they were buried. In pa rticular he observed that almost all !>pecime ns were loc
13
Tile Solnhofen limes/om!
land to the south and wit h a barrier reef and the open ~a tn the north . Marine sediment was carried over a barrier reef into the lagoon where it settled , the water then drained back to the sea, through the reef. lellvi ng a sticky mud. The clayey in terbeds were dilutions of this marine lime mud by terrestrial dust. Today the main tenets of this theory still remain although the situation of land and sea is approximately reversed (see fig . 4.1, p. 57), and Ihere is no need to postulate a period of subaerial exposu re for the sediment (sec deposition, p. 56). In the present century we have come 10 know much more abou t carbonate sed imentology, but o ur knowledge of the fossils has, in some cases, scarce ly progressed. Some groups have not been reconsidered since their origi nal nineteenth-century descriptions although o ther foss ils, such as the rept iles and of course ArclweOI)/eryx, have received much greater attention. After the firs t two ske letons of Archaeopteryx were found in the late nineteenth centu ry it took another hundred years until four more were recovered. Archaeopteryx no. 3, of which on ly the torso is present, was found in 1956 at Langenaltheim , the sa me locality as the first bird , by a quarry worker in whose possession it still remllins. It was described in 1959 by Florian Heller. T he next two were, curiously enough , al ready lying in museums. The Archaeopteryx which came to light in 1970 had actu ally been dug up in 1855, some five years before the discovery of the fi rst feather. This bird had lain in a museum in Haarlcm in Holland under the title of the small fl yi ng reptile' Pterodllclyills crassipes', to which it is superficiall y similar. On closer exa mination the imprints of fe athers around the body were observed, me riting its reclassification as Archaeopteryx , and it has since been described by John Ostrom (1970). The fifth individual is the famous Eichstiitt specime n. It is complete, although about two-th irds the size o f the ot hers and differs in other important respects. Found in 1951, it was provisionally described o nly in 1973, but has subsequently been monographed by Peter Wellnhofer. It is on public display at the Jura-Museum in Eichstatt. Very recently, a further, sixth specimen has been recognized . Thi sspeci men, which was also collected several years ago, was found by a Turkish migrant who worked at one of the Solnho fen qu arries. He sold the fossil to one of the larger Solnhofen collections, that belonging to the community o f Solnhofen , the Burgermeister-Mul1er-Museum, where it is now on display. He claimed that the fossil came from the Solnhofen region, although it shou ld then have belonged to the quarry owners and he could not have rightfully sold it. However, the slab in which the fossi l lies is of the type much more typical of the EichsUitt area. Once in the museum it lay undisturbed until the curator, He rr Muller, came across it, cleaned and prepared it , and came to the conclusion that it was the small dinosaur Compsogl/(l/Iws. As this in itsclfwou ld have been quite noteworthy , Muller showed it to the cura tor of the Jura Mu\cum, Eichst:ill , Gunter Vioh!. Viohl noticed that the arms we re too Itll'~ cClIl1jl(lrcd with the length of the body fo r it to be COItlIJSOgllfltllll.f, 1l1li! , hut t h~'1 \. Vvl'IC Ihe
Collections of fossils
im pressions of feather veins under the left wing. The specimen is now accepted as the sixth exam ple of Archaeopteryx and (despite its dubious origin) is known as the Solnhofen specimen . Details o f this latest fin d. together with a ll other examples of Archaeopteryx are listed in Table 1. 1. Table I. I The Archaeopteryx specimens Year of find
Original locality
Description
I'cat her (part illld counterpart)
1860
Solnhofen
H. v. Meyer 1861
ht , or London 'l'lCrimen
186 1
Langenalthcim (Solnhofen)
2nd . or Berlin \IloCClmen
1877
Blumenberg. Eichstatt
Ii'll. or Maxbcrg
[956
Langcnalthei m (Solnhofen) Riedenburg
Name
~ 1'lC c llncn
·lI h, lIaarlem or 1855 I cylcr specimen 'Ih. or Eichstatt "1'lCClmcn
1951
Workerszell , Eichstiitt
"Ih. or Soln hoIl·n'l)cclIl1Cn
"'"'
Ekhst,itt
,I TC:L
Present ho using
(a) East Berlin , Museum fil r Naturkunde der HumboldtUniversitat (b) Munich , Baycrische Staatssammlung fiir Paliiontologie und historische Geologie H. v. Meyer 186 1 London , British (announcement o f Muscum (Natural find ) Histo ry) R. Owen 1863 (full description) W. Dames 1884 East Berlin , Museum fUr NalUfkunde der Hum boldtUnivcrsitat F. Heller 1959 Solnhofen. private owne rship H. v. Meyer 1875 Haurlem. Teyler (as a pterosaur) Museum J. H. Ostrom 1970 (as ArChaeopteryx) F. X. Mayr 1973 Eichstatt , J ura(provisional deMuscum scription) P. Wellnhofer 1974 (full description) P. Wellnhofer Solnhofen, 1988a (provisional Burgermeislerdescription) Muller-Museum P. Wellnhofer 1988h (full de\Cription)
15
Tile Solnhofen limestone
Today, the world-wide acclaim for the Solnhofen fo!>!>i b halo ensured that important fossils are either incorporated into the collect ions of the quarry owners or find their way into the hands of de;llers. To acquire a decent specimen of, say. a pterosaur would involve thousands of deutschmarks and an Arclweopteryx would be almost unpriceable! As fossils may even be an important part of the economy of the quarry, the working quarries exclude fossil hunters. There are various disused quarries , but fre sh rock is covered by debris piles which have been tho roughly scoured for fossils over the centuries. However, a few quarries have been especially designated as fossil quarries and here fresh sections are accessible and may be worked by amateurs. Although it is certai nl y less easy to come across fossils by accident than it once was this does not seem to have affected the popularity o f fossil hunting. In fact , this activity is so popular that entire German families will come to the region on fossil collecti ng holidays. For visitors to the area the magnificently situated Jura-M useum in Willi baldsburg , Eichstiill , houses the largest of the public collections. Also in the Eichstall area , at Harthof, is the private collect ion of the Museum Berg(!r . In Solnhofen itself is the Burgermeister-Mliller-Muscum as well as a large private collection open to the public at the Maxberg Quarry (Museum des Solnhofen Aktienvcreins). The Bavarian State Museum (Bayerische Staatssamm lung fUr Palaontologie und historische Geologie) in Munich is also well worth a visit.
2
Geological history and stratigraphy
Geological histor y of the Southern Franconian Alb rhe stratigraphy of Bavaria in southern Germany is relatively simple. The hcdding dips gently towards the southeast causing Jurassic rocks to outcrop over most of the Southern Franconian A lb (figs. 2.1-2.5). To the north and
northwest these pass downwards ;nlo Triassic sediments, whilst to the south ,lI1d southeast they are overla in by deposits laid down in the Tertiary Period. The o lder Pa laeozoic rocks, which arc metamorphosed and ridd led wi th igneous intrusions, underlie the area, but in the east are brough t to t he surface 111 Ihe fault blocks of the Bo hemian Massif. In Palaeozoic times these rocks formed parts of a series o f ancient mountain ranges which ran east-west across \()uthern Germany. These mountains were formed during a tectonic episode known as the Hercynian (Variscan) orogeny wh ich culminated late in th e l ';.rbonife rous Period at around 300 Ma. The mountain s were subject to t'rusion so that by the beginni ng of the succeeding Permian Period they had hee n worn down to expose their metamorphic and gra nite core. In the lu llowing periods these harder rocks persisted as a topographic high , known as the Vindelicisch Land , the position of which dominated regional palaeogeography until the e nd oflh e middle part of the Jurassic Period (see I1g2.6). Through tl nte the Vi ndclicisch Land subsided and began to be covered by sediments. In I arly Permian times conti nental sediments accumulated in the initial deprc\sions. Thereafter , as the land san k, the sea gradually transgressed southI·,j ... twards. To the northwest of the Southern Franconian Alb ma rine sedimC llts, such us Ihe well-known Middl e Triassic Muschelkalk, were deposited, " ll\: losing foss ils such as ce rati te ammonoids and oysters. In contrast. Triassic n lullc nts of the Southe rn Franconian Alb arc mostly non-marine sha les and ;lIllhlones, laid down in fluviatile and delta ic settings. lull y marine deposition over the entire area did not begin unlillhe Jurassic Pe riod when the Southern Francon ian Alb Illy under the shallow waters o r a WIde shelf sea . Sediments of Early Jurassic age (Lias) are dark shales and UI):ll1l1ceous (clayey) limestones and the period is often referred to as the Black I\IIU\..,;c . In the succeeding middle part of the Jurassic (Dogger) Period -I nd , lones prcdominate . and this interval is ofte n called the Brown Jurassic. \ .. t hI.' ,ca rldvanced du ring Middle J unNic times . Ihe coasHi ne migra ted 10 I he
17
Geological hislOfY fllld slrtlligmpity
Fig. 2.1 Outcrops of Jurassic rocks (stippled) in northern Europe. The inset shows the situation in the Southern Franeonian Alb and the section line of fig. 2.2. Adapted fronl Meyer. in Meyer & Schmidt-Kaler ( 1984) and Viohl (1985).
south and east but the palaeogeography was complicated by the developme nt of a northwesterly projecting spur of resistant land around Landshut with a corresponding indentation known as the Regensburg embayment. Conti nued incision of the Regensburg embayment into the coastline eventually breached the Vindelicisch Land ba rrier. The northern waters became connected to the sou therly Tethys Ocean and the Vindelicisch Land became an island . So it was th;11 by Late Ju rassic (MaIm) times, where the rock .. nrc often called t h e White Jurassic because of the llbunclancc of lir11(.' .. tOIli:'I, ll1l' \:on lin uing
Geological history of Ihe SOli/hem FrallCOlliuli Alb
F.anconlan Alb p.e -Alp
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Fig. 2.2 . Generalized geological section through strata of the Sout hern Franconian Alh, with map showi ng dept h in met res to the Palaeozoic basement. Adapted from Meye r & Schmidt-Kaler (1984).
ma ri ne transgression had comple tely flooded the Vindelicisch Land . The tn lluence of land now came from the north from the uprising ' Mitte ldeutsehe Sl.:hwelle' . For the fi rst time the Southern Franco nian Alb could exchange walcrs directly with the Tethys Ocean . However, evide nce from recentl y lh"i llcd boreholes to the south o f Munich (used in the palaeogeographic ICl.:onstruction of Meyer, see fig. 4. 1, p. 57) suggests that such an interchange of Willers would have been impeded by carbonate shoals which lay under o nly a h'w me tres of water on the northernmost margin of Teth ys. In this t ranquil 'I'l1 l11g orga nically mediated carbo nate mounds and reefs spread across the I ,u ho nate platform of the Southern Franconian Alb. Between the reefs lay "1l1ll 11 basins which were infi lled by light co loured limestones and argillaceous Ihllc'tOlles. These incl uded the Solnho fen Plattenka lk. luwards the ve ry end of the J urassic, deposition over the Sout hern FrancoIIl,tll Alh came to an end, as land emerged in the northwest and east and t he Il'Ihys sca regrcsscd to the soulh . Exposed until Upper C retaceous times , the Mn cllOic lIcdimcnts were then subjected to the actio ns of wind and weather. I hl'cl'lI fI Cr, there was on ly one , short further period of widespread marine ~, ,IU tlcnlnt io ll which took place at the beginning of the Upper Cretaceous (in 1111 (\:nomanian- Turonill n stages, around 95 Ma). The sea advanced fro m the "Il Il H: II ~ I , nooding the area from Ries to Regc nsburg and laying down I ttd ~ \( lII c~ li nd impure limcstones. Around Rege nsburg Ih is sedi ment is now
19
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Geological history of tire SOli/hem FraflCOfliafl Alb
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, •
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limestones. Deepest of all is the Altmuhl valley wh ich runs betwecn Dollnstein and Kel heim. Although the present-day A ltmuh l river is too small to be responsible for such largc-scaleerosion, unt il the late lee Age the valley used to guide the waters which now flow furt her south down the Danube valley. Throughout the Quaternary Period deep ground fros ts furt her weathered the rock. At the end of the Ice Age men began to colonize the valley. Theold caves in the valley sides provided protection and the A ltmuhl region is very well known for the many fi nds of prehistoric artifacts.
Palaeogeography and facies distribution in Late Jurassic times LaI C in the Jurassic Period the Southern Fra nconian Alb WU'I co ve red by a broad shelf sea which beca me progressively shallower [wet 1110 ,,' ]IInlll l cd (sec
Pa{aeogeogmplly alld iades distribution
d
•
Amberg
lig. 2. 7, regional palaeogeography for Late Jurassic times). To the northeast lily the Bohem ian Massif, to the north and northwest the eme rge nt ' Mitteldeulsche Schwelle'. and to the south a shallow-water platform , represe nti ng Ihe submerged remnants of the Vindelicisch Land , which limited exchange of wuh,:r with the Tethys Ocean . Channels con nected the waters of the Tethys Ocean with those of the Southern Franconian Alb and along these condu its (a mc Tethyan-type marine sediments and animals. The positions of these pu!>,agcs are uncertain but they are genera lly placed to the west and thus ubscured under recent cover in the Ries Meteorite Cratcr. TI1 C Solnhofen wa ter mass must also have been connected to the northern Boreal Ocean, hccllUse there are also rare boreal representatives in the Solnhofen fauna (Zc i~s 19(4). Fvcnls leading to the formati on of the plattenkalk basi ns began in Oxfordian times (~cc fig , 2. 901) . In the west the deposition of regularly bedded argill aceous lill\c~toncs. similar 10 tho~c of Midd le Jurassic times conti nued , and was
Geological history a"d stratigraphy
1
Ii
J MUl,f Centrele
Fig. 2.7 General palaeogeography of northern Europe in Late Jurassic times. The shaded areas represent landmasses from a shallow continental sea on {he m.ugins of the Tethys Ocean. The small box shows the position or the Southern Franconian Alb. From Viohl ( 1985).
followed by purer limestones, wh ilst in the east a differen t facies was developed (a facies refers to an association of lithologies which are the deposits of a certain sedimentary environment). Slight submarine highs were colonized by an association of plate-like siliceous sponges and encrusted by cyanobacteria, between which were trapped peloids (amorphous lumps of calcium carbonate , some of wh ich were perhaps originally faecal pellets), whilst at the same time lime mud (micrite) was deposited on adjacent areas of lower relief(fig. 2.8). On the highs, in the sponge-alga l beds, not only was calcium carbonate produced at a faster rate , but this facies was cemented at an early stage making it resistant to compaction relative to the adjacenl bedded micrites. A primary difference in relief between the sponge mound highs and intervening basins was thus acce ntuated. In most places the organically constructed mounds formed gently rolling submarine hills but where the mounds protruded more abruptly from the seafloor (as in the Kelheim area) chunks of debris occasional ly fell from the edge of the reef mass into the su rrounding bedded facies . Tn the Kimmeridgian stage the sponges proliferated (figs 2.9h. c & d and 2. 10) and the barriers o rientated along a NW- SE trcllll liprCu\1 ~h'w l y north-
26
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Fig. 2.8 Lithostratigraphy of the Southern Franconian Alb. Note how the growth of the sponge-algal mounds controlled deposition of the bedded facies. From Vionl
( 1985),
Geological history (l/id straligra"hy
OXFOROIAN
(ox,. 21
•
" Fig. 2.9 Palaeogeography of the Late Jurassic. The Southern Franconian Alb was a shelf area on the northern margin of the Tethys Ocean submerged under shallow water. During Late Jurassic times sponges colonized original highs in the underlyi ng topography, building mounds which accentuated the relief of the seafloor. Protected basins were formed between the sponge-algal mounds and in thcse bedded areas limestones wcredepositcd . (a) Oxfordian (OXl +2) - start of sponge-algal mound growth in the east, probably as a result of shallowing. (b) Early Kimmeridgian (kil ) - sponge-algal mounds spread westwards. (c) Middle Kimmeridgian (ki 2}- spongegrowth reaches a climax and adjaccnt sponge-algal mounds fu se 10 leave intervening basins. (d) Late Kimmeridgian (kil ) -watcr shallows further. SpongesspreaJ to the bottom orthe basins and appear in the bedded facies. Plattenkalk starts to bc dcposited in the east. (e) Early Tithonian (t~) - Plallenkalk is dcposited over most of the Southern Franconian Alb. (f) Latc Tithonian (tiJ) - sea starts to retreat and land emerges to the north. Planenkalk is still deposited in the south. From Meyer & Schmidt-Kaler (1984) and from Meyer in Meyer & SchmidtKaler (1984). wards. The chai ns fused into a network e nclosi ng small basins which gradually sh rank in size as they were overgrown by the rapidly accreting sponge mounds. The basins were first filled with bankkalk ('Bankkldk ') , i.e. thick (dm to m) regularly bedded limestones , often rich in ammonites and with slight ly undulose beddi ng pla nes. Bankkalk , like plattenkalk, has occasional th in intercalations o f argillaceous limestones. The sponges spre
28
Puilleogeography and fllcies distribution
I AALY KIMMERIDGIAN
Ikl"
...,..,......... I .;\ ':J ' ........ .... ""'' 00... "_,_ I .... ' ... .
,
'.
If! .
'm
, "iI '.........,
I . .. " ............, ....
1~
_
_
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.
'm (Fig. 2.9 parts d- f on pp. 30-31)
..
Geological history and stratigraphy
LATE KIMMERIDGIAN
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,....... ..........
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!3 ThIn" bo.do~
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30
Palaeogeography and facies distribution
I Ar e TITHONIAN HI, 1
J ___,_ u
,- ,--__,_ ~
-..---
.Wolo ..nD\l'lI
•
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I'll! . 2. 10 Kimmeridgian sponge- algal mounds exposed along the banks of the AItunlhl neur Snlnhofcn. This facies weathers to form the cliffs and pillars. These are I.l1tlWn loclilly a~ the 'Z wtil/-Al'osld- Fdsel/'. From Meyer & Schmidt-Kaler (1984).
..
Geological his/Qry and s/f(lfigraplry
Fig. 2. 11 Ammonite rol1marks from Paintcn; approxim ately half natural size; BSPH GM 1950 XXXV 15. gcnerall y of cyanobacterial o rigin). There are also algal tubes, known as tu biphytes, ooids (smaller, rounded millimetric size calcareous grains which only form under conditions of fa irly high energy), oncoids (spheroidal structures bounded by algae, gene rally req uiring occasionally agitated water for form ation), encrusti ng fora minife ra (unicellular o rganisms building calcareous shells), as well as ammo nites and much bioclastic debris. By Late Kimmeridgian (ki l ) times the water must have been quite shallow and wave motion fa irly strong. Sedimentatio n was irregular, beds wedge o ul , and there are small unconformities whe re the processes of sedimentation we re interrupted . In the reef facies horizons of o ncoids, ooids and fin ely laminated (and wrinkled) stromatolites were formed. Another probable consequence of the shallowing was that the sponge mo und facies began to be re pl aced by the bedded facies in t he cen tral pa rt of the area. wh ilst in the cast. ncar Kelheim, com ls and hydrozoans Colonized the tops of sponge mouml.. The corals evident ly built a st ronger reefal framework than did the "pl1n~~' .. ,ifill till"! gave
32
Palaeogeography and facies distriblltiOIl
Fig. 2.12 Marks made by models of pcrisphinetid ammonites rolling over wet mud . Photograph by B. Kleebcrg. greater support to thei r accumulation . Thus the coral reefs grew steeply upwards, resulting in a na rrow zone of growth mantled by a wider a pron of debris. With the shallowing of the water and an increasing importance of coral ree fs liS a ba rrier to the Tethys , the patte rn of sed im entat io n began to change and th e lirst platte nka lk was deposited in the eastern areas, a process which was to culmi nate in the deposition of plattenk alk at Solnhofen . Plattenkalk differs from bank kalk in the highly planar and much thinner (1-30 cm) nature of the bedding, although both plattenkalk and bankka lk may have thin intercalated beds of lIrgill aceous limestone. The first major plattenkllik developme nt occurred in Middle Kimmeridgian times ( ki 1) , far to the east at Ebenwies. The facies then migrated westwards as a response to th e regiona l sha llowin g. By Late Ki mmeridgian (ki3) times plattenkalk was being deposited at Pai nten and Kclheim. A lthough supe rficially similar and with some beds containing exceptiona lly well-preserved foss ils, overall this plattenkalk shows major differences to that of Solnhofen . The re is a high concent ration of preserved orga nic matte r. which is often concentrated in layers of chert (' Hornstein'). The chert was probably derived from sponge spicules or planktonic radio larians (unicell ular microorga nisms which secre te a skele ton of silica). This, together with the cuncentration of organic matter, indicates a high marine productivity (a nd as the Solnhofen area was not adjacent to any substa ntial land area the organic Illattercan not be terrestria l in origin (sec palaeoecology, p. 73). The li mestone fah n c also contains numero us coccoli ths (the C
Geological history and stratigraphy
These earlier plattenkalks (of ki2' ki) and til , laid down before the main phase of plattenkalk development in tii) were probably deposited in an environment less isolated from the sea and more biologicall y productive than that of the Sol nhofen Plattenkalk . T he proximity of the coral reefs has also influenced the facies , most obviously as a source of detrital sediment which is interbedded with plattenkalk. In particular, as the reefs we re flank ed by steep slopes , sediment-laden currents could roll downwards depositing turbidite beds in the basin (Schairer 1968). The turbidite beds are graded and may show erosional structures at the base. These include scratches , gouges and impact marks excavated on the already consolidated seafloor by larger particles entrained in the flow. The underlying sediment was also scoured by local eddies formi ng hollows infi lled by the turbidite sediment and now preserved in positive rel ief on the overlying infill as fl ute casts. Disc-shaped ammon ites were bowled along in the strong currents (figs. 2.1 1 & 2.12). When the flow fi nally came to rest the larger particles, including the foss ils and other fragments , were dumped first and covered by successively finer sedi ment producing the graded bedding diagnostic of such deposits. Plattenkalk became more widespread as a facies from the beginning of the T ithonian stage. By this time the sea was sufficie ntly shallow and water exchange with the Tethys so restricted that conditions were no longer favourable fo r sponge growt h. Corals had recolon ized the tops of sponge mounds, forming a thick barrier in the east and isolated patch reefs to the south. As the sponge colonies died, leaving only the narrowest areas of sponge growth, the bedded facies encroached on the mounds. A map of the Southern Francon ian Alb in Early Tithonian (ti 2) times (fig. 2.ge) shows a shelf covered by the sponge mound mass and peppered wit h small basins. That these Early Tithonian facies were deposited in an envi ronmen t which became increasingly restricted as time progressed is demonstrated by Keupp's (1978) st udies of the microfacies. The rocks deposi ted in the ea rly Early Tithonian (til) begin with a red marl layer , the so-called 'ROle Mergel Lage' , a disti nct marker horizon throughout the western area. It con tai ns an abundance of recogn izable plankton , mainly coccoliths and radiolarians, the latter contri buting towards the chert horizons that pervade the limestone beds. The coccoliths are fair ly well preserved and most probably originally lived in the overlying waters. T he coccolith asemblages of the Red Marl Layer show that certai n lami nae are dominated by one species, CyclagelospJ/aera margereli. At these times the environment must have been too hostile for other species. leaving only those which were the most tolerant to the extremes of sal inity and temperature to inhabit the increasingly isolated ' lagoonal' waters. Moreover , because the coccolith assemblages are distinct from one thi n lamina to another, this indicates an absence of bioturbation and macrobenthos from the stagnant bottom waters. A relatively high productivity of organic matte r ( ill comparison wit h the Solnhofen Plattenk" lk) led to anoxic. sulphid ic c ()ndltlon ~ in Ihe
Ptllaeogeography and facies distribwioll
til
...,
Morniheim
T
T
• ~.
,
.
I
Krumme Llge
Upper Solnhofen Plattenkalk Krumme lag.
lower Solnhofen Plattenkalk Aogling Beds
~,I it1
i'
Fig. 2.13 Lithostratigraphic and biostratigraphic subdivision of the Tithonian beds in the Solnhofen- EichSliitt area. ~tag nant
bottom wale rs with the production o f pyrite. It is the oxidation o f this pyrite wh ich has produced the red colour of the bcd.
Somewhat surprisingly the e nvironment seems to have been less hostile when the first plattenkalk was deposited in the Solnhofen-Eichstatt area (see lig. 2.13 for t he strat igraphy o f the T ithonian beds in this area). Th us t he l i2 .. 'age sees the development in the Lower Solnhofen Plattenkalk (li23 ) o f a u nit known locally as the 'Spllre"schiefer' (literally trace fossil shale, although it is in effect a thinly bedded limestone). T his unit is more thin ly and less regula rly bedded than the Upper Solnhofen Plattenkalk . co ntai ns chert horizons and is hlled wi th mottled, transect ing ma rks thought to be trace fossils. These t rnces, w mbi ned wit h an irregu larity in bedding and an absence o f fi ne lamination , ~lLggest that occasionall y macroben thos lived in the sediments of the basins. Iluwever, actual body fossils arc rarely found. In the later part of the Early Tithonian state (ti Zb ) the plattenkalk reached Ihe height of its developme nt in the Solnhofen- Eichstan area when the famous Upper Solnhofen Plattenkalk was laid down. The limestone is renowned for its p];mar, regular bedding and its pu re carbonate composition as well as for the c'(ccptional preservation of its foss ils. In contrast to both the overlyi ng (M(irnsheim beds) and underlying (Lower Solnhofen Plattenkalk) facies there I~ ulmos! a complete absence of sponges and radiolaria so there are no chert hOflJ;lln'i. Few Illicrofossils arc recognizable inside the limestone beds, whereas III thl! more clay-rich intercalations beautifully preserved coccoliths occur,
....:::... ~..
,.
Geological history and stratigraphy
Fig. 2.14 Trennende Kru mme Lage bed in the west wan of the Horstbergquarry, ncar M6rnsheim, south of Solnhofen. This slumped unit overlies the Lower Solnhofen Plattenkalk. (The Upper is thinly developed in this area.) At the top of this outcrop is bedded limestone of the M6rnshcim beds. From Meyer & Schmidt-Kaler (1984).
some of which are still articula ted as coccosphe res. These organisms probably grew in the lagoonal water, the hostile nature of which is demo nst rated by the impoverished assemblages of coccoliths and foramin ifera in terms of species and numbers. As elaborated in chapter 4, most of the carbonate of the limestone beds was not formed in the essentia lly sterile lagoon but in the open sea by plankton and by the corll l reefs. T he marine carbonate ooze was resuspended by storms and transported over the reef with only the small est particlcs being carried liS far as Solnhofcn. The fine sediment rain ed down onto an irregularly cnnh!url,'d hasin
36
PlIllleogeograpliy and facies diSlriblllion
floor. In the Solnhofen-Eichstatt area, the gradient of this surface was not sufficien t fo r the sedi me nt to be destabilized by storms, and the plattenkalk beds are not thought to be redeposited by turbidity curren ts. (This had been advanced as a depositional mechanism and is discussed on p. 68.) It seemed to require a distinct shock to shift the semi-consolidated ooze and such events are recorded in the' Krllmme Loge' beds, slump horizons which both underl ie and overlie the Upper Solnhoren Platte nkalk (fig. 2.14). The Krumme Lage beds are composite, some 5-15 m thick and e nclose a sequence of irregularly fo lded and some times broken units. The events which caused the sediment pile to collapse downslope were synchronous throughout a wide area and are best a ttributed to earthquakes. It was suggested by Keupp (1977b) that the occurrence of these slump horizons may be con nected to movement a long faults, which also affected water depth and isolation of the lagoonal waters. Although the Upper Solnhofen Plattenkalk marks the top of the seq ue nce at Sol nhofen, in the Eischstatt area plattenkalk continued to be deposited until later in the Late Tithon ian (ti3) (fig. 2.91), where it is included in the unit known as the Mornsheim beds. In contrast to the Upper Solnhofen Plattenkalk, the Mornsheim beds are rich in ammonites a nd biva lves, fragmented by wave action. Coccoliths are also common and some portions of the beds are siliceous because of the presence of rad iolaria and sponge spicules. T he sediments contain pyrite and the siphuncles of a mmonites preserved in a black phospha tic material (so-called' Sipho-Erlwllllllg' which also occurs to a lesser extent in the Upper Solnhofen Plattenkalk) probably representing the bui ld-up of anoxic conditions within the sedimen t due to a higher organic inpu t. All this seems to indicate that con nections with the Tethys Ocean had become re-established. Another plaltenkalk from rocks of ti3 age comes from Dait ing, southwest of Solnhofen, and is well known for its well-preserved reptiles. In the southwest, between Monheim and Neuburg, plattenkalk was laid down at several intervals in the ages t i2-6' East of the Solnhofen- EichsUitt a rea, in the Late Tithonian , there were accumulations o f bankkalk, as well as deposits of argillaceous limestone and ' paper shale' (' PapierschieJer', or finely fissile argillaceous limestone). By the very end of the Tithonian (ti 6), marine deposition was evidently nearing an end and there is a clear coastal innuence to the deposits as the sea retreated to the south.
3
Petrography of the Solnhofen Plattenkalk
Lithology in the Solnhofen-Eichstiitl area The most striking feature on e ntering one of the quarries in the Solnhofe n Platten kalk is the extraordinary regularity of the limestone. The beds are tabular and can be traced ove r several tens of metres with no change in their part icular properties (colour, frac ture, inte rnal subdivisions a nd thick ness) , so much so that qua rrymen can recognize individual beds and have even given them names (Edlinger 1964). O n a scale of kilometres , between di ffe ren t quarries, the thickness of the beds varies. Where the plaucnkalk is not th ickly developed , such as at the edge of the shallow Eichstatt basi n at Sche rnfeld , the beds occur in packets oflhin sheets, each about 0.5-1.0 em thick (fig. 3. 1). In a reas whe re the limestone accum ulated to a greater th ickness , as around Sol nhofen itself, the limestone beds form units up to 30 em thick (fig. 3.2). These slabs arf': quarried for use as lithographic printing stones on account of their thick ness, pu rity and hardness. The slabs of pure micri tic limestone, given the name of 'Flill z' by the quarrymen (plural 'Flinze', English adopted term , 'fli nz'), may be interbedded by thinner (usually 1-3 em thick) fissil e, shaly laye rs, termed ' Faille' (plural 'Fillilell', English adopted term 'fa ule'). Typical flinz beds are composed of a very pure calcium carbonate (95-98%), with onl y very minor proportions of clay (up to 3%) and quartz (up toO.4% ). In contrast, the typical Hiule consists of 77-87% calcium carbonate , the rest being predomi nately clay (10--20%), with a small amount of quartz (a round 3%) . Lithologies inte rmed ia te in physical and chemical prope rties between faule and fl inz are also known, and given names such as ' Bliifferjlillz' or 'zaIJe Faule'. Stacks of flin z split into individual sheets along bedd ing pla nes, which are defined by surfaces where there is a conce ntrat ion o f clay minera ls. Although flat , flin z slabs are not smooth, but slightly roughe ned , with the underside of the slab having smooth 'crenulations' , whilst the topside has sharper ridges (fig. 3.3). These roughe ned textures may have fo rmed during the de-wate ring of the sediment (Mayr 1967), or at a later stage in diagenesis. TIle difference in texture , which is most obvious in the purer and thicker beds, is useful ht:cause it gives a n almost infalli ble crit erion for Ihe way-up o f a slah . W Cl1 lhct'cu su rfaces o f ftinz lire a light yellow-white in colour and Ihe l>ecb bn::lk wilh II l'lluchoidal 1
Lithology in th e Soltrh oJen- Eichstiilt arera
h g. 3.1 Eichstan plattenkalk facie s at Neumayer quarry, 500 m NE of Schernfeld . I hc beds arc typically 0.5-1.0 em thick and separated from cach olher by clayey p.!ftings. From Meyer & Schmidt-Kaler ([984).
frac ture to display a darker, beige-grey interior. Sometimes beddi ng planes I1 lay show other colou rs, such as concentric bands of yellow , brown o r grey , or the beaut iful fern-like markings called dendrites. Despite the plant-li ke llppcant nCe, these dendrites arc inorganic fea tures caused by a solutio n of the \ 111i1 11 amou nts of iron o r manganese from inside the beds and their reprecipiIII lion
Petrography of the Soillhofen Plattenkalk
Fig.3.2 SOlnhofen plattenkalk faci es at the MlIxberg quarry. Soln hofen. The thick micritic limestone beds (flinz) may re
leaves which can be pee led apa rt. Beds of fiiule weather recessively in the profile, so leaving the layers of flin z outstand ing.
Occurrence of macrofossils F1inz beds split apart along shal y partings and the fossils, when they are found , are almost always located on the underside of the slabs. The thin , microfossilcontaining shaly lamina also sticks to the underside of the overlying sl.-b . It might be suggested that the reason foss ils are only found o n bedding planes i!. that, even if they were present inside the beds, the well-indu rated flin z :,labl> would not readily part to reveal them . However. certain peculiarities o f fos!>il preservation cou nte r th is argument: fossils which show l-ofl -parl preservation arc almoSI invariably accompanied by a depres... lOn III Ih1.' hc{jdi n ~ pl;U1C surfaces for several centimetres over the fos., il .... In Ihe I ltll·l· ... \· UI tit Ihe (o... ., i!!.
Grains and microfossils
I I~
Flinz slabs from Maxbcrgq uarry, Solnhofen. The upper and lower slabs show ridges of the top surface of a bcd whilst the middle one has the gentle undulations of a lower surface . Photo N. H. M. Swinburne . From Swinburne (1988) . "'I'I\l
l lil' .. harp
I1U"lOg an early concretion of the surrounding sedime nt . the o pposite effect is plllduced , and a bulge occurs o n the overl yin g bedding pla ne surface. These [.".. it>; would therefore certain ly be visible if they were inside the slabs o f Oinz. Ilwldenlal ly, the few fossils which have been fo und inside fl inz beds can show a ullCrbly detailed preservation . I
Grains and microfossils liulh mnz ;111(\ fiiu le are so fi ne-grained thai Ihe electron microscope is needed hi decipher the nat ure of Ihe carbona le part icles . Such observalions show th at gtalO .. 11\ the mnz have to a large extent recrysta ll ized , or are obscured by ( ',,("0, o vergrowths. with the cavities be ing fill ed with ccment (a ltho ugh th ere I~ 'lu ll II ~ lI ffici c nt porosity (7- 12% ) to lJ lIow t he Slo ne to lake up ink in IUhography). A ~ rc al c r deg ree {)f sucees'I in the micro<;(:opic study o f t he
Petrography 0/ the SOl/lito/eli Plattenkalk
Fig. 3.4 Dendritic markings around a fish; Gyrodus sp., Eichstiitt; maximum diameter 59 mm. IGPTUB , photo by B. Kleebcrg.
sediment particles has been obtained from the beds of fau le and o ther shaly intervals, which are largely uncemented, and retain an original porosity o f 1426%. It has often been assumed that the ca rbonate in the ftinz was o rigi nally the same as that in the Hiule, but alte red beyond recogn ition by d iagenesis . This assumption is supported by investigations of the grai n size of disaggregated ftinz and faule (Flugel & Franz 1967, Keupp 1977a) in that both ftinz and fau le show the same major peak of 1-3,um in the grain size distribution curve (fig. 3.5). The first microfossi ls lO be fou nd in the faule were fora minife ra, discovered at the end of the last century. These benthic foraminifera (all with calcareous shells the size o f fine sand , made by unicellular o rgan isms wh ieh lived on the seafloor , see fig. 3.6) were described by Groiss in 1967 using light microscopy on samples of disaggregated faule (see also comments on the natu re of the assemblage, pp. 73-4). Assemblages of coccoliths (micromctrc-sized c,llcareous plates which were originally the covering shields of a un icellul ar algll. called a coccolithophorid) were described by lise o f the electron micro1>(opc hy KClipP (1977a) from the fiiulc and o ther shaly I,uninae (fij,t . 1 1) I hl'Y OCcur
42
Grains and microfossils
" "
FUNZ
a
" "
,
"
"
,
4
S
6
1
Particle size, j-Im
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,
. >, FAUlE
b
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,
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,
,
Particle size, pm
,
,
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Fig. 3.5 Size frequenc), diagram of partide size of disaggregated plattenkalk . (a) F1inz from Maxberg quarry , Solnhofen; (b) fiiule from Schcrnfcld. From Kcupp (l977a).
Fig. 3.6 Plattenkalk foraminifera. (3) GUlidryina bllkowiensis Cushman & Glazcwski ( X 42) ; (b) Nodosaria ellglyplw Schwager (x22); (e) Margilllllina
~
~ e I
dislorla Kusnetzowa ( x 40) ; (d) Quillqileioclilino. egmonle1lsis Lloyd (X45) ; (e) Patellina [eifeli (Paalzow) from
above (left) , from below (right) and from the side (above) . From Groiss (1967).
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Fig. 3.7 Electron micrographs of the microfacies of the faiile (argillac eous limesto ne beds) . (a) Isolated coccoliths ; Zeugrha bdotus , Stephano/ililio n , Ellipsag elospllaera and Cyc.lage/osphaer a from the Upper Kimmeridgian (ki ) at Painten ; field of view 14 JIm . l (b) Coccoliths in coprogenic aggregates; Slephall o/itirion bigo li Deflandre; fi eld of view 31 Iml. (c) Coccoliths in coccosphere; Ellipsage/osphaera keftalre mpti Grun ; view c. 13 ~m. (d) Calcisphere; Pithonella gustafso ni Bolli fro m the surface fie ld of of a faule; field of view 28 Jim . (e) Coccoid cyanobacterium ; fi eld of view 28 Jim. (f) Rows of coccoid cyanobacteria concentrated along certain bedding planes. Fro m Keupp (1977.) .
,
I', ""'~"'I'II, ,,/111,- \,'Iu/"',,·,, ,'/otu.'IIJ."IJ.
prcdominarllly in i~ola t ed aggregates somc 50-100 pm in size (fig. 3.7b) , suggesting perhaps that they arc the remai ns of faeca l pellets produced by animals such as crustaceans. Smaller accumulations of coccolit hs. each having the same shape and so derived from a single species. may represent the ill situ dccay of a coccosphere (fig. 3.7c). Keupp also documents the occurrence o f 'ca1cisphcres' (fig. 3.7d). very regula r sphe rical shells with a wall of radi ating prisms (a nd quite disti nct from the coccoid cyanobacteria, detailed be low) which represent the cysts of calcareous dinoflagellates. (These a re anOlher group of protists named after the (unpreserved) pair of flagellae which they used for propulsion ; the cysts are the resting stages of the life cycle.) The recrystallized remains of Rad iolaria (protists with siliceous tests) are e ncounte red on ly very rarely . Ostracods, submillimctric-size crustacea ns, were described from the plallen kalk of the Langcnaltheim area by Gocht (1973). The ostracods are preserved with bot h valves at right a ngles to the bedding (i. e. in life position). but are now crushed by the subseque nt compaction o f the sedime nt. Ke upp (19773 , b) has also described a suite of sphe rical cavities from the faule which have an ex te rnal dia mete r 8-20 l,m , some times as much as 30 1,m. According to Ke upp, these cavities have a wall , typically2--6Jl m thick a nd built o f rounded crystallites, each betwee n I and 3 Jim in diameter (figs. 3.7e, f). The inte rnal di amete r suggests it once e nclosed a small cell and this cell probably secre ted calcite rather than aragonite (there being no evidence of any widespreild dissolution of unstable ilrago nite which wou ld have infilled the cavities, norof any relict aragonitic texture in the shell wall). These two linesof evide nce suggested to Keupp that the sphe rical shells were secreted by the activities of coccoid cyanobacte ria. Ke upp considers that the cyanobacteria we re the major contributo rs of the faule carbonate because they are present in all mule beds from the Solnhofe n- Eichstiitt area and even whe n the sphe res the mselves are nOi visible by use of the e lectron microscope the crystallites which make up the spheroid wall correspond closely in size to the measured grai n size peak of I- 311m. Others have pointed out that the walled cavities could be entirecoccosphercs (which would have a very similar diameter) with the individual coccolith plates too altered by recrystallization to be recognizable. In refutation o f this suggestion Ke upp (pers. comm . 1986) points out that rathe r than rounded crystallites which onl y to uch at points , a syste m of interlocking plates should still be visible in the walls of broken sphe res. Ke upp ( 1977a) argues that although the mice lles (the c rystals which make up the coccoliths) are of the appropriate dimensions ( 1.5-3 /lm) , disaggregated coccoliths canno t be responsible for the grain size distribution for the following reasons. If the two coccoliths most common o n the bedding planes o f the Solnhofen PllItlcnkalk. E/lipsagelosplwera and CyciagelosfJlwera. disOlggrcglHed thc)' would produce micelles of two diffe re nt sizcs. Thosc deriveu from the inm' r whllrl \\1111111 be
46
Graills ami microfossils
n lllldimc nsional (less than 1 Jml in size) and would dissolve under the weakest prc'>Sure solution. The resulting sol utio n would repreci pitate directl y o nto the 1.lrgc r micelles which , although originally 1.5 x 311m , would grow in size as l" ald te precipitated in optical co nt inu ity. accum ulating preferent ially in t he direction of the c-axis of the crystal so tending to elo ngate it . In th is way the H::-.ulting rectangular grains wou ld be long and thin , measuring about h x 111 m. If, for some reason , the calci te which precipitated o n the la rger micelles precipit ated o n the sides of the gra in tending to make it eq uidime n\ Iunal , then the resultant particle would be too la rge (at 3-4/l m) to accoun t for thc observed gra in size distribution . Finally, if in the unli kely event that the coccoliths, made of stable low-Mg calcite , suffered sligh t dissolutio n , \11 mak ing them into rounded particles, then they would be too small in \ I/C.
Within the faule , Keupp distinguishes carbonate laminae which contain these coccoid cyanobacterial cavities from the more shaly lam inae which ..:tmtain the dive rse microfauna. Indeed . Keupp regards the faule as a seq ue nce of the shaly bedding plane laminae inte rbedded with thin carbo nate laminae of the same composition as beds of true flinz (sec Keupp' s diagram o f cyclicities, lig. 3. 8). Others co nside r this alternation within the fau le as a seconda ry phenomeno n due to diagenesis. There is a di vergence o f opinion as to what constitutes the ft inz (sec plates o f u,>ual ftinz appearance unde r the e lectron microscope , fig. 3.9). Many investi~, H o rs have observed what they claim to be the remains o f coccoli ths, ofte n disaggregated to single micell es , and showing to a varying exte nt diagene tic rccrystallizatio n and overgrowth . However, estimates of the proportio n and dist ribution of these coccoliths varies greatl y between different authors. Fo r example , Fli.igel & Franz (1 967) estim ated there to be 500 000 coccoliths per nlln 3 . In contrast, according to Ke upp (pers. comm . 1986). coccoliths make up . 1 ve ry mino r fra ction (some 1%) o f Hinz beds. Yel they attract atte ntion hccause they are concentrated alo ng certain lamin ae in t he ftin z which a re nunor planes of weakness. Keupp be lieves thaI, as with the Wulc. the bulk o f the l1i nz carbonate was precipitated i ll Silu by microbial activity. In the Rin z, unlike in the fa ule , the moulds o f cyanobacte rial cells are no t usually recognizable because the cavity of the ce ll has bee n infi lled by cement. Th is blocky cuhcdral cement within the sphere breaks up on disaggregation to produce a tail on the flin z grain size graph o f particles up to IS Jim diameter. In additio n to the presence o f coccoliths. some larger particles have been ubserved in units of flinz (fig. 3. IOa). Although still within the size range of micrite . this somewhat coarser fractio n is te rmed ' reefal debris' by He ml ebe n ( 1977). He has observed fragments of fo ram inifera , bivalves. gastropods (with the brickwork -like texture o f origina l aragonite remai ning although no w Illtcred to calcite). ostracods, holo th uria n scJcrites a nd o ther echinode rm rc maim . Under the light microscope the larger particles can be sec n 10 be
Pelrography of Ihe Solnhofell Plattenkalk
,
fiule !. rgill'CIKIU' Nrn. .tonti Coccoli th . Rocogni .. ble CGCcoid cv.nOble terle
Fig. 3.8 Distribution of recognizable coccoliths and cyanobacteria in profiles from the plallenkalk at Schernfeld. From Keupp (19TIa). aligned in bands. Although usually planar, occasionally the lamination shows patches of small-scale cross-lamination (at least in some of the thick ftinz of the Maxbcrg quarry , Solnhofen , fi g. 3. lOb) demonstrati ng the variation in e nergy conditions at Ihesi te of deposit ion. Hemlcben also recorded 11 disruption o f the lamination and the occu rrence of dark blotches which probabl y represent small-scale biot urbat ion (fig. 3. IOa). Some fti nz units from !he Solnhofen Eichsliitl area may show coarser particles al the bottom u f a hed ~r:l ding to fin er particles . many o f them coccoliths. at the tOp
48
Diagcncfic o{leration of the sediment
I'lg. 3.9 Typical appearance of Solnhofen Plattenkalk under the electron microscope. P!l,;ture of the underside of a slab of flinz from Willlershof, EichstiiH. Note the reticulate ]laHern of ridges with a few scattered coccoliths. Scale bar 10 11m. Photo N, H. M. SWll1 bume .
Diagenetic alteration of the sediment 10 recap the propert ies of the fli nl.: this e ffectively pure carbonate is extreme ly Illlc-grained and seems to have been severely alte red during diagenesis. Even wtt h the electron microscope , it is very difficult to see any shape or texture in the carbona te grains which would reveal their origina l form . Wh ilst most of the part icles are probably the broken remai ns of coccoliths which had accum ulated 1111 the seafloor. others would have been the finest of the abrasion prod ucts derived from the reefs. The more clily-rich raule may have had an additiona l '\ Iurce of carbonat e, that produced in sim on the lagoon floor by cya nobacteria. Indistinguishable to the eye, diffe rent grains of calcium carbonate may differ HI mine ralogy and che mistry. There exist two main varieties of calci um l'lIrho nat c, cnlcit c and ur:lgonit e, each with ,I diffe rent crystal structure. Bo th lIlay form nt the curth 's surface, but aragonite is metastable and in the
Pelrography of tire Sol"lrofell Plallellkufk
50
Diagenetic alteraliOl1 of the sedimellf
Il;I rticula r physical and chem ica l conditions e ncoun tered during buri al, a rago!lite is transfo rmed to the more stable fo rm, calcite. Both mine rals are slightl y Impure calcium carbonates which incorpora te other similarly sized a nd cha rged 2 hillS Into thei r crystal structure in the place of the C a + , most especia lly Mg2 + . MCiisurement of the magnesium conten t of biologicaUy as weUas inorganicaUy produced calcite defi nes two gro ups of calcite, a low-magnesiu m (Mg <3%) and a high-magnesium ( Mg >3%, some times as much as 25%) varie ty. I )l;Igenesis is driven by the relative che mica l instability of high-Mg calcite a nd aragonite with respect to low-M g cakite and it produces physical changes in the ~~'di m en t fa bric. As the mud ooze o f the pla tte nkalk was compressed, the carbona te grains t,UTle into contact a nd ultimately, under sustai ned pressure , they dissolved at thl' contacts by the process of pressure solution. The pa rticles became welded ullo a sturdy. supporting framework . Po inted a nd protruding corners were n,pccia lly prone to dissolut ion , and originally angular pa rticles (such as the Iccla ngul ar crystals of coccoliths) became rounded . SmaU low-Mg calcite Iragments, togethe r with a ny a ragon ite a nd high-Mg calcite, whic h we re also Idatively unstable, e ithe r recrystaU ized o r dissolved . This provided a {'(lCO l -rich flui d which could precipita te as overgrowths (usua Uy in cont inuity wit h the existing crystal st ruct ure) or migrated through the CaCO l fra me wo rk , ilnd Infi lled the cavities with a blocky ceme nt . Late r , some rhombs o f do lomite IC:ICOl. MgCO l ) grew withi n the sedime nt. T he rhombohedra l cavities in '(} IllC fl inz beds a re cl early holes where dolomite crystals have been d issolved away (e.g. Ke upp ( 1977a), p . 70, pI. 24 , fi gs. 1-3 a nd Mause r ( 1988» . The ne t fl', ult o f these diagene tic processes was to conve rt a oncc soft sedime nt into a rompact a nd tough rock. Whi lst the fl inzcarbonate re mains some thing o f a n e nigma, in the raule well prese rved carbonate microfossils ca n be clearly seen. The diffe re nce in preser\'Ht lon between those coccoliths found in the fl inz a nd those in the cau le can l1H1l1l ly be a ttributed to the highe r clay conte nt of the raul e (bu t the re may be lit he r sedime ntary diffe re nces). T his preve nled the calcareous particl es fro m pre~s i ng aga inst each other a nd the clay also reduced the permeability o f the Ilcd. I)ore fl uids could nOl pene trate unfilled voids be twee n the microfossilsa nd precipitate overgrowths o f CaCO l . Conseque ntly the faule now has a higher r()f()~ ity than does the fl inz. rhe la mina tions in the fiiule a nd to a lesser exte nt in the flin z have been en hanced by the effects of pressure solution (see fi g. 3. lOb). F1inzlfau le hnundaries a nd the surface o f the fossils have also been affected . Pressure h ". 3. 10 Optical micrographs of Solnhofen fli nz. (a) Dark blotches re prese nt biOlurh;lIiol\ hy ('110m/riles; the light-coloured particles arc larger pa rticles of reefal debris ex 1() . (b) Lamimllion , plll n
IIcmlchc.n {l977) .
Petrography of tile Soillhofen Plallellkalk
solution of the carbonate was concentra ted along a bedding or a laminatio n surface across which the re was a change in solubility of mate rial , perhaps due to diffe re nces in particle size o r mine ralogy. Any insoluble residue, such as the clay. remaining after d issolution of the carbonate compacted togethe r to fo rm a n irregul ar surface. In section this is see n as a thin jagged line, known as a stylolite. The greale r the number of solutio n surfaces, the more carbona te has been re moved , so increasing the pe rcentage o f clay still furth er. The contrast betwee n almost pure micritic flin z a nd ma rly fii ule must ha ve been he ighte ned by such diagene tic effects, but the exte nt o f this process re mains uncertain . While Ke upp claims the effect to be minimal , He mleben ( pers. comm. 1986) suggests that migration of carbonate o ut of faul e into the flin z beds could have led to substantial inc rease of ninz thickness . Ot he r smaller-scale cyclicities may also be diagene tic in origin . In particular the rhythmic alte rna tio n of clayey a nd carbona te laminae within the faule, comme nted upon by Ke upp , may be the result of a seconda ry separation o f the compone nts. Similarly Ke upp's observIII'ion of a restriction of coccoliths to di stinct bands in the flin z is, in He mle ben 's opinion , merely a conseque nce of coccoliths be ing obscured by diagenesis elsewhe re in the flin z.
Redistribution of elements The now lithified limestone consists almost e ntirely oflow-Mg calcite, but there are still indirect methods to establish the original types a nd origins of the calcium carbonate particles. Thegeochemical argume nts used by Veizer (1977) to estimate the original constitution of the sediment were based on the distribu tion of the element stront ium wh ich. li ke magnesium , is a minor impurity in the calcium carbonate lattice. In the crystal struc ture of aragon ite more strontium is permitted in place of calcium than can be held by eithe r high Mg o r low-Mg calcite. Conseque ntly, whe n this aragonite is dissolved duri ng diagenesis it will e nrich the pore-waters in stronti um . If the fluid reprecipitate!o as a pore-filling ceme nt it wi ll have a high-Sr composition. So a sedime nlthilt origin ally contained some aragonite, but has now bee n comple te ly alte red to calcite. would be e xpected to contain a highe r conce ntratio n of stro ntium th:1I1 would a sedime nt deri ved fro m a high-Mgcalcile alone , if tha t sedime nt mc rely redistributed the ele me nts intc rnally . Howeve r, in rea lity the sedime nt and pore fluid s do not form a self-contained che mical syste m. Duri ng diage nesis the re is some che mical exch,lIlge of po re wate rs with o the r rese rvoirs. These rese rvoirs include the ove rlying seawate r and marine or fresh ( me teo ric) wate r trapped in the po re~ in the overlying rock formati ons. During such exchange: much of the ~ tro ntlUIl1 (a ... well as mag nesium) in the po re wale rs ClHl be lost to the sy~ t c lII 'I II 1I ...... 1.!~ ... the possihk exte nt of contam ination of the system by me teo ric wat t l It tlll't hod ex ists thaI
52
RedistribwiOI1 of eiemellfS
depend s o n the measur e me nt of stable isotopes o f oxygen , 11(0 and 16 0 . The ra tio of these isotope s in meteor ic water is lower than it is in marine water ( how much lower is mainly depend en t on the latitude o f th e site o f deposi tion). The measur ed values of oxygen isotope s are ge ne rally express ed by the delta not ation whereb y the ratio is express ed relative to an agreed standa rd (a hdemnite from the Pee Dee Format ion in South Carolin a, USA) .
"'0 =
( 1!II160
u
S.~"1l1c
-
HII60
1111160 standard
) X
1000
~tan
By comparison to today·s rainfall belts, the Solnho fe n meteor ic water o f Jurassic times most probab ly had an isotopi c value o f betwee n -2 and -5 ppt, whilst the original calcium carbon a te which formed in marine waters would have had va lues which were around zero . The graph in fig . 3.1 1 shows the rh;lIlge in 6 1RO of the carbon ate versus strontium co ntent for three o riginal I' pes o f sedime nt : a low-Mg calcite, which is relatively stable , and the unstab le high- Mg calcite and aragonite. As explain ed above. these unstab le compOlle nts ure liable to dissolve and recrystallize during diagenesis produc ing t·arOOn ate pore fluids Ihat are relative ly rich in strontiu m . These pore fluids then migrate ou t of the rock usuall y to be replace d by l1l teoric water with little y Sr and nega tive 6 11(0. Thus. as exchan ge procee ds, stro ntium is remove d from rhe rocks and the extent of the process is also recorded by an increas ingly negat ive oxygen isotope signatu re. The strontiu m conten t of the ftinz ca rbonille was meClsured by Vcizer (1977) CIt about 150 ppm , and an averag e va lue of I)I~O as - 3.5. He explain ed thi s by the diage nesis of a sedime nt contain i ng Aragonit a
10000
"'.
(}OtJlt.
E
•
"
Calci te Low - Mg ca lcite
1000
~
Solnhofe n H;
" ",
"
-, -, -,
-.
9h - Mg calcil.
-, -,
& 180 in CII rbona te
-,
-. -.
Ilg J. II Path of diagencsis for 'Iragoni tic lind cllicitic sedimcnts in contact melcnric w.lter . As uragonitc unci high-Mg c'l1cite recrystallizc to low-Mg calcite wit h undcr the IIlllucncc of mcteoric water. stronllum (Sr) is expelled from the calcium carbonatc I.I1IIce\, rhe CX1Cilt of rccrptal1ll.at ion can be determined from the changi ng oxygen '~IIIIl I)t! vu lucs which hcc(llllc prollr", ivcty lIIore ncgalive (enriched in 16 0) as .hil~c nc ~ l ~ pmcccd ~
Atl:l l)lcd h llm Vc i/cr (11}71)
Petrogmphy of Ihe Solllltofell P/(lII(!lIklllk
about a third low-Mg caleite, which was mai nlyeoceolith pieces . The other two~ thirds could bc ei ther aragonite or high-Mg caleite (or a mixture of both), and probably represents the 'reefal detritus'. In fairn ess, it should be added tha t since this work much more has been learned about the partit ion ing of the elemen t strontium in carbonates and many resea rchers consider diagenetic effects to swamp o riginal differences. Anot her clemen t besides oxygen with isotopes which behave differently during geologica l and biological cycl ing is ca rbon . Carbon is represented by L2C. the most abundant isotope, DC, a rather st able isotope. and J4C, a short -lived radioactive isotope (with which we are not concerned in rocks o f this age) . It is the ratio of LZlL3C in a carbonate which can give crucia l information about its origin . As with oxygen, values of carbon isotopes are expressed by a delta nota tion where they are referred to a standard , usually th at same Cretaceous be lemn ite. LV12C J3112e ) ,DC - ( M'IlIPL" ~I"ndard X 1000 u BII2C slandard In the sea, carbon , in the form of clI rbon dioxide dissolved in the surface waters, is taken up by green plants during photosynthesis, and incorporated into carbohyd rates. The organic matter is eventually broken down, either in the waler column , or in the sediment , to form carbon diox ide agai n. During each of Ihese stages in the carbon cycle, the L2e and De become fractionated ; in photosynthesis plants preferentially incorporate the lighter 12C into orga nic mailer (aL'C org = -27) and the carbon dioxide remain ing in seawate r grows isotopically heavic r as photosynthesis proceeds. When the organic carbon is brokcn down again (a process wh ich in shal low-water environments takes place mainlyon the sed iment surface), the lightcrcarbon is returned to the system, so diluting the heavy ino rganic carbon in the seawater. Mari ne invertebrates bui ld shells by precipitat ing carbon dioxide inlO carbonate and the shells will have 1I 1UDe ratio dependent upon where in the water column they grew and the extent of the carbon cycling processes. An example of the appl ication of carbon isotope measurements comes from forami nife ra in deep-sea cores. Plankton ic foraminifera have ODCc",h around +0 .5. which is often heavie r than the benthic species whose calcareous skeletons have (5 1)Cc"rh of the order of - 0.5, There may al so be a difference in <5 De between species which lived in ope n marine and those which lived in poorly oxygenated environments. An accumulation of degrad ing organic matter will tend to make the inorganic ca rbon in the bottom water. and consequently the (jL)CcHrh signature in the shell s mo rt: negative. Yet, as with all isotope and trace clement studies, diage nesis is 11 complicat ing, and SOme would say ove rwhelm ing, fH ctor Th e ca rbona te recrystallizes and its originnl ODC is changcd, or e l ~c cement' wi th differen t oDe values arc added 10 a rock I1Htk ing the 'whoil- ml.'k ' ()L'C va luc (~f debatable significa nce. Ilowcvcr, carbonat c' wi t h very lI('jI.oI Ilw ,1~ It:ltLLL c, urc
54
Redistribtdioll of elements
.. Ite n those which were buried in an organ ic-rich sed iment. (For a fu ller 111'l"ussion of carbon isotopes, the reader is referred to the SEPM short course hllllk let, edited by Arthur et al. 1983.) (arbon isotope values for the carbonate of the flinz beds o f the Solnhofen l'latlcnkalk are in the range - 1 to +2. Indeed, a block of Solnhofen Platten1...1]1., was used as a standa rd for calibration of mass spectrometers for ca rbon hutupes on account of its pure CaCO] content (see Cra ig 1957). We have tlhtaincd some measurements on flinz and (aute from the Maxberg quarry, !\lIlnhofen (N. J . Shack leton, peTS. comm. 1986). The flinz gave va lues of 18 "I 'c = +2 (6 0 = -3.8) and the adjacent raule was slightly heavier at ,\1 'e = +2.5 (15 180 = - 4.2) . (This cannot be purely a diagenetic effect. orthe Ihlll would be expected to have a more negative oxygen isotope signature than tht· f;iu 1e. However, the detailed geochemistry of this effect would take us hl'~nnd the scope of this book.) These resu lts are exact ly what would be • "pected from a carbonate made of coccolit h pieces . mo ll usc debris, forami niklil . e tc, laid down in a n oxic milieu. They are not commensurate with a n .1l'null ulation o f dead coccolit hophorids at the bottom of an a nox ic wa ter I ulum n (as de Buisonje suggested , see pp . 63-4) because the large amount of III)tllnic matter in the sed iment wou ld yield much more negative results for the hull- ca rbona te. Whether or not these values could be obtained fro m a I uhonate which was precipitated by the activities of be nthic cya nobacteria under hypersaline water column is st ill a n open question , The on ly relevan t '[;lla apparently available for comparison come from recent algal mats o f Solar I IIkc, Si nai . Va lues of 6 13C = +3.5 have been measured in t he carbonate which has been precipitated around cyanobacterial cells (Schidlowski & M.ltLigkeit 1984). H e re the cyanobacterial spheres are on ly fo rming unde r the tit tnceofthe IO
,I
4
Palaeoenvironment and sedimentation
Palaeoenv ironment So regu lar, so tabular, were the sheets oflime mud that became the piaHenkalk that it can only be concluded that Ihey were laid down in very quiet and protected waters. This view has not always prevailed . Ea rly depositional models envisaged the Southern Franconian Alb as a vast mudflat where sedi men t was brought onshore by storms to dry o ut and consolidate under the sun . With this picture in mind , early investigators misidentified the trace fossils as the tracks of walking birds or re ptiles. U nder such a model the process of special preservation was seen as a kind of "mummification ' with corpses lyi ng on the sho re drying out in the sun . Even if th is could have been true for some of the land re ptiles, it is not a n adeq uate explanation (see under biostratinomy of the terrestrial bio ta , p. 93) a nd is a nyway redunda nt in the case of the exceptional preservation of the marine foss ils. The plattenkalk sed iment shows no features to support hypo theses of subae rial exposure. If deposi tion of the plattenkalk had ta ke n place on some kind of mudflat th at was periodically e me rge nt , the n the sedi me ntary seque nce migh t be expected to contain diagnostic sedimentary structures. Feat ures such as channels eroded by tidal curre nts, widespread deposi tion of cross-laminated sedime nt a nd other related sedimen tary struct ures are no ticeably absent. Moreover, in the inte nsely arid climate (see p. 93) the mudfl at would surely have dri ed out, and the re is no evidence for evaporites o r any othe r features of a sabkha-type selling.
The restricted basin model It is now generall y agreed that the pla tten kalk basins lay permanently su bme rged under a stable body of water. However, the basins canno t have been landlocked. There must have been some connection to the sea as most of the fossils are of the bodies of marine organisms, broadly si mil ar to species li ving today in tropical reef environme nts. Part of a coral reef. o f i":'lIc JUrII ssic age, is to be found south of the Solnhofen a rea, now exposed alolltt thl' hanks of the Danube . The Late J urassic cora ls almost certa inly lived, u.. d" 1lI1l~1 modern
56
The restricled basin model
corals, in the well-illuminated surface waters of a shallow sea. That sea must also have been near to the land to rece ive the bodies of land reptiles and insects. r he Solnhofen area may then be thought of, in a broad sense, as a lagoon hordered 10 the north by low-lying land and to the south by a chain o f coral reefs which protected it from the turbulence of the Te thys Ocean (fig. 4.1). The llilse of the lagoon was covered by dome-shaped mounds. built by sponges ilnd cyanobacteria (blue- green algae) in the Kimmeridgian stage of the I.ate Jurassic). The mou nds shielded interven ing hollows from the effects of curre nts and, in the quiet basinal wate rs, the plattenka lk sedim ent was dc posited . There are various ways to estimate the depth of water in the plattenkalk hasins , all relying on different assumptions. Firstly, bX assuming that the
SPOOl"~
mounds
h g. 4. 1 Palaeogeography of the Solnho{en area in Tilhonian limes . The Solnho fen \ hclf wil h its sponge algal mounds and intervening basins was borde red by land to the nort h and e:l~ 1 and . acr01>~ un ooid pl;ltforlll . by thcdcepcrwatersof thcTet hys Ocean in the \(l ulh Red rawn from Meyer in Mcycr& Schrnidl -Kulcr(19tw) .
Palaeoenvironment lind sedimentation
Jurassic coral reds grew in environmen ts similar to today's coral reds, the most active zone of reef growth would have been under about 10 m of water. It also seems plausible that the sponge-algal mounds were shallow-water features, possibly protruding above the surface of the lagoon as islands and separating deeper basins. The relative depth of the basin can then be calcu lated from stratigraphic sections, bearing in mind the relative amounts of co mpaction between sponge-algal mound and bedded limestone facies. Barthel arrived at values for the water depth of 30-60 m. Similarly, the water depth in the basin could be est imated rough ly by knowing the depth of water in which the sponge-algal mounds grew. Another constrai nt on water depth is provided by the cyanobacte ria thought to have formed a mat over the sedimen t surfa ce. Cyanobacteria reflect the blue- green wavelengths of light (hence their alternative name of blue-green algae) whi lst using the red for pho tosynthesis. As the red is the long-wave end of the visible light spectrum th is colour is first to be absorbed when passing through the water col umn . Accordi ngly, it is estimated that in thcse clear, subtropical waters the intensity of red light would be too low fo r efficient photosynthesis below about 60 m (although modern cyanobacteria are known from greater depths!). By constraining the stratigraphic measure ments Keupp obtained the following resu lts: The Solnhofen- Langena ltheim basin is thought to have reached 50-60 m in depth , whilst the Eichstatt basin did not exceed 30 m. T hc Painten basin was also shallow with a maximum depth of 20-30 m, and the Kelhci m basin is calculated to have reached 50 m . STAGNATION OF THE nOT'TOM WATERS In the absence o f ci rcu lation to these isolated hollows, the waters stagnated, developing their own local chemistry which is responsible for the exceptio",.l preservat ion of the Soln hofen fossi ls. The peculiar composit ion of the waters not only deterred normal marine organisms from living in this e nvironment , but for any organism unfortu nate to be washed over the reef and steeped in this solution , death followed very shortly afterwards. Hence the exam plcs of mass mortali ty and sudden death seen in some o f the fossils (see pa laeoecology , pp. 77- 9, and taphonomy , pp. 89-90). Very few of the organisms were still alive by the time they reached the surface of thc sediment and those anima ls which did survivc are well known from other occurrcnces for their tolerance to extreme environment al conditions. For example. the juvenile horse shoe crab, M esofimllills and the crustacean M ecocltirus were still al ive for a short time on the lagoon floor . These creatures produced the famous spiralling trails with the body lying at the centre, interpreted as the last, disorientatcd crawl o f an mnribund animal before it colill pscd in its tracks. Evcn though a few hard .,. 'lll'l'iC' may ha ve survivcd for a shorl time in the lagoon , most a nim!ll ~ \\o{,H' I>.lllnt qUII.: kly arid
58
Chemistry 0/ the Sol/Iho/en wmers
the bod ies fell through the wate r to come to lie o n the sediment surface. Normally corpses lying o n th e seafloor are not left undisturbed because they .lte ut ili zed as a food source by scavenging ani ma ls. They would be d ismemhaed and partially consumed , prod ucing a large surface area for che mica l degradation by microbes and eventua lly resulti ng in the recycling of the o rganic molecules for the growth and construction of ot her o rganisms. But this was no t Ihe case in the Solnhofen environmenL The origin o f the exceptional preservatIon of the Solnhofen fossils is lin ked to the exclusion of macrobenthos from Ihe si te of burial , which ensured that the bodies were not ripped to pieces. I urt hermo re, the inacti vation of a large sectio n o f the no rmal microbial l'\lfllm unity resulted in a very slow rate of decay. Together these factors he lped to ensu re the remarkable preservation of the Solnhofen fossils.
Chemistry of the Solnhofen waters and special preservation HYPERSALINITY? The most convincing explanatio n fo r the poisono us properties o f the stagnant wate rs. that so favoured the exceptio nal prese rvation of the fossils. appears to he an excessive concent ratio n o f sa il. Regrettably, the evidence for hypersalililly continues to be indirect. On pp . 71-3. the evidence for th e climate "ffect ing the Solnhofen area is discussed . Arguments point to hot and dry w nditions, with no indications of any substantial runoff from adjacent landm:lsscs. Unde r such conditions, evaporatio n would be intense and , as the ~!llini t y increased , the dense brine would collect in pools at the bottom o f the IW'IlIls. The brine would have a range of conseque nces fo r the biota and its preservation. Because elevated salinities are fatal to most normal marine nrg:misms. macrobenthos wo uld be excluded from inhabiting the lagoon . !'hese ,mimals SlOp functioning in hypersaline solutions because wate r is withd rawn osmoticall y fro m the tissues. The shrivell ed appearance of ma ny "'iolnhofen jellyfi sh (especially those from the Gungolding-Pfalzpaint area) is qu ite consistent with this idea of hypersalinity. Ano ther consequence o f hypersalinit y is the preservatio n of organic material. ' Pickling' in salt solutio ns 1\ an effecti ve method of culinary preservation, because many of the decompll~11lg microbes arc inactivated and the decay processes greatly slowed . In 11;lt urlll hypersaline environme nts there are documented cases of exceptiona lly \low org:lIl ic decay whk h has resulted in specia l preservation of o rganisms. Fo r ~'·(i111lp l c. in the extreme ly ho t environ ment of Death Valley. Ca lifo rnia, there Me c~ampJcs of cx q ui~itc preservatio n o r insects in the sa lt-rich sedime nt (W. Ucrger. l>cr\. corn m .. 1989). "I he analogy !1elween the ... c.: extre mely salty c.:nvironments and the Solnho fe n lag(xlIlnl ba~i n ~ cl1n not he carried ve ry far. hecause salt concentral ions in the
l~a{aeoeIIVi'OI!",el!l mId sedimcll/mioll
Solnhofen waters never reache d very high values and th e evaporating lagoonal waters must have been constantly diluted by an influx of normal marine water. Certainly the salinity of the lagoonal waters nearly always re ma ined below the level o f saturation with respect to the common dissolved sa lls, as there are no evaporite beds in the plattenkalk sequences. This consideratio n lim its the salinity in the bottom waters to a maximum of 117 ppt , wh ich is the approx imate sali nity at which the first salt, gypsum (CaS04.2 H 20), would sta rt to precipitate. Sometimes the traces of sail crystals, lo ng si nce dissolved away a nd infilled by calcite (ma king salt pseudomorphs) are found on beddi ng planes, but they probab ly did not form on the lagoon fl oor and attest o nl y to loca l cond itions within the sediment. A more revea ling modern analogue to these salini ty-stratified lagoonal basins could perhaps be the Orca basin . Gu lf of Mexico (e .g. Trabant & Presley 1978). T hi s lies in a holl ow in the contine ntal she lf unde r fairl y deep water of a bout 1700 m (and in that it is very dissimilar to the relative shallow plattenkalk basi ns). A layer of brine has formed at the botto m of this depression as a result of the dissolutio n of some of the underlying evapori te deposits. During many centuries organic matte r a nd ot he r terrestrial sediments from the North American contine nt have been washed into the stagnati ng basin. Decaying o rgan ic maile r has totally depleted the brine layer of oxygen. In the anox ic and hypersaline waters , not hing, a pllrt from the microbial community, is able to survive , and without macrobe nthic organisms to bioturba te th e sedime nt , a fine lami nation is preserved. The remains of dead pla nk ton ic o rganism s wh ich fell into the basin. such as the tests of calca reous foraminifera and siliceous radiolaria ns, are exquisitely preserved. The occasio nal fragments of seaweed , which fo und the iT way into the sediment , show remarkable preservation in that the details of cell walls are still visible (Kenne tt & Pe nrose 1978). In the Orca basin a nox icity is the most important fllctor in retarding the rate of decay and promoting exceptio nal preservatio n . Hypersalinit y most like ly has a secondary effect in inhibiting the action of the sulphate-reducing bacte ria which are the first bacte riH to oxidize organic matter under anoxic conditions. This is inferred from measure men ts o f the act ivity of these bacteria which is abnormall y low in comparison with those measure ments from exclusive ly a noxic water such as the Black Sea (Wiesen berg et af. 1979), ANOXIC lTV? AnoxiH has developed in the Orca basi n not me re ly because it has been stagnant for a very lo ng time (carbon 14 calculations g ive a value of 79000 years) , but also because it has a high o rgan ic input a nd is too dee p for any ill sill l oxygen production by pho tosynthesis. Using the O rca ba .. in (I S a broad analogue for the pla tte nkalk basins, we can e xam in e the Vltrll)U S fru; to rs upon which the oxygen conte nt depends. Afte r a slOrm-inthu:l'd l' "dtILt1 /t1.: with the
60
Chemistry of the Solnhofen waters
I d hys Ocean , the water body begins with a ce rtain oxygen concent ration, 1I10st probably a pproaching the maximum amount of dissolved oxygen which may be held in waters of normal marine sa linity (5.4 mVI at salin ity 35 ppt and IX "C, see fig. 4.2). During stagnation the oxygen concentration wil l fallon two .It·counts. Firstly , with degradation of organic matter oxygen is used faster than It r.:; an be produced photosynthetically in the lagoon. Secondly, it will fall slowly .I~ the salini ty of the water rises and is able to hold less oxygen in sol utio n (see l(raph o f salinity vs oxygen concentrat ion , fig. 4.2). If a state of almost total anoxia in the boltom waters has been reached, the terrest riall y derived o rga nic matter is no longer broken down by aerobic microorganisms and accumulates 111 the sedi ment. (The presence of organic matter does not necessarily mean that the bottom waters were anoxic. If a large amoun t of organ ic material is huried in a ra pidly accumulati ng sediment , pore wate rs become anox ic because they have lost contact with the overlying bottom wate rs, even though the latter may still be oxic). T he U ppe r Solnhofen Plattenkalk docs not , in general, have a high proport ion of preserved o rga nic carbon, compared to some o ther Illatten kalks. H uckel (1974b) me ntions a measuremen t of 0.2% Iota I organic \." arbon (T OC) from a flinz bed and 0.9% T Oe fro m a fii ule bed. T his contrasts with an average value o f 1.2% fo r micritic limesto nes (while the very organicrich platten kalk o f Hjoula in Lebano n reaches 2.4%). Certain ly, the underl ylIlg beds ( Lower Solnhofen Pl attenkalk, maim zeta 2a at EichsUitt , and pl atten kalk from the maim epsilo n at Painten) and the overlying beds (M orn, heim beds in the Solnho fen-Eichstatt region) are more o rganic rich . T he Ilrganic matter imparts a brown-black ralherthan a grey-yellow colour to fresh \ urfaces and produces a sulphide smell on fract uring. The absence of preserved organic carbon is most like ly indicative o f a very low fa llo ut of organic material 10 the sediment , in othe r words lagoonal productivity was negligible . U nder these circumstances it is less likely that anoxia would be reached in t he time available before mixi ng and exchange o f the lagoona l waters.
,
_,L - -_ __ I
E
__ _
5
<
~
>
- - __
--- ---- ---
,
~ 1
-
HVposaline
Norma l marine
Hypersa li ne _
~~---o,~o----C,"o----C'"OC-'--."OC---~,oc---~,oo---~,~o----~,o Salinily 1%.)
hg. 4.2
Oxygen cQnccrm:lrion in walers of varying salinity demonstrating how. with
l m;rCn\lng sI11inil),.
oxygen ,(Jlubi!ll ), decreases . From Caq>enter (1966) .
Pa/aeocll1 1irOllmel1l1llld se(/ill/elltation
Other argumcnts for a general oxicity of the plattcnka lk waters have also been presented. Yeizer (1977) measured the iron and manganese contents of calcium carbona te from the plattenkalk flinz beds and compared his results with those from other south Ge rman Jurassic deposits. The elements Fe and Mn were introduced into the plattenkalk sediment , bound inside the lattices of clay and oxide minerals. iron predominantly in the valency state III and manganese in IV. Under reducing condit ions these elements gai n electrons from other atoms and acquire a valency state of II. Fe 2 + and Mn2+ are water-soluble ions and move out of their origi nal minerals into solution. Accordingly. calcite which precipi tated from anoxic waters would incorporate 11 relati vely high cont ent o f soluble Fe and Mn, in relation to a calcite prccipitflted frolf' oxic wate rs. Yeizer obtained average values of 100 ppm Fe and 70 ppm Mn for thc conccn tnH ions of these elements in the fli nz carbonate. Thcse results arc consistent with vil lucs obtained fro m carbonates wh ich formed in normal marine rather than those from anoxic env ironments. However. given the probable mode o f dcposition of these carbonates the resul ts arc perhaps not very surprisi ng. If (as described on pp. 65-7), the flin z beds are made out of carbonate formed in normal marine environments, deposited rapidly and lithified early , then they shou ld show a normal marine signature. To test if the bottom wate rs were anoxic the Fe and Mn contents of the well preserved foram inifera (which presumably suffered very little diagenetic exchange) should be measured. As the foraminifera almost certainly lived in the lagoon we might then havc a sounder basis for comment on the oxicity of the lagoonal waters. The two other arguments generally cited in favour of low oxygen concentration in the plattenkalk waters we find similarly inconclusive. Firstly, there is th e argument based o n pyrite. Pyrite (FeS2) forms under anoxic waters or in anoxic sediments. The su lph ide ion is supplied by the bacterial reduction of sulphate, which is derived mainly from seawa ter and the Fe 2 + from the reduction of Fe(lII) minerals. Pyrite is not a common constituent of the Solnhofen PllIltenkalk . although some finely disseminated pyrite does cause a bl ue-green tinge to some of the Solnhofen lithographic stones. But in compnrison wi th known anoxic deposits it is noticeably lacking. There arc a number o f possible explanations to account for the absence of pyrite, some of which ca n be dismissed. The suggest ion that pyrite fo rmed but has since bee n redissolved is addressed by Keupp ( 1977a, b). He argues that this is not the case, because there are no 'etching' struct ures on the ca lcite particles which would be made by an acidic solution which dissolved the pyrite. An explanat ion for the 1I0nforma tion of iron sulphides cou ld be in the inactivity o f sulphatc-reduci ng bacteria because they arc inhibited in the salt y watc rs or because the water... were not anox ic and ot her bacte ria preferentially reduced the organic matter. One of man y ot her explanations is a deficiency of iron. hC(;lH''>C the ... upply o f iron-containing minerals was too low .
62
Chemistry of tile Soll/llofel/ waters
A fina l argument advanced concerning the ox icity of the bottom waters is !lased upon the preservation of the siphunc1e of ammonites. The siphuncular lube is a paper-thin , weak ly phosphatic structure which runs inside the margin Illt he ammon ite shell to the initial chambe r from wh ich the animal commenced )!nlwth. In black shales deposited under anoxic conditions, although the spt.!cimens are crushed, the siphuncle is preserved as a distinct dark-coloured IlIIe. Siphunc1e preservation is normal for ammonites in the Mornsheim beds uve rlyi ng the Solnhofen Plattenka lk but , according to Keupp (1977a, b), the siphuncle in the plattenkalk ammonites is not preserved and this is evide nce iI!!a inst widespread bottom water anoxicity. Others, notably O. Viohl o f the Jura-Museum, Eichstiitt , would disagree with this statement of Keupp 's, d;lIming that siphunc1e preservation in the platten kalk ammonites is not unw mmon and making redundant this argument for plattenkalk waterox icity. In all probability, oxygen concen trations varied from normal marine to ulmost anox ic, this depe nding upo n th e period o f salin ity strati fication and the Icsultant degree of stagnation. OTHER POSSIBILITLES? A different explanation of the hostile conditions prevalent in the lagoona l wlltcrs was put forward by Paul de Buisonje of Amsterdam (1972, 1985). de Jiuisonje proposed thaI an upwelling curren t (presumably off the shelf edge) produced seasonal blooms of coccolithophorids in the lagoonal waters. As I he~c microorgan isms died and fell through the water column , toxi ns produced In the decay of their bodies soo n poisoned the bottom waters . Upwell ing mixed tll l\ pu trid water throughou tlheentire lagoon e nsuring an environment hostile ttl any marine macroorgani sms which the currents had swept into the area. I heir corpses sank to the bottom to be buried by a rain of coccoliths from the nvcrlying waters. de Buisonje's speculations are based on what appear to be vcry insecure I'lcmises. The original idea that the plattenkalk 'lagoon' was subject to an upwelling current is clearly based on the superficial similarity between pa laeot\~'og r
n3
Palaeoenvjroflmem wid se(lime/l/OIiQII
productivity in thesurf,lce waters of the lagoon , a consequence of the upwelli ng current. Where then are the numbers of nek tonic macroorga nisms which fed off this plankto n and which we would expect to be e mbedded in the sedime nt , particularly the faule sed ime nt ? The scarcity of fossils from the Solnhofe n limestone indic.ltes the essential ste rility of the lagoon . As present-day coccolithophorids have never been shown to produce measurable quantities of toxins in their decay, the re seems to be no reason to suppose that the decaying coccolithophorids in the Solnhofen lagoon would poison the water. de Suison je then suggested th.1I other plnnkton which bloomed with the coccoliths, such as the dinoflagellates, were the toxin producers, but that they were not preserved , which makes this idea difftcult to test further. In addit ion, a nd perhaps most concl usively , the very low concentration of organic matter in the plattenka lk also indicates that the lagoon was an a rea of low productivity.
Blooms of microorganisms As hype rsalinity neve r ach ieved the high values leadi ng to the precipitation of evaporites, the stagnation can only have been te mporary. The water column mixed and exchanged with the open sea, diluting t he overa ll sa lini ty and refreshing the lagoonal waters. Immediately ,Ifte r these episodes , cond itio ns were sufficienlly equitable, especially with regard to oxygen, to allow ccrtain opportun istic species of microorganisms, mai nly benthic fo ramin ifera and coccolithophorids , to completc their sho n life cycles in the lagoon. The prot ists ma tured a nd reprod uced before the salini ty became too high fo r their continued survival, and t he ir tests collected on the surface of the sediment. D uring format ion of these microfossil laminae (th in intercalations between ftinz beds and in raule interbeds) the salini ty must have been less than 60 ppt (c. Hem leben, pers. com m. 1986) even a t the bottom o f the lagoon to pe rmit foram iniferal growth , a nd yet must have been sufficie ntly high so that macrobe nthos did not enter the lagoon and biot urbate the sediment. Sa lin it ies of 4050 ppt would be quite sufficie nt to deter most animal and plant species ( He nt1eben 1977) and both the assemblages of coccol iths a nd foramin ifera a rc consistent with the idea of weak hypersali ni ty throughout the water column at these times (see palaeoecology. pp . 73-4).
The cyanobacterial mat The fiiu le and possibly to a lesser e xtent the flinz have yielded the coccoid spheres thought to be the remai ns of cyanobacte ria (see PI' . 45-7). and their occurrence fi ts well into the environme nta l reconstruct ion l)i) fllr presented. Al) salinities increased 10 leve ls which the protists could no t wlcrnlC. U IlI' oj the few
64
A dl'posiliolla/ model
.Irgan isms left to inhabit the ot herwise steri le environment were the cyanobaclai a. Cya nobacteria still flouri sh under very salty water , forming a mat o n the ,urface of the sediment which is not disrupted by burrowing organisms. ( 'unsolidated by the slime produced by the cyanobacteria, the mat surface is lurther hardened to a thin surface crust by the calcium carbonate which preci pitates around the cells as a by-product of respiration. rhis enveloping of the limy sediment by the cya nobacteria l mat resulted in a m hesive texture to the surface of the sediment (rather than the ' soupy' texture ~ hich is found in lime muds of modern carbonate environments), ideal to take up the delica te traces made by the Solnhofen organ isms. A cyanobacteria l mat which grows over corpses lying on the sediment surface, encapsu lati ng them in .1 fi lm of calcium ca rbonate, could help to explain Ihe unusual nature of the IIn!servation. Modern cyanobacterial mats will grow over entire corpses within huurs or at most days (D. Herm, Munich. cited by Keupp 19TIa). An Impression of the body is taken up into this thin calcareous mould before IIlIernal decay sets in and the corpse falls apart. With in the strongly reducing \' nvironment crea ted inside this calcareous envelope , the soft tissue decays \'xlre mely slowly lind the body resists the pressure of the surrounding sed iment Inr a relatively long time. When the body finally collapses. the surrounding \ediment is already quite well consolidated and this gives rise to the charaete ri\lic pedesta l preservation of the Solnhofen soft-bodied fossi ls (see fossil diagenesis, pp. 96-9). Preservation o f the fossils by the cya nobacterial mal 'l'cms entirely plausible, bu t if Barthe l's deposiliona l theory is followed rI/o:\lrously there is not time for growth of a cyanobacterial mat before the \edime nt (which arrived in the lagoon in the same current of water) settled over the corpses. It seems that a cyanobacterial mat may well have been present in Ihi" type o f environmen t (and see latc r under deposit ion) but it is not necessari ly responsible for the preservation o f the fossils.
A depositional model I he general consensus, promoted by Barthel, regarded the plattenka lk sedime nt as a ca rbonate ooze which had accum ulated around the coral reefs (fig. ·1 1). I>eriodically, storms stirred up this sediment (rom the seafloor and it heeame suspended in the turbulent water (fi g. 4.3b). The sediment-laden water \\ ;li-hcd over the coral patch reefs and fl ooded into the lagoon , the coa rse r lr"aclioll of the sedi ment , the 'reefal debris' , being dropped after a short ,h\ tance, whilst only the finest particles were transponed the long distance 10 the Solnhofen area . Some reefal organ isms were a lso drawn into the lagoonal waters. Their bodies sank to the lagoon floor to be covered by the more slowly 'C lIllllg, fi ner sed iment (fi~ . 4.3c) . Thh '" u~pen,io n Ihenry' of \cd illlent transport was firs t propou nded by the
Pulaeoe"virOlllllelll and sedimellllltiotl
Soulh
NOIlh
SEA
---
FAULE
Sallnlly-"rlllflcatiOtl wilh hyp ..... lln. bollom ...11 ..... Slow but con tinual doIrpo.lllon 01 I.r>d-d.lved ell,.
a
.c;:--.....:.. ,
REEF
"' ~---
Umlted pch,n!!" 01
IIIgoon,' ....1.' wil h open .... Some Ii ... _bon,I, brought In .
l"gill,,,IKI'" mlc.We llmel'
"
------Mlnne carbon.l. 00...
.
", -------_. ~ e- "'~)"-: brlnglllll 11m. mud '.om ..ound tI., 'HI .
Storm.... uh .,.... Ih. . . ., ",,"m,I, ••• """,Ined In 1M Ilow.
b
c
to
~
,,_.d try
,~",..,t. 51'11",,101' . ......... with .. ~ni IV -""l l f lclllon.
Fig. 4.3 Barthel's theory of deposition of the Solnhofen Plallcnkalk . The carbonate in both ninz and faule is regarded as allochthonous and of shallow marine origin.
Dutch sedimentologist van Stntatcn ( 1971). De position out of suspension explains how the particles rained down vertically upon the dead organ isms and shells. The different pulses of scdimCnI each formed a lamina draping around the fossil. This is an unusua l phcnomenon: us ually potential fo\\i! .. are buried by a unidirCCl ionlll . sediment -Iadcn curre nt which will , nlOolh lhe ..cdimcnt surface over the si te of burill I. In contrast . the depOSitIOn of Ih l' 111;lth:nkalk W:I!o ;{,
Other depositional theories
Ilot accompa ni ed by currents over the basin floor. In the Soln hofen-EichsUitt ,t rea this is clcarly shown by the saucer-shaped Inoceramus and Os/rea shells dnd ammon ite aptychi. 90% of which lie convex down, in an o rientat ion unstable in currents. Some bulbous ammonite she lls such as Aspidoceras and the occasiona l belemnite are embedded vertically in the sediment and this is the position in which they would first have settled. Other indications of very quiet wa ter are the resting impressions found adjacent to the body fossi ls formed as the sin king animal touched down. The blanket cove r of fine sediment also provides an explanation fo r the correlation of beds for many kilometres within somc basins (correlation of Oinz beds between dilTerent basins being a little more problematic). Barthel saw no essential difference between deposition of flin z and mule. rhe ftinz was a concentrated deposit brought into the lagoon by the stronger .. torms, whi lst the faule ca rbonate drifted in on gentle curren ts (too weak to l.'n lrain animal bodics), accumulating slowly over a long period of lime and diluted by land-derived clay (fig. 4.3a). The now well-preserved coccoliths and hent hic foraminifera , which (accordi ng to Barthel) form only a small pe rcentage of the fiiule carbonate. grew in the lagoon at times when the lagoonal wilters (wh ich were never in complete isolation from the sea) were of lowest ..alin ity. Barthel also suggested tha t the foraminifera might have grown on the .. ides of the sponge-algal mou nds and been washed into the more hype rsali ne depths . The time taken to deposit a ftin zlfiiule cou plet can be estimated o nly l'x lrcmely rough ly and by the following calculations: the amount of ammo nite l.'vtJlution between the top and bottom of the Solnhofen Plattenkalk is equivall'll! to about half an ammonite zone and, in Upper Ju rassic rocks, o ne ill11monite zone must last for on average a million years (given the number of ,I tllmonite zones and the tota l time to deposit the Upper Jurassic rocks as ,,, Iculated from radiomctric datcs). Therefore, the Sol nhofen Platte nk alk (U pper + Lower) may have taken around 500 000 years to be deposited. In this lillie some 500-2500 fl inzlfiiule couplets were formed (as calcu latcd by the ilvt::rage th ick ness of the beds and max imum thickness of Ihe seq uence), so 111:11, on average, each ftinz + faule cycle took of I he o rder of 200-1 (X)() yea rs to Ill.' deposited.
Other depositional theories Wh i]<,t accepting thai th c tl in z sediment was allochthonous (i.e , brought in to Ihe klgoon), ra th er th.1n autochthonous (formed in the lagoon). Adolf Se i11II.:hcr (Seilaeher 1963, Gold ring & SeiJache r 197 1) thought that the fl inz beds WC IC the end products of turbid nows of lime Ill ud down th e sides o f the ~ponge- al!\allllo\l n d .. , I hi" I" alrno .. \ certainly the elIse for other pl
67
/)a/aeoenvironmelll and sedimelllalioll
rmmy of which show clear evide nce in the form of grading, basal gouge and scou r marks and beds of limited areal exte nt. However, most other authors reject the suggestion that the plattenkalk beds are turbidites on the fo llowing grounds. If the individual plattenkalk beds have been correctly correlated between outcrops and a re thus single episodes of deposition , then it seems difficult to see how a si ngle turbidity current cou ld be responsible. give n the highly irregu lar topography of the lagoon floor. It is certainly true that some o f the plattenka lk beds are graded. but deposition of any suspended sedime nt can produce this. There are also a few examples of ammonite roll marks from the Solnhofen-Eichstatt area. According to Seilacher these must have been produced by ammonites being bowled along the surface in a st rong, sedime ntladen fl ow, and are inexplicable in a gentle energy regime. But , according to Viohl (pers. comm . 1986), the rollmarks cited by Seilache r a re not from the Solnhofen Platte nkal k at all , but from the Mornsheim beds, which were deposi ted unde r quite different condi tions. Nevertheless, some beds in the Painte n a rea are definitel y turbidi tes. These obviously graded beds, whe re ammon ite rollmarks and other scratch marks are common , wedge out over dista nces of tens of metres. It is also quite li kely that some o f the flin z beds from Solnhofen itself may have thickened by slippage of sedimen t down the sides o f the sponge-a lga l mounds. Another varia nt on Barthel's deposit ional theory was provided by He mleben ( 1977), who also conside red the flinz to be a n allochthonous marine ooze. but thought th at the bulk of the fiiul e carbonate was autochthonous a nd made of lagoonally produced coccoliths and benthic foraminifera . In postulating that during interva ls of fau le accumulation, biological production in the I'lgoon ex te nded from the surface righ t down to the lagoon floor . He mlebe n the n had to dispense with the idea of hype rsalinity as the supposed explanation for excl usion of macrobenthos. As a substitute he suggested that the sediment texture was too soupy for macroben thic colon ization , but this does not explain the rarit y of macropelagic fossils in the faule. Based on his own observations and recognition o f cyanobacterial sphe res in the fau le a nd ftin z (see pp . 44-8), Keupp's ( 1977a, b) depositional model is ingenious a nd fundamentally di fferent to Barthel 's. U nder Keupp's theory the flinz was produced o n the lagoon fl oor unde r stagnant , salty wate r of varying oxicity by the uninterrupted activities o f cyanobacteria (see fig. 4.4). From time to time the surface waters would be mixed by turbulence and would excha nge wit h normal seawate r, so refreshing the upper layers of the lagoon . During these brief periods coccolithophorids were a ble to grow in the upper wate rs. On death they fcll to thc lagoon floor a nd now constilUte the distinct white coccolith laminae in the flin z. Clayey bedding planes formed whe n the e ntire w:ller column mixed . kill ing the cyanobacteria l mal. temporarily halting the CHrbo na te production and resulting in a relatively hi ghcr clny eunte nt for the lamina (there is continual backgrou nd dcposition o f II Illa r III\! duy) . The wa ters
r••
Other depositional theories
So.",
N'>I' lh
seA
1.0.1<1 0
,U I EVAPORAnON ~~-
I
Sallnltv - .I<.liIic.lion wi l n hYP"'..lin • • ,lgn.nl bottom Wll ..... &lnthic cv-nobacl.rl, produc. lime-mud.
b
FLlNZ lpu.. micritic Ilm..lonai REEF
-------
SIOfm. l.ad \0 miKing 01 lagoon.' WII" column; .ome animal. Ind ",•• Ine cI.y Iiso .wepl In from open .... M... "'Oftelity.
1·lg. 4.4 Keupp's theory of deposition of the Solnhofen Platten kalk. The ft inz and 'om..: of the filule carbonate is autochthonous and precipitated due to the activities of "y;ll1obacteria which grew 011 the lagoon floor. Fiiule is formed by a repeated mixing of the cntire lagoonal water column. The lowe r calcium carbonate production by the "yanobacteri:1 over this period is responsible for the relatively higher clay content of the hcd . CY:l1lohaeleria I)roduec calcium C
1)(lla~oenvirol/lntll/
and sedin/ell/mio!!
mi xed and exchanged with the open sea, bringing into the lagoon a sparse macrobiot a, which was predominantly nektonic. Most of these anima ls were killed on con tact with the salty water and thcir bodies came to lie in the thin ShOlly lamina. With furtherwatcrexchangc planktonic coccolithophorids began to inhabit the surface waters together with the nektonic animals which fed off them which produced the coprolitic pellets. With the return of stagnati on the forami nifera wcrc unable to survive and the lagoon Hoor was again taken over by the cyanobactcria. For Kcupp, the fiiu le consists of a stack of closely spaced clayey coccolithl foram inife ral laminae intercalated between thin cyanobacterial laminae (see fig. 3.8, p. 48). Thus faule production rcpresents repeatcd eve nts of holomixis (mixing of the ent ire wa ter COlumn) be tween briefer periods of stagnation. The cyanobacterial lamin ae which make up the bu lk of the Hinz
7()
5
Palaeoecology
Palaeoclimate Palaeogeographic reconstruct io ns fo r the Lale Jurassic world show sout he rn Germany and so the Soln hofen district to be somewhere between latitudes 25° and 30" N. In this lat itudi nal belt , albeit o n a globe with somewhat different distribution of continental masses, we can infer that the Solnhofen area would have lai n in the subtropical, semi-arid zone. This region would have been ~ ubjccted
to seasonally wet winters and prolonged dry summers, but as
moun tain ra nges were absent in the region, overall there wou ld have been litt le
rain. The general indications are o f a warm , but desiccated clim ate. The first line of evide nce for this comes fro m the gene ral sedime ntology. Limestones are the predom inant lithology o f the Upper Jurassic strat a of southe rn Germany, and ;llthough carbonates can form under cold climates , they predominate in warm waters where there is a wea lth of calca reous she ll-form ing o rgan isms. T he Solnhofen carbonate is also unpoll uted by te rrest rial sedime nt , so it seems un likely that major rivers washed off the land into the lagoon. In turn , this \ uggests a lack of rainfa ll a nd an arid climate. The types of a nimals a nd plants prese nt also support this conclusion. In the subtropica l climate coral reefs flo urished in the Southe rn Franconian Alb. The corals in these Jurassic reefs may not be identical to today's forms, but they a re sufficient ly simi lar for us to \U Ppose that they lived in clear . warm water, probably in the range of 20-30 0c, 1\ te mpe rature value of 26 DC for surface water tempe rature was obtai ned by ,lila lyses of the oxyge n isoto pes in two calcitic belemn ite guards ( Engst 1961). I his method of palaeotemperature calcul atio n relies o n the observation that '.lI io of different isotopes of oxygen 180 and 160 incorporated into calcite depends on the te mpera ture of the seawater in which it form s as well as its I.llilude, sa lini ty and several o ther com plicating factors. The value for wate r te mperature is calculated using the Epstein formu la:
'IrC) ~ 16,9 - 4,2(0, - 0.) + 0, 13(0, - 0.)' where: I)c = b 180 of CO 2 generated fro m carbonate at 25 DC (relative to a belem nite frolll the Pee Dee formation in South Caroli na, USA) ()w - bll~O o f CO 2 generated in eq uilibrium with waler at 25 DC (relative to Standard Mean Ocean Water (S MOW» From Epstein eI al . 1953
P(llaeoecology
The temperature on land would have been higher st ill, and intense evaporation exceeded the small amoun t of precipitation. The plants now fossilized in the Solnhofen Plattenkalk exhibit various adaptations that seem to reflect the need to cope with water shortage (e.g. Meyer 1974). The seed fern Cycadopteris reduced evaporative water loss by a thick leathery cuticle which covered the upper surface of t he leaf and also overhung the sides as rims. Moreover, the stomata of the plant which were restricted to the underside of the leaf occupied sunken pi ts. The con ife rs Brachyphyllllll1 and Palaeocyparis had tough cut icles and minim ized the exposed surface area by adopting scale-like leaves. These plants were strengthened by a central rod of wood, surrounded by an outer cylinder of spongy pith tissue (now calcified) in which the plants could store a certai n amount of water (l ung 1974b). Simi lar structures arc found in the presen t-day cact us where the pit h cavity is an adaptation to a dry climate. Anot her incidental consequence of t his construction is that the con ifer stems cou ld never have grown to any substantial height (less than 3 m) because of the relative weak ness of the slender stems. Weathering of land under a hot, d ry climate yields characteristic products. In the chemical weatheri ng of si licate-con tai ning rocks to clay minerals, the proportio n of t he clay kaolinite relative to montmori llonite and ill ite can be influenced by climate. Genera lly kaolin ite forms in more acidic mi lieu and pa rticularly in hot and humid conditions, but it is important to rea lize that many other factors also control clay mineral distribu tion. In practice, so much depends on the composition of t he parent rock and the chem iSlry of the depositional environment th at the palaeocli mate was probably of secondary importance. In the Solnhofen Pl atten kalk, there is a low but va riable amou nt of kaolin ite wit h respect to illite and mont mori llonite (e.g. Huck el 1974a) and considerabl y less than in the beds eit her immediately above or below. T he Solnhofen Plattenka lk is also anomalous in the complete disappea rance o f illite in favou r of mixed layer mi nerals. All thi s seems to suggest that t he plattenkalk's deposi tional environment was unusua l, but in what respect, the clay minerals do not easily tell us. The fi ne clay fraction in the plattenkalk sed iment was probably ca rried in to the lagoon by wi nd rather t ha n water. The few quartz grai ns show clea r evidence of aeolian transport in that when examined under the elect ron microscope they are spherical and have frosted surfaces. Although this does not necessarily exclude a fina l period of water-borne transport into the lagoon, there is no direct evidence fo r the presence of major rivers emptying into the lagoon. Neither chan nels nor associated sed imen tary structures typical o f fluvial environments are found and the lagoon was essentially starved o r terrige nous sedi ment. However, the few bodies of land animals and pllmts must have been transported somehow into the lagoonal sediments and,
Life in 'he lagoon
spasmodica lly, rivers must have drained the land surface. Freshwater ponds must also have existed seasonally on the land to provide a home for the larva l stages of the Solnhofen insects .
Lire in the lagoon Between the low-lying land to the north and {he southern coral reefs , the lagoon itself presented a range of environments potentially open to colo nization. Mounds, made from sponges and cyanobacteria (now dead) and their trapped sediment , protruded from the lagoon floor , leaving depressions where the plattenkalk sediments accumulated. The irregu lar topography formed by the dend sponge~a l gal and coral-encrusted mounds would have helped to limit the strength of water currents. As the water stagnated, evaporation produced a salin ity stratification through the water column with denser, hypersaline (and o nly weakly oxic , see pp. 60-3) water at the bottom of the basins. The de n sity~ ~ alin i ty stratificat ion was very stable. Weak water curren ts failed to remove t he stagll
Palaeoecology
species and consists almost entirely of smooth, unornamented forms (Groiss 1967). This is clearly indicative of hostile conditions which only a few forms could tolerate . Groiss (cited in Viohl 1985) also asserted that the foramin iferal abundance and diversity decreased from Eichshitt towards Solnhofen and Langenaltheim , and this may be in a direction of increasi ng water depth and more permanent sali nity strat ification. Ostracods from Langenaltheim , studied by Gocht (1973), were not preserved in sufficient detail to allow them to be identified even to the level of gen us so, despite their general utility in palaeoenvironmental reconstructions, they cannot help in any discussion as to the sali nity. But the ostracods were not immune to the hosti le environment and their death seems to have been sudden. Thus, they are preserved in life position with the bivalved shells vertically embedded in the sediment before they were subsequently squashed during sediment compaction. Accompanying the foram inifera and occasional ostracods o n these clayey surfaces are a scattering of coccoliths, the remains of coccoli thophorids which would have lived in the surface waters of the lagoon. Some lam inae conta in quite diverse assemblages which may reflect normal marine conditions. O the rs are ve ry poor, with a predominance o f one species, Cycl(jgelosphaera margereli, which was presumably toleran t to conditions of increased salinity (Keupp 1978). Some coccoliths are preserved in in tact coccospheres wh ich would normally disaggregate only hours after the death of the algal cell which made them and so can only have been transported a short distance to their site of burial. One way to remove coccoliths rapidly from the surface into the conserving mil ieu of the bottom waters is inside the faeces of macroorgan isms, as seems 10 have been the case for some of the fau le coccol iths. Some macroorganisms may have existed for short times in the lagoonal waters. In particul ar, the small crinoid Saccocoma, which is found in large numbers at the base of some fl inz beds, flouris hed on favourable occasions in the upper waters of the lagoon. Plates o f Saccocoma can also be ident ified inside specimens of the worm-like faeces , known as Lumbricaria illleslinum (Janicke 1970a). Lumbricar;a is a contorted, worm-like tube with a circular cross-section (diameter 1-4 mm) and a length that may reach 170 em (fig. 5.1). The foss il is made al most completely of ca lcite, mostly recrystallized but occasionally still showing the net-like ret iculate fabric typical of ech inoderm plates. Lllmbricaria is one of the most common fossils in the Sol nhofen limestone, and we might reasonably expect it to have been made by an organism represented in the commonest groups of body fossils , such as the fish , crustaceans or cephalopods. Squids and cuHlefish turn out to be the best candidates, because there arc close comparisons between Lllmbr;caria and the faeces o f the modern octopus (Janicke 1970a). The diet of these cephalopods must have incl uded large numbers of SaCCQcoma, and the indigestible skelc t:ll plates passed out in the faeces. Alt hough the plates were probably bound IOgether by mucus, the shape of Lllmbricaria look!> very much 1I~ if it fell
74
Life ill 'he lagoon
". , .,
-.-~""...,..,
'.
'.
, "
',.
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I·
I..
"
,
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':
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Itg. 5. 1 Trace fossil ; Llllllbricaria ;lIIeslimmr GoJdfuss, Schcrnfeld bei Eichsliilt; nla.~i mum
diameler of fossi l 102 mm ; BSPHGM 1964 XXIII 161.
direct ly from an o rga nism wh ich li ved in the l.. goon rathe r than being b ro ught III fro m elsewhere . A rarer type of LumbriclIrill. referred to as a separate trace fossil species, L. r('clll. probably has a different o rigin . L. reCf(l is an e longate worm-like trace ~h()rte r than thc marc COOlmon form , generally straight or sligh tly curved and l'rc~c rved wholl y or part ly in a phosphatic materi aL sometimes accompanied \1y ~'llcite (fig. 5.2). The phosphatic preservation suggests the coprolite con"'Icd mainly of fish fragment s with a secondary echinoderm compone nt. The Iragmcnl s which it contai ns are relatively large and presumably incompletely du.:wed . T his, together with its short length . suggests its mak er was prob'lbl y a li~ h . Cough balls (Jan icke 1970b) are anot her type of ejecta, but spat o ut o f the nlnul h of an animal. An elliptical ball. 12.5 by 15 em, which contained the ,cnn:cly chewed or digested rcmnants of a 45-50 em long fish is shown in fig. ~ .1, The di,ta'tcfu l morscll1lu
Palae(Xcology
Fig. 5.2 Trace fossil ; LWllbriCM;(I rec/(I Goldfuss, Langenaltheim; maximum width of specimen 145 mm; collection. preparation and photograph Captain G . Brasse1, Flensburg-Milrwik.
Very occasionally the Solnhofen fossils show signs of predation. Examples are crunched ammonite shells o r ha lf-eate n fi shes wi thout signs of decay ( Mayr 1967). The surface waters also carried the planktonic larvae of macroorgan isms. in part icular, bivalves. Some bivalve larvae found rel
Life in the lagooll
-------
-----~
) \
- -- ---
Fig. 5.3
--
-
Regurgitated Calums (Strobilodlls) sp .. Blumenberg bei Eichstatt; maximum
di,l rnetcr 157 mm ; BSPHGM 1964 XXI II 111. basins the severe trauma was overwhelming and led to rapid death , p robab ly hefore they reached the sedime nt surface. The sudden death of the o rganisms can be seen in some of the ot her fossil specimens. Some fis h had evidentl y just had the benefi t of a meal as recently eatcn prey can still be seen in their , tomachs. Even more astonishi ng are those fish with prey sti ll in thei r mo ut hs. rhe~c creatures evidently made a last snatch at a dyi ng fi sh before they thcmselves perished (t hey also could have died from choking). A ve ry few, relatively tole rant anima ls were able to survive the hypersa line rnlhcu for n short time. pcrllaP' II mailer afhou rs. but all theirtraecs e nd in the
77
Palaeoecology
Fig. 5.4 TIle brown alga, Phyl/Ollw/{lis Ia/ilmlls Rothplclz encrusted by oysters, Haunsfeld bei M
Fig. 5,5 Xipho~unm chcliceratc; Meso/imll/lls walc/ri Dcsrnnrc\,t 'U\{t II~ 'plral'death ' track, MlIxherg bei Solnhofen; carapace width 92 01111, MSAV
Reefal commullities
Ik ath of the beast. Washed into the stagnant , salty basin , they were merely able 10 crawl in a disorie nted spiral before collapsing in their tracks. Most fa mous and comparatively common are the tracks of t he horse-shoe crab , Meso/imllllls (Iigs. 5.5, 5.6 & 5.7). The individua ls which crawled and d ied on the plattenkalk "'l:diment in the Soln h ofen~Eichstatt area are all juveniles. More normal life .It:tivities of the larger mature limuJids are found near to Painten . where the water was better mixed and compara tively more hospitable. In modern fi ll/lllllS , juven iles , unlike adults , swim upwards when disturbed and so were probably more susceptible to being washed away. Of the juveniles' t racks Icco rded in the Solnhofen Plattenka lk one type of trace starts as the an ima l, which swims on its back (as do modern limulids) , lands , tu rns itself ove r, and Ihen goes for a short meande ri ng wa lk (Fisher 1975a). The othe r type of trace is Ihcspiral death track with the body at the end. It has been suggested that t hese Il' presented moulting act ivity but this ca nnot be the case as there arc no marks nlllde by the an imal aft er it had crawled out o f its skin. Some of the longest of till: spiral tracks were made by the biva lve Solell/yo , a genus well known for its I; nvironmen tal to lera nce. Its muscu lar foot excavated a deep furrow in the ...eliimc nt, the two edges of the gaping shell carving the outer furrows (fi gs. 5.8 ,'
Reefal communities It is main ly the bod ies of mari ne rat her than terrestrial organisms which were trn nsported into the platten kalk basins and became foss ilized. Some of t hese may have lived around the tops of t he spo n ge~a l ga l mounds which penet rated the less salty waters of the lagoon. Others must have come from comm un ities 11 11 the periphery of the lagoon , e ither sponge-dominated mounds or else ' 1 'H. lIl ge~a l ga l mounds overgrown by corals (see also st ratigraphy , Pl'. 24-37). When the storms washed the organisms from these areas, some organ isms were lIlore likely to be carried away than ot hers (see taphonomy , next chapter). T his hia... in thl: types of an ima ls represented in collections must be borne in mind whcn piccing together the compone nts of this Late J urassic ecosystem. Whilst sponges grew in thicke ts, trapping sedime nt between them and Im ming gently rolling mounds. [he co r.. ls built a strong , steep fram ework. SU IIIC I) f th c.,e organism... , ~uch a, the cal careous bryozoans and (questionabl e) 79
Palaeoecology
Reefal commlllli/ies
,
, ,'
"
, Fig. 5.8 Biva lved mollusc; Solemya sp., Eichsliittj cast of an original destroyed in the war from BSPHGM; bivalve 10 mm long; J ME .
Fig. 5.6 (inset opposi te) Xiphosuran cheliccralc; moult of modern Linlll/lis /loly(Linne) , Florida: length 141 mill; private collection.
p'lf'mll.~
hg. 'i .7 (oppmilc) Xiph,)~ur;1I1 chdicCTUIC ; Meso/illlllilis w(llchi DcsmarCSI and walkllig track. Solnhofen , wIdth ,)1 truel., lit UPllCl'lllmt part of platc 105 111m; MSA V .
Palaeo«ology
Fig. 5.9 Bivalved mollusc; Solemya sp. , Eichstall; cast of an original destroyed in the war from BS PH GM; bivalve 12 mm long; JME.
soft -bodied gorgonians (a group of cnidarians that are related 10 other corals) have been preserved, bUI there were almost certa in ly other soft-bodie d coelenterates and many algae of which there are now no trace. The bulk of the reef frame was made of corals and encrusted by other coni Is. coral-like hydrozoans and calcareous algae, all adding to its strength . Inside cracks and crevices lodged brachiopods, attached by pcdicles , as well as various bivalves that included clusters o f mussels hangi ng by byssal threads to the substrate and oysters cemen ted onto the rock . The calcium carbonate reefal structure broke up under the action of the waves into blocks of debris and finer sediment. Many organisms sought anchorage in the sediment. Th ese included bivalves such as the triangular Pilllla . and some holothurians, wh ieh by ana logy with modern genera lived o n or in the sediment (as well as contributing to it by the dispersal oftheossicleson death). Ophiuroids probably sat on the sediment and lived 0[( organic mailer suspended in the water. Microorganisms sueh as benth ic foramini fera and ostracods lived on the sediment and , on death , contributed to ils accumulation. There are also some exa mples o f fully infaunal organ isms. These included some biva lves, such as Solemya (which makes the trace fossil , see figs 5.8 & 5.9), and polychaete worms such as Crelloscolex. Othcr benth ic invertebrates. such as many crustaceans and the limu lids, were capable of shallow burrowi ng in search of these o rganisms as prey. whilst others, such as the irregular echinoids, were deposit feeders. Of the vertebrates, sharks and rays slithe red over the bottom and grubbed arOllnd in the sedime nt for shellfish. Another section o f the vagi Ie or mobile benthic community. particula rly the gastropods. regularech inoids and starfish, was adapted to surface ~ra/ ln ~. 1 hc ..c o rg
Reefal commlillities
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.. S.lO G:lstropod; Riss()(J sp .. quarry above Gungolding-Pllalzpaint; gastropods ,lrlJUnd 5-8 mm long: JME.
~omcti 1ll es munched coral polyps. In turn ot her echinoids. many crustaceans .tml ,ma il er fhh no doubt fed on the grazers. rhere is a line di viding line between those organisms to be considered as \I ,I~ 1 1c hcntho,; and those which sett led ';0 rarely on the bottom that they ~ lln'tltute part of the nekton . No doubt many of the sma ller crustacea ns. such .t\ thc 'hnmp\ . \wam for a lorge proportion ofthc lrtime. whilst of the fish some
83
Pa/aeMc%gy
Fig. 5.11
Gastropod; Ris.toll sp .. quarry above Gungolding- Pflalzpaint; 5.5 mm long;
JME.
of the rays spent longer on the bottom. Of the more nektonie of the fi sh there were a great variety o f life styles. The sma ll , deep-bodied Gyroflchlls, ana logous to modern parrOI fish, must have been excel lently adapted to weaving it~ way through the coral branches. nibbling at cora ls and darting away from predators. Shoals of the sprat-like Leptolepitles probably swam vigorously around the reefs. occasionally gobbled up by one of Ihe giant pachycormid fis h or possibly by a turlle. Some fi sh, such as ClIlurus, with their torpedo-shaped bodies and fork ed tails, looked like the modern he rring, suggesting that they 100 were inhabitants of more open waters. To this category we must add mOSI cephalopods , certain ly the squids, cuttlefish, nautiloids and perhaps (alt hough this is more speculative) the ammonites and belcmnites. The larger marine reptiles would probably have avoided shallow waters and so the ichthyosa urs, plesiosaurs and sea crocodiles most likely lived in the open sea. The we.lker swimmers, or really floaters, lived in the quieter surface wate rs. Of these lhe jellyfish, and free-swimming hydrozoans and planktonic crinoids, were numer· ous and mosl susceptible to be ing swepl into the lagoon.
Terrestrial ecosystems The terrestrial environments to the north of the lagoon contributed plant!>. insects. reptiles and Archaeopteryx to the Solnhofen Plattenkalk . As they have been removed from the geological record by erosion. their reconstruction mu~1
Fig. 5. t2.
Malaco~tnlciln Cnl~tacC;Hl.
Mccu c/llruf 10111[/11111111111/1
berg hci Solnhofen ; length of an ill wi 1511 mm; M\A \
(S~: hh\thclm) .
M:I_'
Terrestrial ecosyslems
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• R5
Palae<Mcology
be to some exten t speculative. In all probabi lity the land was low-lying and of no great areal exte nt because it did no t supply any appreciable amount of terrigenous sed iment to the lagoon. River channels were not a permanen t feature of the landscape, but freshwater ponds probably ex isted seasonally. T here may have been a belt of wide sandy beaches fringing the land. In the hinterland, the stunted , shru bby growth consisted mostly o f gymnosperms, able to survive in this dry, sa lty soil (see reconstruction, fig. 5. 13). Seed ferns, part icu larly the widely dispersed and presumably hardy Cycadopleris, formed a scan ty unde rgrowth wh ilst squat, cone-bearing cycadophytes, deciduous-leaved ginkgos and stunted, scaly con ifer bushes were present as isolated shrubs. No logs have ever been recovered fro m the Solnhofen Platten kalk and one conclusion may be that trees were either very rare o r absent from the land immediately adjacent to the lagoon. However, furthe r to the north lay the landmasses of the ' Mitte ldeutsche Schwclle' and the LondonBrabant Massif (fig. 2.7, p. 26) and they most probably held richer plant as well as animal commu nities. The plants produced various megaspores, cones and pollen, which wou ld have supported a diverse insect popu lation . Of the insects recovered from the Soln hofen Plattenkalk , most are dependent on a freshwater habitat for the larval stages of their life cycle. Into this selling we can place the land reptiles and the renowned Arclweopteryx. The rh ynchocephalians and sma l11izards most likely spent much of thei r lives basking in the sun and running under stones. They probably ate insects and were themse lves eaten by the fast-run ning little dinosaur Compsogllatlllls (3 lizard has been found in the gut contents of the o ne known specime n of Compsognm!lIls ). The re\ativelycommo n pte rosaurs lived in close prox imity to the lagoon and with their large wings and light bodies they must have been adept fli ers. Some were probably w'lter anima ls as they have webbing between their hind toes and many ate fi sh , judging from the stomach conten ts. However, one genus, Ctenochasma, has teeth , which suggest that it was mo re likely to have been an insectivore. How Archaeopleryx lived really depends o n the funct ion we attribute to its feathe rs. The feathers of primitive birds could conceivably have served a number of purposes, such as body insulation for a wa rm -blooded beast (e.g. Bakker 1975), a heat shield (Regal 1975). an insect trap (Ostrom 1974) or for displ ay (Cowen & Lipps 1982). But it is a different, and slight ly less speculative question as to the function of the feathe rs on Archaeopteryx itself. The pri mary wing feathers, as seen on the Berlin specimen and on the lone feather, arc obviously asymmetrical and , in modern birds, th is excellen t aerofoil shape h~ possessed on ly by those who are capable fli ers (Feduccia & Tordo ff 1979). In addilion, the sha pe o f the Archaeopleryx wing and the distri butio n of different types of feathers are esse nti ally the same as in modern fl ying bird.,. So, gra nted that Ardllleoprl'ryx is likely to have flown. the debate cunt InUl" II' to whethe r it was capable of flapping fl igh t. or mere ly gli dmg. II had hCl'11 'II/-!).!l',tl'll that thc
Pulaeoecology
shoulder girdle could not have borne a musculature suitable for flapping flight (Walker 1972, Ostrom 1976), the essential points being the lack of the keel for the attachment of the muscles necessary for the strong flight downbeat (see also discussion of ArcJweopteryx's morphology, pp. 191-201) and the lack of a bony process for the operation of a pulley system to raise the wing. These objections to ArcJweopleryx's capability as a good flier were countered by Feduccia & Tordoff (1979) who pointed out that the pectoral museles involved in the downbeat cou ld attach elsewhere , in particular to the large furcula , and that the muscles used to raise the wing in more advanced birds were no t essential (Sy 1936). There seems now no reason not to accept Archaeopteryx as a capable flier. Archaeopteryx might have been either a ground or a tree-dwelling bird. On the ground it could have used its long legs for running, although it is doubt ful whether it could have run fast enough to take off. Safer with regard to predators wou ld be an arboreal life. As already mentioned, no trees arc fou nd fossilized in the Sol nhofen Plattenkalk , but Archaeopteryx could have been buried at quite some distance from its normal habitat so that this in itsclfis not a strong objection to an arboreal habitat forthe bird. In the trees, ArcJweolneryx could have used its claws to climb up trunks. It walked along branches using its wings to balance and then launched itse lf into the air. In the trees it probably ate in sects which it chewed with its small teeth . (For a furth er discussion o f the subject the reader is referred to the volume of the Archaeopteryx confe rence. edited by Hecht et 01. 1985.)
6
Taphonomy
Introduction I h;~ pite the incredible fidelity of prcserv
by differentia l decay and dissolution in the sediment. The study o f all
those processes affecti ng the potential fossils, from t heir transport inlo t he I.lgoonal waters, death (although 'dea th march' traces have been dealt with in fhe chapter on palaeoecology) and ultimate ex humation of the fossil, falls into the domain of taphonomy. This major topic is subdivided in to biostratinomy, whe re events from death to fina l burial are discussed, whilst diagenesis l'm:ompasses all those changes occurring within the sedi men t.
Biostratinomy of the marine biota rile mari ne organ isms in the Solnhofen Platten kalk lived in and around the nlw l reefs on the northern margin of t he Tethys Ocean . As monsoona l winds whi pped up storms over the sea, waves crashed against the reef and swept Wille r over into the lagoon. Occasionally, livi ng o rganisms were entrained in the now and were carried over the reefs to be submerged in the lagoonal brines. r he orga nisms of the reefa l ecosystems were, in effect, 'siphoned o ff'. Those 1II0s1 likely to be swept away were the organisms wh ich Roated in the surface waters, such as the planktonic crinoids and jellyfish. These were followed by the weak swimmers, the small fi sh and ammonites. In lesser abundance came the .. tronger swi mmers, such as the squids and cu tt lefish , and the non-anchored ilC lllhos, which induded the Iimu Iids and many crustaceans. (These groups of lIlga nisllls, in pa rticular the crinoids, small fish and crustaceans, as well as UflI ll10nite shells , comprise the greatest number of fossil specimens collected .) I he weakly attached ree fal organisms , such as the brachiopods and the shallow mfa un ll l sediment dwellers, of which many bivalves, other crustaceans and the polyc haetc worm ~ nrc examples, would be less likely 10 be removed. It would
89
Ttlpl!OIlOmy
also have taken a strong storm to have carried one oflhe larger fish. a crocodile, or a plesiosaur into the lagoon. Lastly. the strongly attachcd reefal organisms, the framework bui lders, binders, encrusters and crevice dwellers arc on ly represe nted by fragments in the plattenkalk sedime nt which travelled short distances, It is, after all, only the finest sed iment stirred up from the seafloor which was washed into the inner lagoon . In this influx , most living organisms were either left behind or else they swa m back OUI of danger. In the central and western regions of the plattenkalk area. there are cases where tens or even hundreds of nnimals of the same species are found strewn over a single bedding plane. Evidently curre nts carried away local , perhaps seasonal. shoa ls through gaps in the reef. The best example of this are the juvenile crinoid Saccocoma (fig . 7.49) and the small fish classified as Lepro/e· pities (fig. 6.4), which are bolh occasionally found in large numbers in the Eichstall qua rries. In add ition there arc numerous well-preserved jellyfish from the Gungoldi ng-Pfalzpai nt area. The abnormal regional abu ndance of ophiuroids from Zand! (sec p. 64) may represent opportunistic colonization of the lagoon noor (but not at the site where the animals are now buried). Death in al1 these cases was effectively instan taneous as there are no tracks or signs of a death struggle on the lagoonal sediment. (The few anima ls which were still alive in the lagoon are discussed under palaeoecology, pp. 77- 9). Amongst the early post-mortem features to develop was the osmotic wrinkling of norma lly turgid animals when bathed in these hypersa line solutions. a~ exemplified by some jel1yfish. In ot her anima ls there was an early contraction of tendri ls. and muscles fibres. The arms of the crinoid Saccocoma (fig. 7.49. p. 154) hnve ti ps which are strongly coiled, whilst the bases arc straight. In contrast. a slightly diffe rently constructed crinoid , Prerocoma (fig. 7.51. p. \56). has arms wit h rigid ti ps. but bilses extensively coiled (Seilacher el al. 1985). In some shrimps, such as Penaells , muscle contract ion after death Il
Bioslr(Jlil/omy of 'he marille biOla
, '" I I)!_ 6. I Disintegration and burial of the belemnite ani mal. The belemnite hard parts II I.I~ drop into the sediment and remain undisturbed by current activity. kclc tons which continued to drift aft er the soft body had fa llen away were then lU.:rusted by oyster larvae, the re lative size of the oyster she lls demonstrating Il lf how lo ng the be le mnite had drifted . When the guard and phragmocone 1I1t l1l1atcly sank to the sea bollom. it hit the sed iment with some fo rce, 11 ',lurting some of the underlying laminae. Gas trapped inside the abdomina l IIlVlly probably accounts for the poor preservation of some fish. The bent fish ~nl' ~ u s pended belly-up just above the sediment-water inte rface , leavi ng the I II l lrce 10 brush over the sedi ment surface with the scales beingscallered down ' 11111.'111. Some fish from the Solnhofen- Langenalthe im area arc evcn less well l ' I ~',c rved . The bones of the head , pectoral fins and backbone with ribs and tail "'~. ' 1111 present . but the dorsal fin. scales and pelvic girdle with fi ns are missing. [ 1II,IIIy the fish. AspidorhYllclws and 8 elollostomus. can show a peculiar kind It [lrc~ rva ti o n (fi g. 7.66, p. 175). As with other fish the post-mortem feature to .I, \·clop is the head detaching from the rest of the body, though in this case III , t ~' ;\d of the sca les being lost, the skeleto n comes away from the skin leavi ng a \"01 11.' envelope' . In Ihc plattenkalk basins the curre nts which acted on the corpses, she lls and ·,tlll· 1 fra gments were genera lly weak. but locally variable. In some of the 'I" h· te!.! pklccs. such as the Eichstiitt basin , as the bod ies waft ed down through th, will cr columll they firsl settled in a place slightly adjacent to where the body t, .,1 ,.. now found . The beltl example of:t transitory resling im pression is a I' ' "ncn (If lhe rhynchoceph:llian . KtlllimotlOIl (see fig . 7.78. p. 183). The tail , I
Taphollomy
seems to have been anchored in the mud and the front of the body swu ng around (sec also fig. 6.2 for a comparable example in a fish). In an assessment of current activity in the Eiehs!iitt basin. made at the Jura-Museum site at Schernfcld (Vioh l 1985), ammonite aptychi and fragments of ammonite shell s were all found concave-up (fi g. 6.3), a position that is unstable in a current. At other times currents may have been slight ly stronger. On the rare occasion when many elongatc fossils are found together, such as in thc Solnhofen, 'Fischflillz' (see fig. 6.4), the fossils are roughly parallel to each other and 10 the presumed curre nt direction. Overall, however, such curren t activity W(lS minimal to judge from the general lack of any current indicators. As mentioned on p. 68, the commonly cited palaeocurrent indicators of the plattenkalk come
Fig. 6.2
Circular dragnwrk :tround tish cmhclldcd in micrlttc mud , Multlhcim hei (ii.tance hetween the two point~ of lhc lnil (l() nun, JM I'.
Mi)rn~heirn:
Q?
Biostrtlfillomy of rhe terrestrial biola
Quiet water ,
Current act ivity,
concave up
co nvex up
• I"ig. 6.3 Disintegration and burial orl he ammonite animal. Note the orientation orlhe Jptychi is controlled by current activity.
lrom the q uarries al Kelhe im and Pain lcn , but these examples orseralch m arks lind am mo nite ro ll marks almost ce rt ain ly occur at the base of turbidi te beds , ;lt ld represent loca l d irections of lhe palaeoslopeof the basin fl oor rathe r th an a ~c neral pa laeocurrent direction.
Biostratinomy of the terrestrial biota Icrrestrial foss ils, such as the insects, ground-dwelling and flying repti les and IIf course A rchaeopteryx, arc some of thc best k nown of the except io nally
preserved fossils. As explained on p. 56 , the preserva tion o f the terrest rial lo..sils was initia lly interpreted as the desiccation of corpses stranded o n the ,horeline. If the muscles dried o ul , the argument went. the tendons wou ld ~' ()I\tract lU1d produce the sharply bent back neck which can be clearly recognized both in Archaeopteryx and the pterosau rs. But this kind o f feature ..:cms to be normal ror long-necked terrestrial an imals (Ostrom 1978) a nd . as ,h<;eusscd above, the fi sh which were always submerged show a simi lar fea ture. II. as discussed by Vio hl (1985), Archaeopteryx had first lai n on the sea-shore • •UI' wou ld have been trapped in the lu ngs and feathe rs and this would prolong Ihe drifling time to perhaps 30 or 40 days, by the e nd o f which lime th e body would have largely decomposed. It is thought that the best preserved o f the IrclUicopferyx specimens could not have d rifted fo r th is long. Most probably, Ihe airborne birds we re caught in high wi nds and waves and we re drowned. With Ihe lungs full o f Wliler and the plumage soaked, the bod ies sa nk to the
93
TlIp/Wl/omy
Bioslrminomy of Ihl' lerrl'Sfrill/ biO{(f
Fig. 6.4 Solnhofcn' "','III[1il1;', Ll'Pfo/l'pilieS ~'prafliforlllis Agassiz. probably from the Solnhofcn ;lr(';I, tMlur,,1 ~I/C; nSPIl GM AS I 819.
ij,
Tapilonomy
bottom (Schafer 1962. 1976. Rie tschel 1976). A rchaeopteryx came to lie on its back. chest uppermost a nd wings outst re tched o n the lagoon Hoor. Even in the best specimens, feathers a re o nly preserved on the wi ngs and the tail (a nd possibly the back of the head). In modern bird carcasses we see t he same in itial stages of dec.. y, first the loosely attached contour and down fea thers are lost fro m the buck and the breast , a nd the most stro ngly a ttached Hight fetlthe rs remain the longest. Of the Sol nhofen Platte nk alk insects, onl y Hying forms a re recorded. Th is is perhaps ha rdly surprising, the o ffsho re winds being most li kely to e ntra in the m and blow the m across the lagoon. Most insects have come fro m E ichstatt a nd Kelheim qua rries, which could be because the o riginal insect habita t lay somewhere to the east o r simply d ue to t he prevailing wind conditions. The insects may have d rifted o n the surface o f the wate r fo r a few days a nd the n sank to the botto m, in most cases with wings outstretched. Plant fragme nts could also have bee n blown into the lagoon , or e lse delive red by small freshwate r streams. In any case plant m .. te rial is ne'ler common in the Solnhofen Plaue nk alk , :lIld (as me ntioned in palaeoecology, p. 86) la rge pieces such as logs do not occur. Plant mate rial is mo re abunda nt in the beds wh ich unde rlie the Solnhofe n Platte nk alk a t Painte n , a nd in overlying beds at Daiting. The reason why o nl y small fragme nts occur may be tha t trees did not grow o n the adjace nliand , o r tha t wa te r transport was never sufficie ntly strong to ca rry them into the lagoon .
Fossil diagenesis Most corpses we re delive red to the lagoo n to be cove red immediately by a rai n of micritic sedime nt although a few which lay for a while o n the lagoon Hoor may have been overgrown by cyanobacte rial ma ts (see pp . 64-5). The micrit ic sedime nt rained down ve rticall y upon the corpses, and curre nt acti vity was ra rely sufficie nt to push sedime nt into al1 the nooks and cra nnies. Wate r· fill ed cavities wcre some times left beneath some shells, la te r to be infilled by spa rry calcite. Ammonite shells ge ne rally still contained the soft body (Seil ache r et al. 1976) and so we re not in fill ed by sedime nt a part from a plug at the aperture (presum ably because the body had been pushed baek inside the body chambe r) . The soft ooze consolidated around the bodies. Buried be nea th 11 growing pile of sedime nt the co rpses we re ph ysically compacted a nd che mically alte red . Whilst most of the fossils a re found at the inte rface between two beds with the actual body adhering to the upper bedding pla ne , some (in pllrt icular the insects a nd limulids) are a few mill ime tres above this interface a nd jU!)t inside the overlying slab. T hus the sedime nt which covers the ro\~ il mu.,1 he ch iselled away. Fos!)ils which had a cert ai n amoun t of relief til the tllue of huriul. hut
96
Fossil diagenesis
which have since been squashed Rat , have a peculiar type of preservation . Fig. 11. 5 records the sequence of events in the fossi lization of an ammonite shel l. which has left impressions on both the upper and lower bedding planes. On the tup of the lower slab the fossil stands slightly elevated from its surroundi ngs, as li on a pedestal, and it fits into a hole in the bottom of the upper slab (a feature I.. nown in German as 'Sockel-Erlwltll llg'). On the top of the upper slab there is .1 depression correspondi ng to the collapsed body underneath so that if a fossil we re present on one of the minor partings inside a flinz slab it would not esca pe .It{ention. Fig. 6.6 shows both part and counterpart of an ammonite which nicely demonstrates th is preservational feature. Pedestal structures are a ~' hanI Cieristic although not exclusive phenomenon of the Solnhofen Plaltenblk. They are also known in other deposits where soft -part preservation ,I(;cu rs, representing environments where decay was very slow and the bodies resisted initial sediment compaction. The animal bodies lay on the lagoon Roor (fig. 6.5a) and as each pu lse of ,cdimen! settled over them, a new lamina draped the bodies. This deflect ion o f heddi ng over the site of the fossils became less marked with subseq ue nt lam inae and was eventuall y evened out (fi g. 6.Sb). As sed iment continued to
• { b
I~
-::
c
i~
Fig. 6.5 Burial and diagenesis of an ammonite shell to fo rm a pedestal and socket. (a) Ammonite shell lies on the sediment surface with ils chambers full of water. (b) Entombed in sediment. (c) Under pressure of buria l the buoyant ammonite shell. without sedime nt inside, is pushed upwards deflecti ng sediment laminae. (d) Under increased pressure lhe shell caves in. (e) As the rock splits along the bedding plane the ammonite tics in a depression in the overlying slab and on a pedestal on the underlying slab.
Fig, 6,6 Ammonite Subpianiles sp, showing typical pedcstal and socket preservation ('Sockel-Erhaillmg'), On the left is, what would have been, the underlying slab with the ammonite on a pcdestaL On the right. in thc overlying slab, the ammonite lies in a derrc"'~ton, Courtcsy of the Jura-Museum, Eichstlilt. pholO W. Balling,
Fossil (ii(lgellesis
.I\'\:umu lale o n lap. water was squeezed ou t of the underlying beds. At this 'Ia~c the fossil must have risen slightly within the sed iment . as a result of Ihl1cre ntial compaction between the resista nt fossil and sediment . This e lev.1111 )11 of foss ils ca n be demonstrated in the occasional uncollapsed speci men ,,"eh as the ammonite figured by Janicke «1969 , pI. 7. fig. I) , cited in Seilacher 1'1111. 1976) where both the under and ove rlying laminae are bent upwards. The ,(\11 tissue was weakened by decay while the aragonite of the ammo nite shells pHlgrcssively dissolved. As the pressure increased , the previously resistant hudies gave way and collapsed. so thnl lam inae both above and below are ,k nected towards the fossil ( fi g. 6.5d). r he plattenkalk fossils show feat ures which demonstrate the relative timing lit ..ediment cementation and fossil diagenesis (Seilacher el at. 1976) . Some It\~"l s . notably shri mps, small fi sh and sq uids. collapsed before the sedime nt \\;,.. lith ified and produce a corresponding smooth crate r on the upper surface III Ihe bed. Other foss ils must have been more resistant and collapsed at a later \!a~c. after the sediment was lithified . Hence the ammonite Perisphinctes produces a steep-walled, fault ed 'caldera' rather than a smooth de pression in the top surface of the slab. Other
Taphonomy
Chemistry of fossil preservation Once buried in the sediment , the pore wate rs rapidly became sea led from the overlying waters and strongly reducing conditions set ill. Due to the very slow activity of the microbial decomposers , decay of soft tissue was so retarded that the shape of the fossil body was imprinted on a su rrounding mud , which already possessed a degree of cohesion. Much fi ne detail of the soft tissue is t herefore preserved as impressions, e.g. t he wi ng vei ns of insects and pterosaurs or the feat hers of Archaeopteryx. Indeed , the detailed study of the Berl in Archaeopteryx by Rietschel (1985) has revealed some very interesti ng and unexpected details. T he underside of t he wing and hence o f the feathers is preserved o n both slabs. On the main slab, which contains most o f the bones and which was the overlying slab, the feat hers are preserved as impressions and on the counter(underlying) slab they are casts. Thus the fea ther material decayed away leaving a cavity wh ich was in fi lled by sedimen t wh ich 'oozed ' from the side so taking a very early im pression of the feather. On some fossi ls the impressions are enhanced by a residue of origi nal organic mailer. For example , the isolated feather of Archaeopteryx is quite black in places . Another example o f organic preservatio n is the dry black powder found inside the ink sacs of some sq uids. which if redissolved in water will prod uce a usable ink. Cell ulose is rarely preserved in the alkaline conditions of organic-poor lime sedime nts, so plan t material is preserved only as im pressions, sometimes lined by a thin ca rbon fi lm. In some insects the impressio ns of the wi ngs are very clear because of the precipitation o f iron oxide in the veins (e .g. Libellll!illfn , fi g. 7.38, p. 144) . Mo re extensive mineralization has preserved structures that would otherwise have been lost. In pa rticular, certain parts of fossils have been replaced by the phosph ate mineral francolite. Most notable are the criss-cross muscle fi bres o f some fi sh , sq uids and insects. The preservation of the soft tissue is, of course , the except ion and the mo re usually preserved ' hard parts' account for tile majority of the fossils. Some appear to have undergone relatively litt le alteration and are close to their original composition: bones, teeth and fi sh scales are still made of cal cium phosphate . Chitin , t he resistant proteinaceous material, still apparently forms the exoskeleton of arth ropods, especially when rei nforced by ori ginal ca lci te. St ructures which were originally made of low-Mg calcite, such as the ammonite apt ychi and belemnite guards, are preserved best of all. However, those shel\<. or parts of shells made of aragonite dissolved, and ammonites . for exam ple, arc preserved primarily as impressions. Sometimes the impression is li ned with the origi nal outer o rganic membrane, tile periostracum , and sometim es calcite hat. begu n to infi ll the slight void le ft aft er the shell disso lu tion. usually fonn in~ little more than a ca lcitic fil m. Gast ropods lind some
Chemistry of fossil preservalion
.ammonites in the Krumme Lage slump beds (see p. 37) occur as thin , contorted li lms. Another relatively unstable form of calcium carbonate, high -Mg calcite, of which echinoderm plates are made , has recrystallized during diagenesis but the plates have generally not lost their internal structure.
,n,
7
The fossils
Introduction In this chapter the fossils themselves are described . They are arranged taxonom ically , in an order which trics to reflect the closeness of their evolutionary relat ionsh ips. We describe the basic construction of the fossi l o rganisms and , by analogy to t heir nea rest living relatives, show the ways in which they probably functioned . To get an idea of some of the variety of creatures which were alive in th e Late Jurassic, it is not vital to slick to a system of rigid ly defi ned taxonomic levels. I ndeed, these have been studiously avoided because
we feel that the more advanced reader would certainly fi nd any attempt
al
rigorous classi fication ulrc
become bogged down in a superfluity of lati nized names. But in genera l the major headi ngs divide the fossi ls into phyla , whilst minor headings sepa ratc ·in to subphyla and , in very dive rse groups, o rders. Usually o nly one genus is described in any detail, although someti mes others are mentioned to show the variatio n at the level of gen us. A list of recorded Sol nhofen ge nera is given in the appe ndix but it shou ld be borne in mind that th is is in need of major revision and that many of the So ln hofen fossils have not received detailed appraisa l since the last century.
MONERANS AND PROTI S TS TIle monerans are prokaryotes. the simplest of unicellular organisms without any internal organelles and d iffering in major respects from the remain ing four kingdoms of eukaryotes. T he mone ran ki ngdom includes most bacteria as well as the cya nobacteria (blue-green algae) , and these are thought to be represented in the Solnhofen Plattenkalk by small spherical bod ies. Bround 10 /1111 in diameter, observed under the scanning elect ron microscope. interpreted a~ the calcified , cell ul ar moulds of cyanobacteria. These have alrcady been discussed in detail under sedimentology, Pl' . 45- 7. In contra ... , with the monerans, protists have marc complicatcd ce lls with rncnlhmnc -bound organ e lles. such as II nucleus. mi tochondria ancl . in thc C:I'C of ph Oh)~y nlh c ... izcr:-"
,,
Plallls
\ hloroplasts. Protists were important sediment contributors to the plallenkalk "t'diment and they include the Foraminifera and Coccolithophorida, which have been discussed already in chapter 3 (pp. 44-6) with the petrography of the So lnhofen Plallenkalk. The second kingdom, the fungi, are as yet unknown in thl.! Solnhofen Plallenkalk.
PLANTS Thl.! record of fossil plants from the Soln hofen Plallenkalk suggests that the pla nt communities were not very diverse, but both land and marine pla nts are H! presented. Unfortu nately the plants are usua lly poorly preserved, most of them present as impressions, but some retain original ca rbon struct ure.
Non-vascular plants Brown algae 'phaeophytes' I'hese algae are relative ly simple multicellula r, macroscopic plants. They lived ullchored to the seafloor in coastal and shallow-water environments. A lthough they were perhaps common along the Soln hofen coast, their fossils are poorly preserved and , given their unprepossessing appearance, are not numero us in the public collections. Ma nyspecimens bear the name of PlIyllolllalius and consist of tangled masses 111 -;trap-shaped fronds resembling modern seaweeds, particularly brown algae. I he fronds have a coa rse, pimply surface, revealed by the microscope to be dumps of foraminifera and bryozoa wh ich must have encrusted the living alga. I he specimen shown in fig. 7. J is attached to a piece of reef rock si milar to the H'd ,,1 limestone wh ich occurs to the south of Soln hofen in the regio n of Nl'uburg an der Donau.
Vascular plants "Iull ts adapted for life o n land p rotect themselves from desiccation by a Illiltcctive layer of epidermal cells and tough cuticle. Water must be absorbed thro ugh the roots and it is transported through the vascu lar system, up the \tl"ln , to the leaves where photosyn thesis takes place. T he vascular system is '!le ngthcned by the development of lignified (woody) tissue. I'wo major branches of vascular plants can be recognized: t he pteridophytes, ",· hrch include the ferns. horsetails, clublllosses. and the spermatophytes , or "t'ti- IlIIlIlIS . whi ch include thc gymnosperms (con ifers and cycads) as well as
Thefossils
Fig. 7. 1 Brown alga: PII)lIotl wlllls Itlllfmfl~ ROlhplc II . I Hlljtl:lMhhl:UIl. di~ulllcc 11"'" lOp of sca..... ccd to undcr~i dc \If auached rod. 266 111m . JMI -
PlanlS: vasclliar
Ihe angiosperms or flowering plants (which did nO! evolve unti l the Cretaceous I....:riod). The pteridophytes reproduce by means of spores borne on the ,porophytc plant. which is the dominant stage in the life cycle, although they ;lI-;U havc a small and insignificant gametophyte stage, where sexual reproduction takes place. In the seed-plants the sporophyll stage is completely \lum inant, and the gametophyte stage no longer independent , but reduced to l·clls forming pollen grains and ovules (fig. 7.2). During reproduction, pollen Vf
pollen SHC
I~
sporangiumf
~." ~ ovule wilh female gametophyte
FERTILISATION IN OVULE
,
I seed I
•
DISPERSAL
GRown",
til' 1.! Reproductive life cycle of gymnosperms. The tree produces male :md fema le , Ill,· • . r..lulc cones give ri ~e to pollen gr,lins which arc blown o n to female cones of the Itlh 1'1 II different trec . Fertilization o f the ovule produces II seed on the tree which later 1.11 hllhc gfiJund and germinates. From Bra~io.:r(!9S(J). reproduced by kind permission , , ' luI\- 1II Il yman I td
Thefossils
GYMNOSPERMS
Seed ferns (pteridospcrms) The extinct seed ferns are the sim plest and most primitive of all the gymnosperms. At first sight the leaves look iden tical to fern fronds, bu t rather than spore capsules on the underside o f the leaf, there are pollen sacs or true seeds. Cycadopteris (fig. 7.3) is a common and widespread Ju rassic genus. Its fe rnlike fro nds reached lengths of more than a metre, but it is the smaller sub-unih of the fronds, the pinnae, that are more com mo n as plattenk alk fossi ls. Set o n either side of a strong centra l axis, the pinnae vary in shape. At the base of the
Fig.7.3 Gymnosperm ; CyC'tu/oplcris fun'lIstS ( Kurr) Schcnk . KclhcHIl . !cnlllh 142 m ill ; BSPII GM AS I 816h
.",
Plants: lIascular - gymnosperms
!!,uld they are round or tongue-shaped , towards the apex they become large ilud further subdivided , whilst at the tip they are again tongue-shaped. Both the pUlIJ<1C and their subdivisions have a midrib and simple , rarely forking , fine k;ll -vci ns. Specimens which are very well preserved may show that the leathery l"IlIICle on the upper leaf surface is folded over at the leaf edges and the stomata ale con fined to the underside of the leaves. These features suggest that the plant was adapted to a dry climate (see palaeoecology , p. 72). Despite the lI1a ny specimens of Cycadopteris, sporangia have never been fo und associated with the pinnae, as would be expected if the pla nt was a fern. Although the \('Ctl$ are also unknown, the plant is ascribed to the seed ferns because its Ih lLke ned epidermis is not a character typical of true fe rns.
Bennettitales I hl' Bennettitales are related to the extant cycads. Modern cycads are tropical whtropical trees with stout trunks, often short and stumpy , and ending in a 11 1)Wn of leaves. The leaves are tough, leathery and subdivided , o r pi nnate , and •• "l' lllble palm o r fe rn leaves. T he Bennettitales have flo wer-like , bisex ual \ llneS and in th is they di ffer from the cycads (whose cones are single-sex). Zam ites (fig. 7.4) is a name which refers on ly to the leaf fossi ls. From a central '"'' diverge alternating lance-shaped pinnae , all with para llcl venatio n and ~\lpcrfic ially resembling a palm leaf (see also pa laeoecology, p. 72) . Without ,I "Ilciated reproductive structu res it is hard to tell cycad {rom bennettitalea n (, I1VC!i, but well-preserved mate rial may show important di ffe rences in the hll1lata. Sphellozamires (fig. 7.5) is also probably a bennett italea n. The p innae III r more triangu lar in shape and joined to the stem at the apex of the t riangle. 1111' vCll ~tion is fan-shaped. This is the only recorded example of this taxon from Ihl" 1j,lVari:m planenkalks. HI
Ginkgos t
1111.' living ginkgo (or ma idenhair tree , Ginkgo bi{oba), which is a native of 11111u. i., the only surviving member of th is group. In many ways ginkgos are
11I1l'1l11cd iate between the Cycadopsida and Coniferopsida. Fan-shaped leaves, ,11111,' r entire or bi lobate with dichotomously branch ing venation , characte rize Ihl ~lIlk gos. In the illustrated specimen (fig. 7.6), the venation is not well P"",I: I'vc{l, so Ihat the two-lobed shape is really the only reason for placing il in 1111 j.!\.' IlU\ Ginkgo (and , incidently , there are mode rn algae wh ich also have this ~h,.pd. Unfortunately , the best ginkgo material fro m the Soln hofen Platten~ ll~ wa\ 10s1 during the Second World War. Baiera (not illustrated) is an 11111'111 tnnl ginkgo gen us with deeply divided leaves. Each leaf consists of a fan III Il1n~. linear ~cg lT1enh , eaeh about 10 em long and 5 mm wide , which are 1II111~'d III the ha\c. Thc leavc\ arc IXlrllc in cl uste rs on a short shoot which
The/ouits
Fig. 7.4 Gymnosperm: ZUllliles/elleollsis Drongniarl . Bad Abbach bei Kelheim: stalk lengt h 91 mm ; BSPHGM 1972 VI 12 .
termi nates in a thorn-like tip and these shoots are ca rried on strong, mature branches.
Conifers (coniferopsids) Today's conifers are typified by the tall trees of borea l and teml>crate dimes with their needle or sca le-like leaves. They generally have both male and
Fig. 7.s
Gymnosperm: Spht'llOzlIIIIiles Itlllfolius (Brongnillrl) Sapo.HIII ,
length 192 mm : BSPIIGM AS I Ris II .
Ei c h~tlill
TIlt! fossils
Fig. 7.6 Gymnosperm; 7Gillkgo jfabellallls (Unger). Solnhofcn; leaf lcngth 36 mm; BS PHGM AS V 39.
fe male cones. The woody female cones surround and protect the ovules which occur in pairs at the base of the cone scales and in d ue course give rise to seeds. The male cones are much smaller and expose the pollen sacs. HrachyphyJifllll is the commonest of the plal1cnkalk conifers and its leaf anatomy suggests it is related to the present-day monkcy-puzzle tree (Araucar· iaceae fami ly). A dense covering o f small sca le-like leaves is arranged in a spiral around the twigs and branches (fig. 7.7a). Cross-scctions o f the branches shO\I. an unusual feature; unlike o the r gym nosperms, which have well-developed wood , o nly the cen tral part is lignified. Th is is a feature of many modern halophyte (Le. salt- resistant) plants, so it is assumed that Brachyphyllllm livell on salty soi ls and was a weak-stemmed, shrubby plan t (see also pa laeoecology, p.72). Palaeocyparis is figured in 7.8 (sec also fig. 7.7b). It d iffers from Brachyphy/.
•
,
Fig. 7.7 Gymno~pcrm.'> of the Solnhofen 1'1:l lIcn].,al]., (ll) /lrlllllr/l/n-lllllll t",ig. (hI P(I{(lI!oc)'{Jtlri.f twig; (c) II "hroltl.II/{':' conc: (d) Arillicari,lII n lllc ~(IIIl'
Plants: vascular - gymllosperms
II ~ 7.8 Gymnosperm: Palaeocyparis prin ceps Saporta, Mornsheim beds at Daitingj 1.lIlIl h 490 mm: BSPHGM 1964 XX II 149.
the arrangement o f its leaves on the sma ller branches and twigs. The • llle ·llke Icuvcs are arranged in the shape of a letter X, with a central scale IIIl n undcd by four o thers , alt hough on the larger branches the leaves are Illunltcd in a spiral. as in Brac"ypllyllum. Both BrachYP"yllwlI and Palaeocy1,,"'1 lire relatively comnlon at quarries at Daiting in the west and Kelheim in 1111 ~'['~t. Cont!l! :Ire known only from onc gen us in the Solnhofen Platte nkalk, ""'mJlll.l."ilt.~ (fig. 7.7c), alt hough isolatcd cone sca les assigned to Araucaria (l1~' 7.7d) have 011so heen found . 1111/1 III
III
Thefossils
ANIMALS Invertebrates SPONGES Sponges are amongst the simplest of the metazoans with a bag-l ike body . variously folded in on itself and permeated by numerous canals . The body is supported by small need le-like struts, ca ll ed spicul es , made eithe r of silica or calcium carbon ate, which on occasion may grow into one another to mak e an in terconnected structure. The form of the spicule is very useful in classifying the sponges. Sponge thickets helped trap sediment and build the mounds which both underlie and subdivide the plattenkalk basins (see pp. 26-33). At the time of deposition of the Sol nhofen Plattenkalk most of the lagoona l sponges were dead and so they are rare ly found as fo ssils in the plattenkalk sedime nt. TremadiclyQn , a sponge with an intergrown network of si liceous spicules (fig . 7.9), is found in the reefal localities of the Kelheim area. It almost certain ly grew locally on the reefs, and avalanched into the basin when the sediment pile gave way. The sponge Ammollella is well known both from its body fossils, and from its spicules, which have three mutu ally pe rpendicu lar axes. CNlDARJANS
C nidarians are perhaps best known from the soft-bodied creatures such as the sea-anemone or je ll yfish which demonstrate the radial symmetry. The body has a simple design of either a tubular polyp , or disc-like medusoid. One end has all opening surrounded by a ring of tentacles. T his aperture serves as both mouth and anus and opens into a gut. Duri ng the life cycle there is oft en an alternation of body form. In the polyp stage the closed end of th e elongate body is attached to the substrate and the tentacles dangle freely in the water. In the frccswimming, medusoid stage, the body takes on a much ftatter, umbrella-like shape . The medusoid stage is the sexua l stage o f the life cycle. Jellyfish (scyphozoans)
Scyphozoans are best known in their medusoid stage , and on ly fossil m ed u ~ n have been preserved in the Solnhofen Plattenkalk . In the Scyphozoa . IIw mouth is on the underside of the bell-shaped body, is cross-shaped and
Fig.7.9 Sponge; Trellllldiclyoll .\'1)., Kapfclhc rg hei Ke lhcim ; nw'(imu(Il di amClf;'1 144 mm ; I3SPI1 G M 1975 1 1(1).
11 2
Allimals: inl1erlebrales - cllidarilll1S
, ,
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.,.
(& ~~
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Th efossils
surrounded by small protuberances. Internal part itions divide the body into four lobes and there are four o r eight gonads present. Both radial and ring canals occur. The edge of the bell has tentacles, either four or else a mulliple of four in number. The Solnhofen Plattenkalk is renowned for its jellyfish, most of which have come from the quarry region of Ou ngoldi ng- Pfalzpaint where their presence in
four different horizons is recorded. Isolated occu rrences are also known from the Eichstalt area where they are not as well preserved. The impression of the
lower surface of Rhizostom;tes (fig. 7. 10) is illustrated. Often over 50 em in diameter, this is onc of the largest , as well as the commonest of the plattenkll lk
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Fig. 7. 10 Jellyfish: RhizoslOmiles IlflmirtmdllS IIHcckcl; (IUHffy above Gungoldllll' Pfa lzpainl ; maximum di:Unclcr 32() mm ; BSP I 10 M lK75 XIV 55.
114
Allimals: iI/vertebrates - cllidorions
I' 1 1 ,; 11 ~ 1 1 It shows two zones of circular muscle separa ted by a ring canal . In the ItI hl,lk of the an imal is a cross-shaped mouth, surrounded by four gonads, I o n the outside of the bell bunches of short tentacles may just be L'rn..:d. Groups of peripheral lobes , separated from each other by deep 1 ~ l u ns. also typify the genus. An example of another platte nkalk jellyfish III the relatively rare Leplobracililes (un illust rated), smaller than Rltizos- with a diameter of arou nd 20 cm. It also has peripheral lobes but it III the possession of long, narrow oral processes and an absence of " :: ;~~:' ~:. Poorly preserved specimens of Leplobrachites are obtained from the II, I area. In the past, separate names have been given to the same species of jellyfi sh I lire preserved in differenl ways. The figured example of Rhizostomites is 1!!lpression of the lower surface of the bell ; in com mon with many such r lll1cns it shows a concentration of ring muscles. Sometimes only the middle It hll l o f the bell has left an impression. For exam ple, specimens of RhizoSfO\ dIsplaying bundles of tensed zig-zag muscles have been referred to as kll ylh h are not commonl y fossilized and their preservation in th e Solnhofen ~" ,' '' kn ll kis partly attributed 10 the hypersalinity of the water (see pp. 59-60) I II also accounts for the wrinkling of some jellyfish specimens ( presumably
I Ie). The preservation of some of the je llyfish is unusual because they .lln sediment inside the bell as shown in sectio ns through jellyfish embedthe rock. This sedimen t must have been pumped in by the jellyfish 1",,,,,' lv,,, presu mably during their death throes.
Hydrozoans the hydrozoans. the medusoid stage of the life cycle looks very similar rl l,1I of the scyphozoan jellyfish, but differs mainly in the possession of a nn the unde rside of the umbrella (the velum) that is involved with ,,,.,",";'''' , In the rare Hydrocraspedota (unfigu red) the small flan ge has fine \ tri utions. TIle gastric cavity is undivided and the bell margi n is not I • hut lobatc. The mouth is square-shaped and surrounded by four kidneyonl l processes beyond which are four gonads. T en tacles are not we ll ' I hccause they are generally very badly preserved. I
Cora ls (anthozoans) wru ls only the polyp stage is present with t he medusoid absen t fro m the yd e COnlls may live singly , as in the soft-bodi ed sea-anemone, o r as ~. "" "" ,"'II m gllni>:ms. Culcareous colon ial corals were important fra mework 1 "u l the Mluthc rn conl l reef,> , ~ u c h as those now exposed at Neuburg an 1) 11111111 J he polyp.. sc.llkd on a firm 1>UbstraIC, constructing a star-shaped I
Thefossils
basnl plate, with internal divisions numbering usually six (or a multiple thereof) and enclosed by an outer wall. As new polyps arise by budding the coral colony increases in size, its shape being determined by the species that built it. Finr fragm ents of these corals were probably important contributors to the plattenkalk sedi ment, although little un equivocal evidence of this remains . There are also some examples of the preservation of soft-bodied cora ls in tho Solnhofen Platt e nkalk . The species in fig. 7. 11 is tentat ively attributed to tho gorgonians , a group of corals with an eight-rayed symmetry. Gorgonians have a central axis made of proteinaceous material (keratin). which is on ly very rarel),
Fig. 7.1 1 ParI of n pos,ihle gorgoni;.n ; Solnhofen ; f\ISI\ V
Animals: in vertebrates - annelid worms
11hiliLCd , or else ca lcium carbona te . From this ax is arise the polyp-bearing t" ,1I1l:hcs (see fig. 7.12 , drawing of a modern gorgonian). T he branches are Ill-Ilk of small spicules of calcite which normally disintegrate on foss ilization. 111\· ligured specimen resembles the living sea-fan Iridogorgonia in its construc!lun and constitutio n , but is co nsiderabl y larger.
ANNELID WORMS
um: lid worms are typified by the soft , squashable terrestrial earthworm. The t'lllla l characteristics of the group are the segmentation of the body and the lul.ll cra l symmetry. Worms are not exclusively terrest rial ; there are a lso I1 hUIil!.! worms , some of which build themse lves a tube-shaped casing o f calcium I (I hOllate, and these are quite commonly fossilized. These worms, mostly 11,·n the generic name of SerplIla , were common encrusters in reefal environW' ·1l1\ In the Jurassic Period (as indeed they are today). Solnhofen serpulids 11 \ I II (In small pieces of driftwood and ammonite shells wh ich floated into the II uun. t here are also rare examples of free-l ivi ng, soft-bodied mari ne worms, 1111'11 lived either on or in t he plattenkalk sediment. Two genera are recog111 ,11 and the smaller of the two , Clelloscolex , is illust rated (fi g. 7.13). An 1111 pression of the segmented body can be seen together with the bunches of Io d ~ ll cs, or chaetae. It is these structures that give their name to this group of III l1d id worms, the polyehaetes. Chaetae are more prominent on the other \0 11111 , Eill/icites , and there are also remnants of the jaw apparatus. AhOlit 15 different genera and species of so-called Soln hofe n 'worms' have I. I Il named. but most of them are too poorly preserved to provide certain 1.1, 1I11hcations and , in fact , many may be fossil faeces (e.g. Lumbricaria , see Iii ~. I & 5.2 under pa laeoeco logy . pp. 75-6). URVOZOANS
I h, "ufl parts of modern bryozoans show that these animals are closely related thf,.' brachiopods, as both show the same basic construc\tion, of a ring of
401
Fig. 7. 12
Sh
modern gorgonian .
17
Tile fossils
Fig.7. 13 Annelid worm; Ctelloscolex lJrocerllS Ehlers. 211ndt; measurable length 71 111111; BSPHGM AS V 26<1. ciliated tentacles surrounding a mouth. known as the lophophore. Howeve r. in the fossilized remains of these two groups of organisms no such similari ty is apparent because all that remains of the bryozoans are the calcium carbonate casings wh ich housed the colony. The often stick-l ike tubes 3re permeated by millimetre-sized pores which represent the open ings o f the chambers which housed the original individuals. Common in reefal envi ron ments, in the Solnhofen Plattenkalk bryozoan fragments are frequent ly observed in thin-sections of coarser carbonate debris from neilr the coral reefs and as encrusters o n objects which floated into the lagoon. URACHlOI'ODS In living brachiopods. the lophophore. homologous to the feeding structu re of the Bryozoa. is also used for respiration and food gathering. Frequent l) supported internally by a calcified loop. the lophophore ofte n consists of tWI) spirals, one each side of the median plane of the valves. The sym metry of the soft parts is mirrored in the shape of the shell. Each brachiopod valve i\ bilel tem ll y symmetrical, whi lst the two va lves are of slightly different sizes and shapes. The larger of the two valves sometimes has a hole for the emergence of the pedicle. a stalk used for attachment. In some lineages of brachiopods. the ped icle may atrophy during growth or has been lost in the eoursc of evolution ary history. Today brachiopod!:! are uncommon , being \Uppl:llltcd hy the mollu"can b i valve~ in mo,t arCH\ of the world . But in JUri"'''", tU!Il'" Ihey were very
Animals: invertebrates - molluscs
common and they came in two main fo rms, the smooth-shelled terebratulids and ribbed rhynchonellids . Bm h inhabited reefal environments where they lived inside nooks and crannies. attached to the reef rock. Although reasonably common and growing up to some 10 em in size in the Kelheim area, in the Solnhofen Plattenkalk they are rare and when found are, without exception, compressed. The lerebratulid genus Loboidothyris accounts for the largest number of brachiopod species. Of the rhynchonellids Septaliphoria and IAcunosella de...crve mention. Both have a small beak where the pedicle exited the shell. Whilst Lacuflosella is symmetrical and coarsely ribbed, Seplaliphoria is slightly .I ... ymmetrical with respect to the midline of the two valves. Anothe r species of I.(lcunosella has three lobes, the middle lobe being especially broad.
MOLLUSCS Bivalves In the bivalves the shell encloses a molluscan body. Both shell and soft parts are III most cases symmet rical about the plane of the junction of the two va lves, wh Ilst each valve is generally asymmetrical about its median plane (a situ at ion which con trasts with t hat o f the brachiopods, see above). As in all molluscs, bivalves have a body wi th gut and pai rs of gills and a stro ng muscular foot .. u. . pcnded in the space between the valves (the head having atrophied). These Il(g'II1S are enveloped by lobes of mantle tissue which line the inside of the two valves and are responsible for their secret ion. The ma ntle margin has also li,kcn over the se nsory activity o f the head providi ng an earl y warning system IIl!ainst attack o r disturbance and triggeri ng the closure of the valves. rhe biva lve shell is variable in shape. and differences between gene ra can be uudcrstood in terms of modificat ions to the basic body structure as a consclltlc nce o f the habitat of the animal. Most bivalve genera today are either mfnunal (i.e. living wholly or part ly in the sediment) or semi-infaunal, l'\ildcntly as a protection against predators and also against being washed away hy currents. These bivalves need to maintain a con nection to the sedi me nt ,urface for respiration and, in some cases, feedi ng. To faci litate th is, the mant le l1Iar~II1'" arc extended into two lUbes (siphons), at the posterior end o f the .1I1 11lWI. and the shell may be elongated in this region to house these o rgans. Intnuna l bivalves may also possess a stron g foot which ca n be extruded fro m the .. hell 10 dig into the sediment. Sometimes the foot is so large that the shell l.lIl not dose properly at the anterior end, SO forming a permanent gape. IIhh.'ad or anchonng themselves in the sedime nt. other bivalves allach them,,·Ivc ... h) a I1rrn ... ub~tratc. in the ca~e of oysters by cementi ng one valve to the "lh",";1lc . Mu ...sels a l~ "ttach thcm ... c lvc!.. hut lIsing a bund le o f small protcin.11 ,'HI" Ihreud .... en lied n by'i'u'! . which is ~creted from jU'~1 behind the foot.
TheJossils
Whilst generally rare in the Solnho fen Plat tenkalk , most bivalves were of the cementing, or byssa lJy attached variety . Many are juvenile oysters of the genus Liostrea (fig. 5.4 , p. 78) , but some arc probably Inoceramus . They were attached to objects such as seaweed , twigs, bits of driftwood , bele mnite rostra and the shel ls o f am monites which drifted into the lagoon. When the floats sank to the bottom of the lagoon the bivalves died and , after detachment , beca me scattered . In some cases the remains o f t he presumed fl oat are no lo nger preserved , but its presence is inferred from the accumulation o f small isolated shells in the sediment (see palaeoecology , p. 76) . Some LiOSlrea reached quite large sizes (up to 70 em) and must have drifted for a lo ng time. Mo re freque ntly the oysters were ca rried into the hypersaline waters and killed before they reached mat urity. Of the other bivalves , a much greater diversity (although not numerical abundance) is found in the Kelheim area. There have been isolated find s of sca llops , such as Eopecte" (which was probably free-livi ng as are modern scallops), or relat ives of the present-day mussel, such as Arcom}'tifus. The narrow, triangular Pi"na was sui ted to a semi-infaunallife parti all y buried in lime sand . whilst Solemya was a shallow burrower and survived sufficie ntly long in the lagoon to produce the trace fossils (see figs. 5.8 & 5.9, pp . 81-2). A single specimen of the smooth , inequi valved Huchia has been found and this is of special significance. Buchia is a common genus in Jurassicsediments of the cooler no rthern seas. Its occurre nce suggests th at the Solnhofen lagoon was also connected to thi s northern province as well as to the southerly Tethys Ocean. Gastropods The soft body of the gast ropod is similar to that o f the bivalve in that the foot. gut , gills and o ther o rgan s are associated with folds o f mantle tissue. However . in gastropods the head is well developed and , instead of a predominantl y bilateral symmetry. in most cases the body is coiled in a spiral. The body is housed inside a spiral , conical shell which usually is not partitio ned into chambers as are cephalopod shells. The gastropod has a strong, muscular foot used to grip the substratum. As in bivalves, gastropods may have siphons which connect the mantle cavity to the extern al environment. Sipho ns or no, the shell aperture oft en has projections o r inden tations to channel wate r currents into the shell. G astropods of Late Jurassic times were both numerous and diverse , pll rticll larly in reefal e nviron me nts, and they are well represented in the Solnho fen collections. T here are low cones of the limpets 'Patella ' and the fa t spira l::; o t Globularia . Very occasionally numerous specimens of the gastropod Spilligeru are fou nd scattered ove r bedd ing planes in the Eichstiitl area . Th is Fl
Animals: ill vt'flebrales- molluscs
foss ils (see fi gs. 5. 10 & 5. 11, PI' . 83-4) , have bee n fo und o n bedding p lanes in th e G ungolding-Pfa1zpaint area. T his gastropod also has a narrow tight spiral of six to e ight who rls, but a smooth shell. RiJJO(f lives today predominantly in the intert idal zone on the seaweed upon which it feeds. The Solnhofen representatives may have been carried into the lagoon on torn pieces of algae which are no longer preserved.
Cephalopods Cephalopods arc the most adva nced of the molluscs, possessing the same basic arra ngement of o rgans but with a particu larly well-developed head and sensory organs. Primitively they all possessed an external, chambered shell. Mode rn cepha lopods are conven iently subdivided into two groups. Those with fo ur gills Hl the mantle cavity ( known tech nicall y as the tetrabranchiu tes) and, incide ntally, an external skeleto n, are represented by the nau tiloids, together with their foss il relatives, the ammo noids ( presumed to have a simil ar soft-part morphology). Sq uids, cuttlefi sh and their foss il relatives, the belemnites, fo rm the second group because they have, or are thought to have had, two gills in the mant le cavity (dibranchiate) and also an internal skeleto n. Sqllidl' and Cllltiefish I hI.! squids and the cuttlefi sh IIrc amongst th e beu er known of the mode rn ltihranchiates. They may reach very large sizes; some modern giant squids have h~ cn measured at 18 m in length . Modem dibranchiates have some o f the most highly devcloped nervous systems amongst invertebrates. Their sensory ~Ihility, co-ordinated with rapid movement , enables them to escape predato rs il nd to hunt on their own account. They move by a sort of jet-propulsio n. The Ilwntle sac, which lies undernea th the head, is inflated with water which is then l'x pclled rapidly through a funnel-shaped aperture to prope l the animal h.II,: kwards at some speed . A furthe r device used by some sq uids to escape a would-be predato r is the ink sac which may be d ischarged at an approp riate mument to confuse an attacker. In the Solnho fen Platte nkalk this ink sac is \llmcti mes fossilized . Squids (fig. 7 . 14a) and cuttlefi sh (fi g. 7. 14b) arc a rmed \\ Ilh ten ten tacles. two of which are lo nge r than the rest. T hese latte r tentacles Me retractable and have club-shaped ends, whe reas the o ther tentacles have IIll.cr.. . Fins along th e side of the body control the direction of swimming. The !l1ll' rnal ske le ton is in the form of an elo ngate plate, and is a relatively commo n 10,,11 in the Solnhofen Plattenk alk . ,'Itlioielilhis (fi g. 7.15) is the most com mo n Solnhofen squ id and its cuttle[ItUll' rClIchcs 30 em in length in the adult. Usually the cuttlebone is sq uashed 1.III"f1illy ..0 hiding Ihe sma ll stabilizers that were present at its end. At the "ppmite end of the cutt lebone arc truces o f the ri ng of tentacles which were IIIIPl~~~cd I1ltn Ihe sediment a.., the animal touched down on the seaOoor. 12 1
Thefossils
Fig. 7.14 Drawing of modern squid (a) and cutllefish (b) showing position of intcrnal skeleton.
Adjacent to the tentacles there are impressions of the jaws and mouth . Some phosphatization of the sofl parts has occurred wilh the strong siriations above the cu ttlebone, on the back of the anima l, apparently represe nting muscle fibres. The ink sac is the button·like o rgan in the middle of the body. Trachyteutllis (fig. 7. 16) has a particularly stu rdy blunt-ended cuttlebone up to 75 cm in length, with stabilizers towards the back. The underside of the cutt lebone is covered by a gra nular ornamentation in its central port ion. The
Fig. 7.15 S
Animals: il/veT/ebrales - mollllSCs
<;oft pa rts of Trachyteuthis, known from o ther specime ns. show that the animal possessed long, narrow ten tacles and broad fins which ran the length of the beast. Belemnites rhe belemn ites are an extinct group of dibranchiates whose internal skeleton is
,\ \
f
I i~ 7. III ('utclcfi~h, I'md,\,I('/lIhiJ Imrlrfoml/\ IIlI 111m, H..,PII(iM 197] V II (Ill.
l~tlppcU.
Solnhofen; cuttlebone length
Thefossils
a common fossil in Mesozoic rocks . The main e lement o f the fossils is the bullet-shaped guard, made of solid calcite, which lay somewhe re in the back of the body, perhaps acting as ballast (see reconstruction of the li ving animal, fig 7.17). Inside the guard fitted the less easily fossilized, aragonitic phragmocone , conica l in shape with a series of air-filled chambers. In the juvenile stages, whcn the guard was sti ll relatively small and light. the phragmocone could have becn used for regulat ing buoyancy (as in the nautiloids and ammonites). A thin fragile extension, the pro-ostracum (which resembles a cutt lebone) projech from the front of the phmgmocone. The most common of the Solnhofen belemnite remains arc the gua rds o f Hibolites (fig. 7. IS) . Juveniles predominate, and they are also very common in the underlying Treuchlingen marble (see p. 2S). The fossil Acolllilotellihis w", origi nally thought to be the disarticulated soft parts of f/ibo[ites but it is now recognized as anot her squid (Engeser & Rcitner 1981). Nalltiloid~'
Of the ammonites and nautiloids, abundant for much o f the fossil record, the sole living survivor is Nautilus. The shells, wh ich are oft en coiled, are sub· divided by partitions (septa) into a series of chambers. T he animal lives inside
Fig. 7. 17 Rccon~truction of belelllnite anilllal ,howing nite H\ Ull internal ~ kcl e t on
pl'{\po~cd
position of hclc11l
Animals: invertebrates - molluscs
Fig. 7.\8 Belemnite ; Hiboliles (Blainville) , Sol nhofe n; total length 176 mm ; BSPHG M AS V1l 498.
!WStaIllS
,
The foss;fs
the last chamber but maintains a connection with the inner chambers through a filament of living tissue inside a cana l, a structure known as the siphunc\e. In nautiloids the siphunc1e passes through the centre of the smooth, disc-shaped septa, which are convex away from the aperture. Being made almost entirely from aragonite, nautiloid shells, like those of ammonites , preserve poorly and, indeed, the Solnhofen na uti loids are scarcely recogn izable. 0nly one genus, Pseullagunides, can be identified with any degree of certainty. and this is because it is also known from the Mornsheim beds (p. 37) where silicified specimens are preserved in three d imensions. Psell(/(lg(lIIides has a tighly coi led, smooth shell which is sl igh tly compressed in cross-section. Ammonites Jurassic ammonites have coiled shells wit h septa that are thrown in to complex folds where they meet the shell margin, so making the typically o rnate pattern of ammonite suture li nes. Another feature which di sti nguishes them from the nauti loids is the position of the siphunc1e, because it is di splaced fro m the centre o f the septa towards the outside o f the whorls. T he name ammonile. incidenta ll y, comes from the name of the Egyptian god Amun-Re or Ammon, whose symbol, the coi led ram's horn. resembles the fossil shell . The ammon ite animal. as reconstructed in fig. 7. 19, is thought 10 have been similarlo Nautilils. Poorly preserved in the Solnhofen Plattenkalk , most ammonites are present as paper-thin impressions , somet imes lined by the outer organ ic membrane, known as the pcriost racum. Occasionally, the siphunc1e is preserved as a thin black line, a conseq ue nce of its origi nal phosphatic constitution. In most deposits the aptych i, calcareous plates located in the head region, fe ll out of l he shell and were not prese rved ncar to the rest of the ammon ite. Howevcr, a large nu mberofthe Solnhofen ammon ites are preserved with aptychi inside Ihe body chamber (and bei ng calcitic the aptychi preserve very well). T he fu nction of the aptychi in the ammonites is not known for certain. In some genera the
Fig. 7.19 Reconstruct1on of ro",m('/fi('{:",s nnimal
126
Animals: iI/vertebrates - molluscs
two t riangular plates may have formed pari of the lower jaw although some p;t laeontologists consider that they were protective covers for the body dmmber. Ammonites are important as the zone fossils which hel p to date the Sulnhofen Plattenkalk and the M6rnsheim beds (see fig. 2.13, p. 35, for drawings of these ammonites). The Solnhofen formation lies in the zone of lIybonoticeras hybollotum (Oppel), although the species itself is rare in the Solnhofen Plattenkalk. The ill ustrated specimen (fig. 7.20) is not very well preserved , but does have its aptych i, and is also encrusted by oysters. H. hyboflofllm has loosely coiled whorls without much overlap (a condition referred to as evolute), with rows of spines on both the inner and outer sides con nected by strong ribs. A long the outer ma rgin of the whorl runs a furrow, wh ich is bordered by rows of smal l knobs. A lthough H. hyboflofllm is the zone lossil for the upper part of the Lower Tithonian (ti2) in southern and central I;. urope (Tethyan province) , it is not present in northern E urope (Boreal province) where beds of this age are characterized instead by the genus Gravesia. Significant ly, southern Germany , being in an intermediate geo· graphical position between both provinces , has both Hybofloficeras and Grave\';(1. Gravesia is generally larger than Hybofloticeras, reaching a diameter of 10 em, and the whorls are evolute and qui te broad in cross-section. O n the Inside of the whorls are coarse ribs which may divide into two o r three towards the outer margin. A further two species of ammonite are restricted in range to the Upper Solnhofen Plattenkalk and younger beds, and these are fairly com mo n in relation to o ther Soln hofen ammonites. Taramelliceras prolithographicum (Fol1tannes) (fig. 7.21) is up to 10 em in diameter with a fairly narrow ape rture ,Hld a semi-i nvolute shell. Ornamentation consists of slightly cu rved, sick le, IHlped ribs o n Ihe fl ank of the whorl , with pronounced knobs towards the outside. Glochiceras lithographicum (Oppel) (fi g. 7.22) is smaller. reachi ng a maximum d iameter of 6 em. Its whorls are narrow, but more cvol ute than limlfllellicems and are o rnamented on the outer flank with pronounced sick le\ haped ribs , ending in knobs. T owards the inside of t he whorl there are st rong, broadly spaced and forward-incli ned ribs. The aperture of G. lithograplz icllm ha~ a spoon-like projection at mid flank. Neochetoceras steraspis (Oppel) (fig. 7.23) is another of the common ammonites and is up to 15 cm in diameter. T he npcrture is narrow and the inner whorls are successively enveloped by the preceding ones (involute fo rm), giving the shell a discoidal shape. (The IIIvolu lC form is nOI clea r fro m the illustration because the siphuncle of the In ne r whorl is very prominent, giving a pseudo-evolute appearance.) External urnumcnwtion is weak although most specimens exhibit some crescentic ribs which e nd in knobs towards the outside of the whorl. In contrast, the genus AIpido(;ulH", in:,tcad of being " flat coil is
Tllefossils
"-
" ./., \
.
..
•
1\ "
I
'. Fig.7.20 Ammonite: Hybolloliceras IIybollOlll1ll (Oppel) with ·Ulel'/Ifnycluj\"', Solu hofen (?Eichstiitl): maximum diameter 147 mm; I3SPIIGM AS I 566.
Allimals: illverlebrales - arthropods
,hells, others have a series of paired spines. ASIJidoceras shells were often embedded vertically in the Solnhofen sediment and specimens are always hroken. rile ca lcitic aptychi are fairly common. and there are three different types. rhose belongi ng to the genera Neocheloceras. Taramelliceras and Glochiceras have a pronounced lamellate ornamentation and are thus termed Lmn el1apty(h i (see fig. 7.23). Finely stippled aptych i are found inside the shel1s of IIpidoceras and lIybol/oliceras and are called Laevaptychi (fig. 7.20). whilst more coarsely pimpled aptychi. Granulaptychi. belong to many of the am monIte genera with divid ing ribs. ARTI-IROPODS
Cruslaceans I 'he crustaceans, together with the chelicerates and the insects. have trad itio nil lly been united under the title of Arthropoda . All arthropods are bilaterally 'YlIlllletrical , segmented anima ls wit h a hard exoske leton o ft en mine ralized by I;;l lcium salts o r phosphatic compounds. In crustaceans the body is di vided into ,I head. thorax and abdomen. The head bears five pairs of appendages, .. pccialized as antennae and as mouth parts. whilst each thoracic and abdominal ,e1!.ll1cnt typica lly bears one pair of appendages wh ich are used mai nly for wa lking or swimming. Somet imes, however, the abdominal appendages are H:duced or even lost. Often a fold of the exoskeleton . the carapace, extends hack from Ihe head to cover some of the thoracic segments.
Malacostracans Ihc..e arc lhe bcst known C rustacea of today and include the gastronomically un:cpwble lobSlCr and langoustine. The exoskeleton is fair ly well c
Thefossils
Animals: inverlebrates - QrlhrOpol/s
" Ammoni te; Glochiceras Iith o8rflphicwn (Oppel), Mornsheim beds, Morn.n"\lll1um diameter 46.5 mm ; BSPHGM 1959 XI 50.
,tn" In sh rimps the first three pairs of walking legs terminate in pincers. is either cylindrical in shape or somewhat laterally compressed IltlltllCd with a long spi ne which reaches forward over the eyes. The I , ',111 o f antennne is typically very long. In Aeger (fig. 7.24) the carapace II Int c rHlly comprcssed. The front pair of legs is of the sa me length as I, lIIi .wmg two , but bears comb-like brist les. In reptantians , which includc , I y ll ~ h . crabs and lobsters, the carapace is cylindriC<11 or dorso-ventrally ,".t rhe first three pairs o f walking tegs have pincers, the first pair of II' the klrgesL MecQcllirus (figs. 7.25, 7.26 & 5.12. p. 85) is the on ly , Iy cum mo n fossi l representative of this group in the Solnhofen Platte nIt h,I\;j very lo ng and strongly calcified fro nt pairoCwalking legs by which , Int Il\df up out oCthe sed iment and so swung its body backwards. Marks I ~" kj.!\ ma y be scen in its trace fossil. The crab-like Cycleryol/ (fig. 7.27) I 11.IIIl'nctl. sub-circu lar carapace with a loothed margin at the front and a I I on the top. The an tennae are short. The figure shows '11111,',\,dc of Cycleryo1l wit h its large first pair of walking legs. The first four • ,,' \\-alk lng legs have narrow pince rs. The first abdominal segments have a I I I down the middle and the tail fan is made of triangular sections. 7.28) is <.I true crnb because its abdomen is curled under the body II h (Ill additional appendage. It is stoutly built with a short carapace 1 ,1 IMCC
ii'
'I Ammolll tc ; Tflmmrllin·Ta.l I'rolit/wKmphicllll1 (Fontanncs). M6mshcim o\t.lIl1,hd ll1 . l'.lch 4'i 110 mm diulllclcr ; BSI' II GM 1959 X I 48.
13 1
Thefossils
Fig. 7,23 Ammonite; Neoclrelocerassleraspis (Oppel) with 'Lllmel/aplychlls·. Solnhofen; maximum diameter 138 mm: MSAV,
bearing a gran ul ate ornamentation . The walki ng legs are large , wit hout pincers. and the second pair of an tenn ae are large and cl ub-shaped. Magila (figs. 7.29 & 7.30) is a small. weakly calcified, burrowing form with a broad , first pair of walking legs and a small second pair , both with pincers. The carapace has a furrow between Ihe portions which correspond 10 the head and Ihe thorax. Bolh antennae are well developed. Another group o f malacostracnn crustaceans, although far less diverse than the decapods, is the stomatopods , or mantis shrimps. Scuitla (figs 7.31 & 7.32) is a rare genus with a compact, broad body. The segment s al the back have a comb-like edge and are ornamented wit h short gill ... The cyc~ ;Lrc o n stalk ...
132
Animals: invertebrates - arthropods
.,
1
\
i,
,
,
1
•
I
./
t ,
,., ,
'.
hg.7.24 Decapod crustacean; A eger lipularills Schlothcim, Eichstatt; carapace length 31 mm; private collection.
Ostracods Ihese millimetre-size crustaceans are encased in a bivalved carapace which is hlngcd about the a nimal 's back, so that it superficially resembles a very small lJ1villvcd mollusc. The soft bodies of living ostracods show a head unpart itio ned frOIll the rest of the body and very small , but highly specialized limbs. Unfortu nately, Solnhofe n ostracods are poorly preserved and show no details o f Ih l! soft part s. The calca reous carapaces are either smooth with a shoTt prutubl!rflnce on the side of the va lve opposite the hinges, or else weakly pitted lind lacking Ihis bulge (sec .. 1..,0 p. 46) .
Animals: invertebrates ~ art/iropods
. ~\
-- '-' "" ,
Fig,7.26 Drawing of Mecoc/iirus.
Barnacles (cirripedes)
Bnmacles are crustacea ns in which a free-living larval stage precedes the sessile adult , Barnacle larvae settle on hard substrates and, lying on their backs. comb the water with their legs, pick ing oul suspended food particles, One group, that indudes the Solnhofen genus Arcllaeoiepas, has a small body armoured by .. trong ca lcite plates and sits on an elastic slalk. A colony of this genus is known lrom the Solnhofen Plattenkalk , and this was carried into the lagoo n o n an ummoni te shell (figs. 7.33 & 7.34). Ot her barnacles form a home by bori ng into the shells of other invertebrates (although the associat ion is not truly pa rasitic), rhe slit-like openings of these excavations made by t he barnacles have been nhse rved on belemn ites from Daiti ng and are referred to by the trace foss il na me of BracltytAPfes.
Chelicerates tn chclicerates, the arthropod body is divided into an anterior and posterior \ection. The ,
,
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.
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~
,
,
"
Fig.7.27
, "
DCCllpod crUSI:ICClm: Cycferyoll {Jr0fJlm/1U11 (Schlolhl:llll) , r id,sltll 1: "11111
Icnglh 157 mill : BSI'IIGM AS V 'I.
., '
The fossils
Fig.7.29 Decapod crustacean ; Magil« l(IIim(ma Munster, Schern reld bei Eichstiitt : total length 28 mm ; BSPHGM 1964 XX III 163.
Fig.7.30 Drawing of Magi/a.
Xiphosurulls T he xiphosunms include o nc of the Plattenkalk 's most fam o us fos~ il s. Mesoli· muius (fig. 7.35 and figs. 5.5 & 5.7. p, 78 & 80). a clO'ic n:l;.tll\lC of thc modern horse-shoe crab Umll/us (see fi g. 5.6, p . 80). Tod:l)' //1/1111 /1\ li ve!'. ill .. hallow cOilstal WiHc r). and ;s fou nd in great IlUmbe r.. \111 IIll.' l'll'!l (,'nll't l)f Nnrth
Animals: invertebrates - arthropods
f,
J •
,
'f
.,• •• .
.
!-ig. 7.31 S(omatopod crustacean; SClIlda spinosa Kunth,localilY given as Solnhofen hut more likely to be Kelheimj total1cngth 32 mm; BSPt-l GM AS 1 8 12.
Fig. 7.32
Drawing of SCIf/tit,
The/Qssi/s
Fig.7.33 Barnacle ; Archaeolepas refllenbac/.ui (Oppel). Kelheim: x2: BSPJ-I GM AS 1806.
Ame rica, on some Pacific islands and in Japan. Limu lids bu rrow in the mud to shallow depths in search of sma ll invertebrates for food. They may spend short periods out of the water, and they are part icularly tolerant to " uctuations in the sa li nity or temperat ure of the water. Conseq uently. it is not surprising that they were one of the few an imals sti ll alive when Ihey reached the poisonous lagoon floor , being responsible for some of the famou s spiral tracks or 'deat h marches' which lermi nate with Ihe body at the centre. Some of the fossils are the rem•• ins of moulted exoskeletons r:llher than body fossils. In constrast to some of the crustacea ns, limulid moults are almost impossible to d isti nguish from the body fossils. This is because the shell splits only along its anlerior margi n and the animal slips oul leaving behind the intact, rigid exoskeleton with all ils appendages. More about the trace fossils and activity of M esolimlllwi in the lagoon is given in the chapter on palaeoecology (pp. 77- 9). Almost all fossi l lilllu lids from the western area of Solnhofen and Eichstiitt arc thought to be juveni les. a conclusion reached by comparison with much large r individuals from the reefal areas of Kelhcim. M esolimllllls has a large ca rapace covering the head and front of the thorax, on the top of which lire two kidney-shaped eyes. There arc six pairs of limbs under the front o f Ihe body. the first beari ng large pincers. the next five uscd for wall-into:. th e 1:. ,1 of which has a brush·like cnding and is u,ed to lever the hody 1m WllHh
A llimals: iI/ vertebrates - arth ropods
Jlg.7.34
Barnaclc; A rchaeolC/Jas redrellbachcri (Oppel). Kclhcim ; x2; BSPI-I GM
AS [807. Arach"ids
A rathe r dubious palpigrade is recorded from the Solnhofen Platte nkalk under the name o f Stertlarlhrotl . Palpigrades are relat ives of the spiders, but have legs wh ich li re fair ly long and thin and a body wh ich ta pers to a flagell um. T he body i ... a curious spi ndle sha pe and sho ws neit her the swolle n poste rior nor the division beJween the anterio r and posterior typical of mode rn spiders. Mode rn pli lpigradcs live under sto nes and in crevices and arc neve r greate r than 3 mm III lengt h. The Solnho fen example is nearer20 mm in length , so if it is generally cOlll para bl e to modern palpigmdcs it must have had a very different mode of I1fe. Insects In ...ects arc terrestrial arthropods. some of which have become adapted for a hfc in o r lI round freshwate r. They li re the most diverse gro up of all living .ulIllla ls and they also account for the greatest proportion of species in the Solnhofen Plattenk alk . T he body is divided into head, tho rax and a bdomen lind thcse are stro ngly differentiated from each other. On th e thoracic segme nt.. insects have th ree pa irs o f legs and o ften two sets o f wi ngs, wh ilst the head i.. adorned with a high ly developed set of mouthparts and o ne set of ~e ll ..ory an ten nae. All the types o r insects fossi lis..."d in the Solnhoren beds ure those which possessed ex ternal jaws covered by upper and lower naps o r nltlcle. O nly winged inS(.'Cts arc known. presumably beca use they were hl()wn out in to the Sol nhoren lagoon (!«!C also p. 86). 14 1
Tilt fossils
Fig. 7.35 Xiphosuran chcliccr:tte; Mesolimu/llS IWllchi DCSIll:lrc~t, Max bcrg bci Soln· hofen: width of carap:lce 92 1111ll ; MSA V.
The insects o f Late Jurassic limes were .. Iready fairly advanced and around two-fifth s of the modern o rders .. rc rcpresented in the Solnhofen Plaltcn kalk Characteristics al the genus and particularly at the species level are ofte n difficu lt to determine because the preservation. which is mainly as impression .... is not sufficienllyclea r. Most insects from the Soln hofen Platten kalk have c.:omc from the Eichstall quarries and a few from the Solnhofen area. Mayflies (Ephemeroptera) Mayfli es have nllrrow bod ies, gene rally aro und 3 em III le ngt h , wit h two long tail hairs (fig. 7.36). The front pairofwingl> j, l ~ .ri:c und 1111..' hind pUlr\mu ll In
142
Animals: iI/vertebrates - arthropods
Fig. 7.36 Drawing of modern mayfly .
modern mayflies practically the entire life cycle is spenl in the larval stage when the insects swim and feed on plants. The adult , when hatched . has only days, o r ,'ve n hours, to breed, lay eggs and die. The illustrated HexagetJiles (fig. 7.37) is n typica l example. Dragonflies (OdOllOta)
Dragonflies are also dependent on freshwater for the larval stage. Dragonflies h,lve a head with large, prominent eyes and short antennae. The thorax is , ho rt , wh ilst the abdomen is long and narrow, terminating in two short tail h'lIrs. Two long, but narrow pairs of membranous wi ngs with a vine venat ion oII" l' attached to the thorax. To accommodate the wings, the legs are shifted far Ili the front of the thorax. As the dragonflies are amongst the most aesthetica lly pkasing of the Solnhofen fossils, here two different genera are figured.
1·' 1t 717 Mhyny: I!t:rfl[;t'flili'. \· cdlulo.HH 11"I'11 0 r\'1 A S I ,'IOI(
Hagen. EichsliHI: IOlal length 52.5 mm ;
143
The[ossifs
Libellulium (fig. 7.38) has large, powerful wings which in the illustrated specimen are spread out, a common type of preservation. O n this specimen the delicate venation is enhanced by the precipitat ion of dark iron oxide. In Allisophlebia (fig. 7.39) the wings are folded back over the body. Cockroaches (Blattoidea) The body is dorso·vent rally fl attened and a shield covers the thorax and back of the head. The front wings are large and powerful with a characterist ic venation , whilst the hind wings are small and delicate. In Lithoblatta (fi g. 7.40) the wings are extended. Waler skulers (Pltasmida) The light body and long, splayed·out legs enable the creature to walk o n the water su rface. Chresmoda (fig. 7.41) may have lived in st reams oron the surface of the lagoon o r, as some modern forms , it might have been full y marine.
Fig. 7.38 Dragonfly ; Libell!IJillll1 /ongilal!lll1 wingspan 138 mm ; USPIIGM AS VI 36.
144
(Gcrmar) ,
Fichsllilt ; maximum
AI/imals: iI/vertebrates - arthrOfJo{/.1
Fig.7.39 Dragonfly; Allisophlebia heffe (Hagen). Solnhofen; body lenglh 92 mm ; BSPH GM AS J 804.
I ;i~ .
7.40 Cockroach; Ul/rob{fl/wlil/lllf,hilf/ (Gcnnar) . nSl'llGM AS V 13.
Eieh~'iill; wing~pun ~5 . 5
111m ;
I,
<
The fossils
Fig. 7.41
Water skater; Chresmodfl obscura Germar, Eichsliitt; body lengt h 49 mm ;
JME.
Locusts alld crickets (Ellsifera) The e nsiferans have particu larly long hind legs which are well adapted for jumping. Their heads are large and the an te nn ae a re as long as the body, o r longer in jumping forms. Burrowing forms are also known. T he fema les are recognized by their long ovi positors, so we ca n deduce the figured specime n to be a male. A la rge numbe r o f the smaller insects are included as crickets under the label '£/cana' , but their gen us is difficult to determ ine owi ng to their poor preservation. PyCl/ophlebia (fig. 7.42) is the most common Sol nhofen locust. T he ante nnae, measuring some 13.5 em, are longer tha n the body. As in nearly all cnsifera n speci mens, th is one is laterally e mbedded and not very well preserved. Bugs alld waler scorpiolJs (Heteroplera) The forewing is hardened and covers the membranous front half of the hind wing. The back is covered by protective shields, firstly a thoracic shield and then behind that a triangular field which is bordered by the underside of t he partial wing cover. Both land and water forms exist , a nd even the water forms are excellen t fliers. Mesobelostolllilm (fi gs. 7.43 & 7.44) is ve ry si milar to the gia nt American water scorpion (fig. 7.4S) •• t!though it does not reach q uite such
Fig. 7.42 Locust ; Pycnoplrfebill roblls/a Zellner. locality given II~ Sc.lnhoren bu t is more probably Eichstiitt ; length along body and wing 121 111m , Il ... PI 10M IIt'i2 a 247. 146
Animals: inl'f!flebmlcs - uflhropods
147
Thefossils
Fig.7.43 Water scorpion; M esobeJostomllf1l deperditllm (Gcnnar). Eichstatt: body length 70 mm; BSPHGM AS I 538a.
Fig.7.44
148
Reconstruction of M esobelo.uolfl ll ll1 .
Animals: im'erlebraleS - arthropods
Fig. 7.45
Drawing of Nepu. modern American water scorpion.
an extre me in size (som e mode rn form s of over 10 cm are known) . Water scorpions li ve o ff young fi sh and other small water creatures. From lime to time they cl imb to the water surface fo r air.
Cicadas ('A llc!Jellorrylmc!Jans') fhe forewings are seldom strengthened to the extent of the hind pair. The wi ngs, which may sometimes be quite wide and butterfly-li ke, are fo lded back over the body when not in use . The hind legs are long. A Solnhofen representative ( not ill ustrated) is A rchepsyche. Lacewings (Neuropterans) A'i in the beetles and wasps, bot h pai rs o f wings are o f simila r, large size, wit h long straight veins, interconnected by a system of thin ner veins, although deta ils of the venation va ry between the wings. Some lacewings look fa irly ' Im ilar to the bUllerfl ies, but at rest lacewings fo ld the wings back over the ilbdomen, whilst in butterfl ies they re main clasped together and vertically crecl. In addition the antennae are between the eyes rather th an in fronl. Ktllligramma (fig. 7.46) is the la rgest insect from the L1te Jurassic. It is rather different fro m modern examples and so may have had a different li fe style. In this specimen , one of the forewings is not preserved. Beetles (Coleoptera) rhe ch itinous integument of bee tles makes a strong, protective armo ur. The fro nt pair o f wings fo rm the strong wing-covers, or elyt ra, beneath wh ich the hind wi ngs are fo lded . Beetles have ta ken over many habitats, even freshwater. rhey are re la tively commo n in the Solnhofen Plattenkalk, but unfo rtunately ,how few cha racters use ful in their cl assifi catio n. In fi g. 7.47 Cerambycillus, a po~s i blc relati ve o f the modern wood beet le, is shown. Promine nt is the square head o f the beetle, the relatively short .lbdomen wi th large. granu late elytrd, lllld th e illl press i on~ of the long I~gs,
The/ossifs
~~
~~"'''-'.''-.'-: .... '"" • 't -
,
•
•
,
Allimals: invertebrates - arthropods
I ,g. 7.47 Beetle: Cerambycilllls dllbill.~ Gcrmar. locality Sol nhofen, or perhaps Eichbody length 21.5 mm ; BSPHGM AS VII 354.
~t iltt :
lVasp~'
(Hymetloptera)
Wao;ps are characterized by two membrano us pairs o f wings and the fa ct that the fi rst segment of the abdomen is fused to the thorax. Females have a lo ng, ~h arp ovipositor used for stinging , pie rcing o r sawing. Pseudosirex (fi g. 7.48) is thought to be a relati ve of the modern giant wood wasp, S irex. The wood wasp k ma lcs bore into dead trees , using t heir ovipositor spines, and lay their eggs lU\ldc . When the larvae hatch. they feed on the wood . wh ich also she lters ' hem. I, is qui te li kely that the Jurassic wasps had simi lar habits. The il lustrated \'x arn plc carne to rest on its back , on what is now the bedd ing plane. and so the kg~, which arc inside the slab , are not visible. T he long antenn ae arc lost but ,he wing ve nation is excellently p reserved .
I I)I..7
Luccwmg; KII/Ji~rtmmlllllllt'"Ckell Walther, Solnhoren ; maximum wingspan BSP IIG M 11,1(12 16.
lSI
The fossils
Fig. 7.48 Wasp; Pselldosirex sdrroeleri (Gcrmar), Solnhofen ; total length SOmm; IGPTUB . Photograph by B. Klccberg. Caddis flies (Trichopfera)
T he wings , which are very hairy , have only a few cross-veins. The th ree main veins in the posterior sector unite around the margi n of the wing. The Sol nhofen Pl attcnkalk has yielded such genera asArcholall/ill s and Mesolaulills (ncilher illustrated). Flies (Diplera)
The hind wings are diminished to drum -like organs which swing during Hight, act ing as gyroscopes. The mouth organs are designed for piercing and slicking and the eyes are genera lly large. Classifica tion of the Solnhofen nics is in need of revision . ProhirmOlleura (no t illustrated) is an ex ampl e from the Soln hofen Pl atten kal k. I ;?
Animals: invertebrates ~ echinoderms
ECHINODERMS Echi noderms are a group of marine animals with a skeleton of porous calcite plates. Technically this is an internal skeleton , although in life the test is only covered by a very thin layer of soft tissue. On death the plates may disarticulate but , at least in the echinoids (sea-urchins) , this happens very slowly and e ntire tests are quite commonly fossilized. Echinoderms are characterized by a pentameral symmetry , although in some forms a bi lateral symmetry has been supe rimposed. Openings in the test included a mout h and anus, usually o n opposite sides of the skeleton, as well as pores for the protrusion of tube feet which help the animal to maintai n a connection to the outside world from inside its calcite box. T he tube feet are all inte rconnected and work on a hydraulic system , known as the water-vascular system. This is a diagnostic feature of all echinoderms. In outline , the system consists o f a ring-shaped canal that connects to the seawater via a perforated pore on the top of the test. From this ring canal arise five major branches , terminati ng in the tube feet which protrude fro m the paired pores. The areas of the test containing these paired pores are termed ambulacra, whi lst the rows o f interven ing plates are called the interambulacra. Both ambulacral and interambulacral plates may be covered by spi nes.
Sea-lilies (crinoids) The majority of crinoids in the fossil record are o f the attached , sessile variety. A stalk anchors the main body of the ani mal, known as the cup (or calyx) , to t he substrate. The mouth projects upwards and is surrounded by five (or a mul tiple thereat) arms (ambu lacra) which bear hair-like processes , known as t he pinnules. Bo th arms and pin nules have tube feet which trap food particles. O nly one gen us of sessile crinoid (Millericrim ,s) is, however, recorded from the Solnhofen Platten kalk, the remainder being free-swimming forms. In these latter forms , the stalk is either lost entirely o r reduced to small movable processes that arise on the side of the calyx opposite to the mouth and ambulacra. SaccQcoma (figs. 7.49 & 7.50) is by far the most numerous not on ly of the crinoids, bu t of all the Solnhofen macrofossi ls. Specimens of Saccocoma , particu larly the juveniles with ca lyces on ly a mi lli metre in diamelCr, are ve ry common on some bedding planes in t he Eichstatt area (see p. 90). The mature anima l is not much bigger , not exceeding about 8 mm in diameter. Protruding fro m the ca lyx are te n ambulacra with pi nnu les which aided swimm ing. Pterocomo (fig. 7.5 1) is also II fairl y common fossil , although not in comparison 10 Saccocol1la, Hnd many spe cimens have come from the Zandt and Eichstatt q uarries. Pterocomfl i" much la rger Ihnn Saccocomll , th e arms being up to 10 em in length ami pU),..C.... II1 ~ lu ng. deli cat e processes.
Thefossils
Fig. 7.49 Crinoid; Saccocoma lenellum (GoJdruss), Solnhofen; maximum distance between the anns 40 rom; SM F11252. Photograph by K. Harvey. Cambridge University.
Starfish (asteroids) Solnhofen starfish do not look much different from today's forms. The five arms merge into the central portion of the body which has the mouth on the underside. T he underside of th e arms is cove red by enlarged plates out of which emerge tube feet. As both sta rfish .md brittle stars normally fall apart during the fossilization process, the articu lated specimens from the pla ttenka lk make a substantial cont ributio n to our understanding of the evolution o f these groups. The Solnhofe n ge ne ra .Ire relatively large. wit h diamete rs of up to 15 em. However, all arc rare li nd the figured Lithasler(fig . 7,52) ... particularly uncommon . 154
AI/imals: iI/vertebrates - ec/lil/oderms
~~
Fig.7.50 Drawing of Saccocoma.
Brittle stars (ophiuroids) Ophiuroids are typically smaller and more fragile in appea rance t han the asteroids, with the body disc d istinctly demarcated from the lo ng si nuous arms. rhe arms are strengthe ned by a series of fused ambulacra l plates which resemble vertebrae and permit great mobi lity of the arms. Ophiuroids are mai nl y sllspensio n feeders. Geocomo (fi g. 7.53) is very abu ndant in ce rtain beds o f th e Zand t quarries. rhe body disc is small in proportion to the le ngth o f the arms, and the overall diameter is around 6 em . Ophiopsammlls (fi g. 7.54) is larger than Geocoma with the body disc relatively larger in comparison to arm length . Characteristic fcatu res include a granulate pattern on the body disc, whieh is also prescnt on the underside of the arms, a ridge over the upper arm plates and the presence of ~ma ll arm spines. Ophiopsammlls may be quite common in some parts of the Kclheim-Weltenburg regio n.
Sea-urchins (echinoids) h .:hino ids have a globular test covered by spines. T hey are like starfish if o ne Imagines the arms or ambulacra curled back away fro m the mouth and joined at thc top of the animal, and the ambulaera became interconnected by interambuliler:.1 platcs. Both the al1lhulacra tlTld interambulacra may have spines. ulthough ~Onu.'tIIt1c~ uf ,!lnC-fent ~hapcs. The spines articula te by ball and 1'\5
Thefossils
Fig. 7.51 Crinoid; Pterqcomapellllata (Goldfuss), Zandt; maximum distance between the arms 100 mm; preparation, photograph and collection by Captain G. Brasscl , Flensburg-Murwik.
socket joints to rounded bosses on the underlying plates. Shortly after delli h the spi nes fall away and become sepa rated from the animal. However. in Iht· plattenkalk , echino ids are found wil h their spines sl ill attached . The general shape of the test distinguishes two typcsof echi noid. T he regulal' ech inoids, wh ich in IOOay's reefal environments are main ly surface grazers and predators, arc equipped with a strongly tooth ed jaw on the underside of th l' body and an anus al the opposite side of the apex. Telragramma (fig. 7.55). OIl around 5 em in diameter, is an example of a fairly small regular ech inoid. It hOI" (and had, before il was squashed) a fairl y flat lest and a mosaic of broad plalc" around the anus. It kept predators al bay wi th a hedgehog-like arrangement 01 fairly large spi nes. Their al1achmcn l bosses arc preSe l11 in tWO rows on each ambulacrum whilsl on each inlerambulacrum there lire four row\ in Ihe CC ll1rc Ranked by two rows on e:lch 'lidc. The spine .. arc .. llIIrl . poin1cd lind finet)'
Anima's : in~·ertcbr(l/e.f - echinoderms
11.\ 752
Asteroid ; Lit/wSler jllmssiclis (Ziltcl), B6hmfe ld southeast of Eichstiitt ; dislance be tween the tips of the arms 140 mm ; BSPH GM 1847 1 502. l'llolograph W. Suter, Naturhistorisches Museum. Basel.
11I;1~ lmum
,II ial cd . T he re arc also seve ral gene ra of echi noids from the cidaroid group in Ihl' Solnhofen Platt enkalk . These have ve ry large cl ub-shaped spines which 1II •• y have hcen e'>l>ccially effecti ve HI dClerring any would-be predato r. These l'l h,1lI1;d'> have a le,>1 o f rc lul lvd y few IMge plates wi lh prominenl bosses.
,.,
Thefossils
Fig. 7.53 Ophiu roid ; Geocomfl carinara Goldfuss. Zandt; maximum distance between arms 58 mm ; B5P II GM AS I 555.
,
I
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t
.,
,
I
......... • "".
Fig.7.54 Ophiuroid; Ophiol'Sllmllllls kt'lIlf!illlt'lIsis ( Boehm). Weltcnburg bci KcI hd m: BSPIIGM 1965 XX III 42.
15R
Allim als: iI/ vertebrates - echilloderms
•
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hg. 7.55 Echinoid; Tefrag ramma sp., locality recorded as 'Solnhofen' bUI faci es is illore Iypieal of Kelhei m; di ameter 50 mm ; BSPHGM 1878 V18.
In the irregular echinoids the mo uth remains o n the underside of the animal (ulthough it is o ft en di splaced from its central positio n), but the anus has migra ted from thc apex to a posterior position. In Collyropsis (u nfi gurcd) the tc~t has the typical hCHrt·sh ape in plan view. T he pentameral symmetry of the heaM ha" bee n di sruptcd by tlte impositio n o f a bilate ral sym metry that re fl ects the grellter mobil ity of the Ill1 inHl l as it burrowed through t he sedimen t. PUr'''lI lIIg it~ life 11\ it dcpol>lt feeder.
159
The fossil$
Sea-cucumbers (holothurians) I-Io lothurians are shaped like stretched-out ech ino ids, the mouth at o ne end . usua lly surrounded by tentacles. and the an us at the o ther. Moreover. calcll rcous plates are reduced to small microscopic ossicles, isolated fro m each other lind embedded in the skin . On dea th the ossicles disperse. with the large numbe r making them an important cont ribution to the sed iment. The forms which live on the seafloor arc protected by a leathery ski n. whi lst those wh ich burrowed are more delicately built. As expected, given their effectively soft -bodied nature, the fossil record of ho lothurian body fossils is extreme ly meagre. Thus the Solnhofe n specimens . although of very poor quality, arc of great palaeontologicul importance. PrQloilolotllllria (unillustrated) serves as an exam ple although it is extremely rare . It has a tube-shaped body, around 6 cm in length , with a coarsely granulate outer surface, and one e nd beari ng fi ve to six indistinct. shrivelled tentacles. In some silicified portions o f Soln hofen Plal1e nkalk , the cnicile ossicles o f holot hurians may be replaced by silica nnd so may be dissolved out of the sediment by acid preparation in the laboratory. The small (0.1-0.3 mOl) plates differ in shape and are assigned to various form-genera and form-spec ies. It is recognized that these names are unlikely to correspond to original taxa of holothurians in as much as seve ral ossicles of diffe rent sizes and shapes we re present in the same body.
Vertebrates nSI-I
The fi sh arc by far the most nume rous of the Solnhofen vertebrates, primari ly because a few genera are found in grea t numbers at certain loclliities and strat igraphic leve ls. Most genera arc. however, quite rare and o nly known from a few specimens. The Solnhofe n fish may be conveniently classified into wellknown living groups.
Shark-like cartilaginous fish (Chondrichthyes) This includes th ree separate groups, the sharks and rays and the more di stantly related ratfish . Instead of the heavy bony skeletons of their anccstors, th eir skeletons li re made of the lighter lind more flexibl e mal crial , cartilage. A primitive characteristic present in both the Solnhofen and modern-day cartilaginous fi sh is a body covcring of dcnticles o r skin teeth. Each denticle con tain'i an inner pulp cavity surrounded by dcnline with nn ou teT coa ling o f enamel. The similarity be tween this arrangement and ou r Hwn Il'l' lh IS IllOTe than coincidental .... they 1lI0'i1 probahly cvolVl'd from dtrHrlk, I1l1lhe ~klll coveTIng
Animals: I'ertebrares - fish
the edges of the jaws. In cartilaginous fi sh the water necessa ry for res pira tio n is drawn in through the mouth on the underside , as well as through a pair of circular structures known as spiracles (actually mod ified gi ll slits), and passed out through the remaini ng gill sli ts. which a re usuall y located o n the side o f the animal. Sharks (selachialls) Sha rks move by s inuous curves of the tai l, particularly o f the upper fl a nge, wh ich provides t he forwa rd thrust. The body, being torpedo-sha ped , is ... treaml ined a nd the backbone may be weakl y calcified fo r stre ngth . T he large lateral fin s, o r pectora l fi ns, act like t he wings of a n aeropla ne providing a n upwa rds thrust which counteracts the weight of the head and the te nde ncy o f the a ni mal to nose-di ve. As the o ve rall body de nsity is greate r than the wate r, ... hnrks m ust sti ll keep moving in order to re main nfl oat. The continual "wimming makes the m either act ive hunte rs searching fo r and chnsing prey, o r else suspensio n feeders filte ring the seawnte r. Sha rks' teeth a re usually shar ply pointed but in some forms the re mny be fla ller teeth adapted fo r crushing. The jtlW is not a ttached to the brain case, but is supported behind a mod il1ed gill arch . Fi ve types of sharks are recognized fro m the Soln ho fe n Platte nkalk. T he Galeoidea cont ains the majorit y o f the living sha rks, most o f which a re harm lcss c no ugh , a round a met re in le ngth, nnd inhabiting a rcas o f the wo rld's ocea ns. Ma ny are to be found in the Nort h Sea , whe re t hey fe ed o n fi sh. A mongst the Solnhofe n assemblage Palaeoscyllium (fi g. 7.56), has the typically long and narrow body o f the galeoid sha rks a nd promi nent unpaircd fin s, two dorsal a nd one a nal, without supporting spines. The paired fi ns a re visible, .l lthough o nly in oblique orie ntation , a nd the tip o f one o f the pectora l fi ns pT{llrudes slightly a bove the head. The vertebral colum n is very promine nt , as the ve rtebrae are heavil y calcifi ed . In the fossil, the gill slits a re no lo nge r recogn iza bl e and th e spiracle is known 10 be absent in this genus. T he le ft eye uppears slightly e levated from the surface, whilst the right o ne, wh ich is onl y Just visib le, is pushed to thc top of the skull. T he teeth (no t rea ll y visible in th is photograph, but relat ively frequen tly found de tached from the body) have ,ha rp cutt ing edges wilh o ne mai n po inl , or de nt icle , and som et imes smalle r u\\(}ci.. ted denticles, I' ,\'el/(Iorllill" ( fi g. 7.57) is placed in the Squaloidea . This type of sha rk fl'"ernb lcs a ray in ils dorsa-ventrall y flatte ned body, well suited fo r gliding over the sCHfloo r. Un like a ray, the gill sl its (accompani ed by a la rge spiracle) open on the side of the a nima l a nd the mouth, with sma ll ras ping tee th , is , .tunted al the front o f the head . In addit io n , t he pecto ral fin s a re very large a nd dearly ~c para t ed from the head , the pelvic fins bei ng somewha t sma ll er. As in 11 11 "'lua loid ~ h urk." the re i~ no anal lin and although Ihe spines supporti ng the tlor"ul fin., do occur in rciat cd ~('nera, suc h as Prolospillux (un figurcd), in I lu, tlllar/1I1/1I the)' Ufe nh'l,.l1 1111' vertehrae afe weak ly o~~ ifie d ,
Tile fossils
,• .,..:~.
'J ,
, Fig.7.56 Shark; Pu/ueoscyl/illm formosum Wagner, Solnhofen; length 313 mill; BSPHGM AS I 589.
1111
Animals: vertebmtes - fish
Th e fossils
(
1
.
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,/ " "
•
11\.1
Animals: verlebrates -fish
Rays (batoideatls) Rays have aba ndoned the life of -(:ontinual motion needed by most sharks to keep them in mid-water. Instead they Jive on the boltom, camouflaged or sl ightly covered by the sedi ment . T he tail is now no longer o f prime importance in swimming and the muscles have di min ished leaving a whip-like o rgan useful only in navigation. Th e ray moves by passing ripples along the pectoral fins , which arc very large and fused to the head . The mouth is o n the underside of the animal as rays feed on moll uscs lind crustaceans fro m the seafloor which they chew with a battery of sma ll teeth, united in thick rows, or in a chewing palate. A current of water must be supplied to the gills, but to avoid also inhaling sediment, water is drawn in through the spiracles on the top of the head and then ejected through the gill sl its which are always on the lowersideof the body. Fig. 7.58 shows Aellopos, probably a relation of the modern 'guitar fis hes', such as RhinobalUS. It does not show the extreme flatn ess o f some of th e rays and is still torpedo-shaped, like the sharks . although it is widened laterally by its pectoral and pelvic fins. However, the pectoral fin s pass int o the side of the head and the mouth and gills are on the underside making A ellopos a true ray. Dorsal and tail fins are also well developed , the dorsa l fin s each supported by a spi ne. This example is a ma le and is recogn ized by the supporting strut s of the pectora l fin s. Chimaenformes, ratfislr (holoceplraliatls) This third group o f cartilagi nous fish is o nl y distantly related to the sharks and the rays. The upper jaw is fu sed to the skull for extra strength . and hence gives the name to the group, Holocephali . The vertebrae are not additionally "deified . The few teeth are strong and flat ratherthan pointed and are used for l'fushing shellfish. Unlike the sharks and rays the gills are protected by a lobe of .,ki n. which is not dissimilar in construction to that of the bony fish. The first dorsal fi n is suppo rted by a stro ng spine. Ischyodus (fig. 7.59) is II typical Chimaera , o ne of the two types o f Solnhofen ratfish. The head is particularly large and slants forward , whilst the body tapers backwards produci ng a ~tream lined shape. The spine of the first dorsal fin is clearly visible be hind the head whi lst the second dorsal fin is e longate and of small size. Both paired pectoral and pelvic fi ns are large.
Hony fish (Osteichthyes) Hoy-ji'wed fish (act; lIopterygiolls) Of the bony fi sh , the main type found in the Solnhofen Plattenkalk are the rayhnned fi sh, so called bcC;:IUse the fins arc supported by stro ng bo ny rays or hI! . 7.~7 Shark ; 1'\'j'/11lorll/ll/l 1IIIfail HSPIIOM AS Vll 4
(MlIn~lcr), Eich~tatt:
tot:ll length 463 mm ;
,
..
Thefossils
166
Animals: vertebrates -fish
spi nes . There are three groups, two of which , the Chond rostei and the Holostei, may be intermediate in the evol ut ionary road to the modern bony fish , the Teleostei. Cart ilaginous ganoid fis h, or chond rosteans, may be conside red the most primi tive. They are covered by a restrictive coat of thick, enamel-covered scales (ga noid scales). The scales are finnly held together in rigid circles around the body , but these may articulate between one another. T his allows the body 10 bend side to side in snake-like movements, but not to change in shape. The vertebrae remain unossified. The tail and pectoral fins are still requi red to produce an upward thrust for the heavy body (even though the fis h may possess a swim-bladder). T he tail shape remains asymmetrical with the upper flap "upported by the vertebral column and the lower flap fles hy and not covered with sca les. A living relat ive of the chondrostea ns may be the caviar-producing "t urgeon. From the Solnhofen Plattenkalk only one species of the gen us, Coccolepis (unfigu red), is recorded. Bony ganoid fis h, or holosteans, make up most of the Sol nhofen fish. A bony Inner skeleto n takes over the function o f moveme nt regu lation ma king the "trong and heavy scale coating of lesser importance , especially for those fo rms which are rounder in cross-section and less suscepti ble to distortion. Sca les are IIlte rmediate between rhomboid ganoid scales and overlapping round cycloid 'icilles. T he tail is genera lly smaller than in the chond rosteans and in some forms may be almost symmetrical. A swim-bladder enables the fis h to be neutrally buoyant. The mou th region has become shortened and the upper jaw more manoeuvrable. The specimen o f Lepid otes (fig. 7.60) is the most noteworthy o f the Solnhofen holosteans because of its extremely large size , which may reach 2 m in length . Il owever, en tire specimens o f Lepidotes are generally very rare. The t hick, l' l1 amel-covered scales are very prom inent and arc more often found d isarticulatcd from the skeleton, as are the hem ispherical teeth. Gyro fi c/IfIs (fig. 7.61) , belongs to a different grou p within the holosteans, and rese mbles the modern parrot fish. T he body is very th in and disc-shaped , ~ upported in ternally by a delicate network of bones , and the front part is ~' ()vc rcd externa lly by large scales. The fis h manoeuvred by the dorsal , ventral +lI1d symmetrica l caudal fi n as well as the rela tively sma ll paired fins , e nab ling UvrO I1c/IIIS to weave between coral bra nches. Gyrol1chus, as well as its larger relative Gyrot/us , has small round teeth (fig. 7.62), which in the parrot fish are udapted for chewing co ral.
II ~_ 7 . 5~
Ray: Al'lIop Ol IJIIRC,I;(/CIIJ (ThiolliCrc ), Langcnalthc im: width of PCCIOTllt 1\20111111 , BS PIIOM AS I 'i( )(l Copyri ght of Ihal collection. Photograph M. I lrc,~ l cr ,
IlIt~
The fossils
Fig.7.59 R:ltfish; /schyodlls qllensledli Wagner, Eichstiitt ; lengt h 1550 mill : B$PHG M 1954 I 366. Copyright of that collection. Photograph M . Dressler.
, Fig. 7.60 Sl!lllionotifoTIll. h()I\)~tl!a n fhh; tl'pilJOII'1 mUll/lUll WIIJ.tllcr. I Jlllgclllll Ihci m; lenglh 2tl.'i1l 111111. NMSI' P 2~~l!. CUI)) Tij.:hl nf lhul mlN·um
Animals: vcrtebrllfes - fish
1(0
Thefossils
f
I ...•
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,
Fig. 7.61 Pycnodontiform, holostc.tn fish; GyrollchliS mllcroplerus (Wagner). Blumenberg bei Eichstiin; total1cngth 162 mm : BSPHGM 1939 1 19.
Calurus (fig. 7.63), with a streamlined body and al most sym metrical deeply forked tail, must have been an agile and fa st-moving swi mmer. It 100 possesset\ a thick cove ring of scales. which conceals the vertebral col umn . Juven iles (such as the fi gu red exa mple) sti ll had unossified vertebrae whi ch do not preserve well. On the ventral side the intestinal contents are preserved in phosphate. The related Urocles (unfigured) has a body shape which indicates that it too was a good swim mer and an active predator. It is easily recognizable from ils brushli ke tail. The remains o f smaller fish on which il preyed have been foun d in the gut o f some specimens. Urocles specimens arc peculiar ililhal they have never been found on the beddi ng planes, bu t OCCU I" in .. idc llilll UI1II~ olllllinOI" planes
170
Allimals: vertebrates - fish
Ilg.7.62 Teeth of Gyrodlls cirClllaris Agassiz, Solnhofen?, approximately natural \ II.C:
BSPHGM 1972 XX 137.
of weak ness. From another related fami ly comes Histionotu$ (fig. 7.64), which
hils very large and disti nctly shaped do rsal and caudal fi ns which could have enabled precise naviga tion amongst the reefs. A very different shape is demonstrated by the e longate . pike- like Aspidorhynchlls (fig. 7.65) and related BeJollostomus (fig. 7.66). The scales are large on the flanks but small on the underside and back. When the fish died and started 10 decay the scales tended to stay together and become detached from the underlying tissue as a scale envelope (sec p. 91). The best-preserved specimens arc of moderate size and have been obtained fro m Zandt and Kelheim . Lastly PllOlidophorlls (unfigured) is a holostean which possesses some of the Iwits of the modern bony fish , the Teleostei. In o utli ne Pholidophorus looks ra ther like the modern he rri ng and it may have had a sim ilar life style. The body " spindle-shaped and the tail symmetrical. The sk ull shows the 'adva nced characteristics' of a movable upper jaw. and in a re lated genus t he lower jaw protrudes over the upper. The vertebrae are fully ossified. The armour o f sca les 1\ li ghter , the scales being thin ner. Modern bony fis h , or (eleosts, have a skeleton which is completely ossified li nd supports the body. The scales, which are no lo nger needed for support , are ~ lI1atl and round and constitute the body covering. The body is a simple spindle ... hapc with a deeply forked symmetrical tail. The uppe r jaw is movable. A ll of the Solnhofen fi sh be long to the same group as the modern herring alt hough ~O I1l C reached a size of around a metre. The aesthetically pleasing PachYlliris\ /JpS (fig. 7.67) is a typical exampl e . The sprat-like fis h assigned to the ge nus 1A!IJ/olepides ( fi g. 6.4, pp. 94-5) are undoubted tcleosteans but a re probably luvc nilcs belonging to a variety of separate species. These sma ll , superficially ~ il1lita r. fi sh occurred in swarms such as are preserved in the so-ca lled Solnh orl!tl " Fi,fciiflill z' (sec p. 92), 17 1
The fossils
Animals: L1erlebrates - reptiles
Lobe-finfled fish (crossopterygia lls) T hese are also bon y fish but only distantly related to the Acti nopterygii . The lobe-fi nned fish are very important in vertebra te evol utionary history as one group of these is thought to have given rise to the amphibians by the development o f li mbs and an internal nostril. The coelacanths lack an internal nostril, and have modified the pri mitive lung into an air-filled swim-bladde r with ossified walls. In the Solnhofen coelacanths we call see the characterist ically pecu liar fin structure with the stout base and brush-like end , which , in Palaeozoic forms. evolved into the limbs of modern land animals. Coccoderma (fig. 7.68) is a small coelacanth with a narrow body and pelvic fin s in an ante ri o r position near to the pectora l fins. It has a promi nent scale cove ring and the vertebra l column is unossified. The weakly ossified swi m-bladde r is seen nea r the fron t of the body, visi bly outli ned by a brown st ain .
REPTLLES
The So lnhofen Platten kalk has yielded a varied selection o f repti les whose ha bit ats were eithe r marine or te rrestrial. The primary classification o f the rept il es is based on t he number and position of the skull openings which allow fo r a bulging of muscles when they are relaxed (see fi g. 7.69).
Turtles (chelonians) rhe turtles are anapsid reptiles (fig. 7.69a). In this group the only skull openings are those o f the eyes, nostrils and brain stem. The most obvious Icature of the turtles is their body armour , consisting o f upper and lowershe lls. rhe uppe r shell is made of an intergrowth of ribs, backbone plates and o ther ma rginal plates, and the lower shell of the lower ri b cage and pa rts o f the , houlder girdle. In modern turt les the she ll is overgrown by a horny substance, which is not preserved in these fossils. In some turtles, includi ng some Solnhofen genera , the armour is lightened by leaving ' windows' between the plates presumably to facilitate swimming. However, the Soln hofen turtles l"illlnot have been true open-sea swimmers (as is the example in fig. 7.70) hCl.:ause instead of fin s they had stumpy toed limbs which were evide ntly ilI .tdapted to swim ming. T hey probably lived partly in freshwate r and partly ulong Ihe sea coast. A ll specimens found so far are , at half a metre in le ngth, ,mall in comparison to today's turtles and may be juveniles. Of the fo ur easily Iccognizable genera from the Solnhofen Plattenkalk Ellrystermun is figured (1Igs. 7 .71 & 7.72). T his genus is cha racterized by a shallow shell wi th narrow,
lilt 7 ~III II ;
(I)
Amiiform , h (l l o' I ~'H n lI'h : Ca ll1l"r/l [ /lrm/tll' Ag.lssiz, Schcrnfcld bci EichfIIlll , IIStJll(,M 1%·1 XX III 1:'i 9
10lat Icnglh 1(-):'1
1
Allimals: vertebrates - reptiles
Fig. 7.65
Drawing of AspidorhYllclms.
,., .'
Fig. 7.66 A~pid\lrhvll..:hitnnn . holm,lea n fish ; Be/OIlOS/OIllIl.... IIlII ells/cri Ag,.ssiz. htllt1t.lcngth 345 111111, B:-i !'1 I(;M 11)~7 I J:W
,"
J
/
Thefossils
Fig. 7.67 Teleost fish; PlIchythrissops propufl/s (Wagner). Pain tcn bci Kclhcim ; to tal Icngth 385 mm; BSPHGM 1964 XII I 154.
Fig.7.68 Crossopterygian fish; Coccotiefllw 1IIIlIIIIII Rei' . Kclhclln: towl length 188 OlIO : IlS I'IiGM 1887 VI ~Ol.
,.,,.
Animals: verteb rates - reptiles
" a
c d Fig. 7.69 Side views of reptilian skulls to show various types of temporal opening. (a) No opening: 'anapsid' condition . (b) A lower opening with postorbital and sq uamosal meering above: 'synapsid' condition . (e) An upper opening with postorbital and -.quamosal meeting below: 'parapsirl' condition. (d) Both openings prescnt : 'diapsid' condition. Abbreviations: j , juglll; pa. parictal ; po, postorbital ; sq, squamosal. From Romer (1962).
Fig. 7.70
Drawing of modcrn sea turtle.
marginal 'windows', The lower shell too shows one central and two lateral
openings.
Ichthyosa urs Ichthyosaurs. as most swimming reptiles (apart from thc turtlcs), are parapsid . They have onc additional skull open ing, high on the head and bordcred on the lowcr <;idc by a lliIT u f hone.: (fig . 7.69c) . Thcy are well adapted for swimming , wi th a ~t rca lllhr1 Clt ,,11111'''' IUld limbs convcrted to fin s (fig. 7.73) . Thcir long
The fO:l'si/s
178
A/limals: vertebrates - reptiles
Fig.7.72
rig. 7.73
Reconstruction o f EllrYSlerllll1ll carapace.
Reconstruction of the ichthyosaur animal.
~ no ut , numerous teeth and large eyes all suggest they were predators of the upen sea. The ve rtebral column dips sharply downwards in the tai l region . This I'; known nol to be a post-mortem feature, because some speci mens from the Lias shales of Holzmaden in so uthe rn Germany are preserved with an ou tl ine u f skin arou nd the downwardly defl ected vertebral column. T he paddle-like paired fin s probably function ed as stabilizers rat her than rudders. A few ~ pccimens from Holzmade n are preserved wit h young inside which , like their l'cologica l descendant , the whale , would be born alive and lai l-firSI into the waler. A hho ugh ichthyosaurs are common in the quarries of Ho lzmaden . such kt rge creatures of the open sea did not ofte n find their way into the Solnhofe n lagoons. Fig. 7.74 shows one of on ly two gene ra known from the Solnhofen Plattenk alk , Macropterygius . It is a partia lly disi ntegrated corpse, the lai l a nd postcrior fins having already falle n away and been lost.
Plesiosaurs I'l e)o in ~ .. urs
were also large. swim ming reptiles well adapted to deeper waters. rhey havc IWO giant pairs of paddles on a rat her plump body. To make room
h~,
7.7 1
runic;
U!'i I' IIGM AS I MIX,
1~-'"I' ftl'rIIlf'''
wag/l'rt
Meycr. Kclhc im ; skull Icngth 66 mm ;
Thefossils
Fig.7.74 Ichthyosaur; M acroplerygills POSIlUIIIIIIS (Wagner). juvenile, Solnhofen ; maximum diameter of eye socket 83 mm ; BSPHGM 1954 I 508. for massive padd le muscles, as well as a protection against water pressure, the shoulder gird le and pelviceicmcnts are widened to enormous bony plates. One of the two types of plesiosaur is known from the Solnhofen Plartenkalk . It probably lived in the open sea and made forays into the lagoon , on one occasion leavi ng behind a tooth. The large size of the tooth , some 23.5 cm in lengt h, suggests the ent ire animal was not less th an 12 m tong.
Lizards (Iacertilians) The lizards and snakes together with the liza rd-like rhynchoceph alians all belong to the Lepidosauria. The lepidosa urs, crocodiles and dinosaurs are all diapsid repti les, characterized by two additional pairs of skull openings (fig. 7.69d). In the lizards, the lower openi ng has lost its lowe r margin and is therefore open below, unlike the rhynchocephalians , which retai n a bar of bone in this posit ion. T he skulls can be compared in fig. 7.75 but unfortunately not all specimens are well enough preserved to permit this discri min ation. On ly a ve ry few Sol nhofen lizards arc known and are assigned here to five genera . Eichstaettisaurus is figured (fig. 7.76) , but it may nOI warrant d istinction al H generic level from Ardeo~'allms which hllS two fewer thoracic ve rtcbrue. On Ardeosallrtls the narrow . upper skull openi ng i\ clcurly \'; ~ , hl l.!, th e vertcbrae
180
Animals: \'ertebrates - reptiles
a Fig.7.75
Skulls of (a) lizard and (b) rhynchocephalian.
lire la rge and strong, and the neck squat. These rather stout lizards may be relatives of the modern sk inks. Their habitat can hardly have lain in the coasta l regions because specimens are fou nd so rarely in the lagoon. Even t he few rhynchocepha lians arc mo re common than these true lizards.
;f''>
·1
,
I·lg,7.76
.
Lizard ; Eid,\'f(lelllfllllrtIHcllrocflcri (Broili) , Wintcrshofbci Eichstiitt; skull
Ic nglh 19 111m ; !lSI'] 10M 11}17 1 1
IRI
The fossils
Rhynchocephalians The beaked lizards fro m the Solnhofen Plattenkalk are of si mila r small size to the true lizards an d the nearest living relative was thought to be Spltenodon, from New Zealand (fig. 1.77). Rhynchocephalia means 'beaked head', which j.., a reference to the shape of the snout. Apart from a few problematic forms the species can be accommodated in two genera; Kallimodotl (fig. 7.78) has a longer and narrower skull than its relative Hom eosaurus (unfig ured), bolh having elonga te skull openings. A small chambe r is often preserved in the apex o f the skull . Kallimodoll was about a quarte r the size of Spizellodoll, with shorter and stouter appendages. The swimmi ng lizards, such as Pleurosaurlls (fig. 7.79) and the smaller Acrosaurus (possibly ajuve nile of Plellrosollrlls), are probably also members of the Rhynchocephalia. Since they all have a beaked skull, elongate body and short legs, the lack of t he lower skull ope ning is probably secondary. The litt lc legs would probably have functio ned o n land but were more o ft en used in the water as stabilizers. With its snake·like form and laterally compressed tai l PleurOS(lllrllS was probably a highly effi cient swimmer in the manner of an eel. T he nasal openings at the top of the head are fairly far back so that the animal needed only to bring its head to just above the water surface in o rde r to
Fig.7.77 Drawing of purported rhynchocep halian from New Zealand Sphello(/oll . approx. length 600 mm.
Fig.7.78 Rhynchoccphnlilln: Kallimmloll Iwlehe/llu (ZlllCI). 1" ll l1tcn !lei Kclhcim, length 175 mm; BSP II GM IRS7 V12.
182
Animols: vertebrates - reptiles
J
I
.
'. '111
I R1
Th e fossils
Fig. 7.79
Rh ynchocephalian; Pleurosallrus gold/llss; Meyer , Sappenfeld bel Eich·
statt ; length 1520 mm ; BSPHGM 1925 11 8. breathe. It also bore six-sided sca les. Plellrosallrlls is found most frequently where there is an accumu lat ion of driftwood which suggests that it lived in a stream and its dead body was washed into the lagoon.
Crocodiles Crocodiles are also diapsid repti les. All the Sol nhofen specimens have an inner nasa l open ing which is not shifted as far back as it is in the modern crocod il es. There are three types of Solnhofen crocodile . The fi rst , exemplified by Alligalorellus (fig. 7.80), is a sma ll crocodile by modern standards at on ly 50 Clll long, and much of the body is covered by an armour of bony phllcs. T he long limbs enabled the animal to hunl on land as well as in the watcr. As is the case for all land animals, the Solnhofen Plattenka lk has yiclded few specimens and they have all come from the Eichstiitt and Kelheilll regions. The second type are coastal crocodiles, but Ihes!; nrc ex tremely rarc. A reconstructed specimen of SUmCOS(lflrtl$ . some 4 In In lenglh . i~ on di<;play in 4
Allimals: vertebrlltes - reptiles
hg.7.80 Crocodile; Afligaroreflus beaumomi Gervais, EichsHitt ; length 305 mm ; US PHGM 1937 126.
the Jura-Museum in Eichslalt. Its long sk ull suggests that it preyed on fish. It has paddle-like limbs, one of which has a membra ne still preserved between the toes. The back and unde rside were covered by protective bony plates and the fla nks probably bore a scaly skin. The single specimen of A eolodon ( now missing), which was described from the Dailing plattenkalk , may also belo ng to this gen us. The last group of crocodi les is of such different construction that many workers would place it in a sepa rate suborder. GeosQlIrllS is a small e legant fo rm of around 2 m in length. The limbs are modified to fi ns and the bo ny urmour plating has been abandoned to fac ilitate movement through the wate r. A vertical tail fin and a fi ne ridge alo ng the underneath and back of the animal were also new developments. The skull is lightly built and in the narrow jaws are set small teeth of equal size. Similar sets of teeth in other groups are usually u ha llmark of life spent hunting in the open sell.
'Oinosaurs' The te rm dinosaur was invented to include all the giant land repti les and is ge ne rally regarded li S un Ulullltural grouping. There are two groups, the Suurischia and the Ornithhchia . which diffe r in the construction of the pelvi s.
The fossils
,
.... Fig. 7.81 Dinosaur; COf1wsog//{II/IIIS lOl/gipes Wagncr. Jachcllhauscn bei Kelhcim. width of picture c. 315 mm ; BSPI-IGM AS I 563. Not all the dinosaurs were gigan tic in sizc. Compsogllothus (fi gs 7.81.7 .82 ~~ 7.83) , which is the on ly dinosaur found in the Solnhofen Platle nkalk ami represented by on ly this one speci me n . is scarce ly bigger than a c hickclI Compsogll(ltllll,f is a coclurosll urian dinosaur. which h jhelr a suhgroup of t h(.' Theropod'l. ,In(l thus ,I memher o f the Sa un<;chia III\h(.' light und T\)hu,t ,ku ll
Allimals: vertebriltes - reptiles
Fig. 7.82
Reconstruction of CompsoglliltJws.
I lg. 7.83 Drawing of small lizard in the gut of Compsoglluthus. there are two open ings beh ind the eye holes and another between the eye and the nostrils. CompsogllGthus has a lo ng, forward-leaning body coun terbalarH.:cd by a thick tail. The two, strong, long hind legs, used for running, terminate in five toes. The fo re limbs arc short with two-fi ngered hands well ,tdapted to grippi ng prey. On a long narrow neck, a small pointed head could be ,wivelled in search of prey. The jaws have the pointed, slightly backwards n lrving teeth suited to hold ing and gorging food. In th is specimen, a small ,k eleton is preserved in the stomach. Th is was firs t thought to be an embryo, hu t then recognized as a sma ll ground lizard , evidently the diet of CompsoJ.l1I(1I11II.~ (Ostrom 1978). T he supposed tracks of Compsogll mhlls fro m the Solnhofen Plattenkalk have since been recogn ized as li mulid traces.
Ptcrosaurs I here have bee n three groups orvertebrat cs which have at various times taken til activc fli ght. In Latc Jura"'lc tllllC!, bird ~ were at the very beginning or their development. FIYlIllt Illilmmuh , Indudinl-: Ihe hal\ , did not evolve until T crI ",
,
\
The fM$ifs
tiary times and it was the pterosaurs, winged relatives of the di nosaurs, who at this time reigned supreme. In Solnhofen times the pterosaurs , with wingspans averaging I m, were small by comparison with the giants of the Cretaceous who sometimes achieved wingspans of 15 m. Pterosaurs have skeletons which are strongly, yet lightly built. On the forelimb , the fourth finger is very long and from its tip st retched the wi ng membrane which at its other end was attached to the body. The first three fingers articu lated separately and were used for grasping, the fifth being lost in the course of development. In the extremely well-preserved Soln hofen specimens, hair-l ike structures may sometimes be seen on the wing membrane. In mammals a hairy coveri ng is used to conserve in ternally generated heat, and if the 'hairs' of the pterosaurs had a simi lar role , it implies the pterosaurs, too, were warm-blooded. Some pterosaurs may have been partly aquatic in their habits. T his is adjudged both from the webbing between their hind toes and from the stomach contents , which include fis h. In Jurassic genera , the teeth are small and numerous and would also be well adapted for a diet of insects. Of the two groups of ptc rosaurs. one incl udes RhampllOrhYIlc!ws (figs. 7.84,7.85 & 7.86). This has a powerful, large sk ull with strong, forward-poin ti ng teeth and a horny coati ng on its long snout. The most conspicuous fea ture is the long, rod-like tail wit h an upright rhombic-shaped vane at the end. The tail is strengthened by a process originat ing from two fused vertebrae. In Pterodacly/u s (fig. 7.87). the bones in the middle of the hand are considerably lo nger. The teeth are short and conical or else long and delicate. T he very si milar Ctellochasma (figs. 7.88 & 7.89) has an even finer array of small teeth, probably used fo r seizing small an imals out of the water or for catching insects .
.,
"
-.,
'.,
Fig. 7.85 Wing of Rlwmpho rhyf/ cllll.l' /11l/ t'II.lIeri (Ciuldfu,,), W inl c l', hof!lei Eidl ' llit! , Ic ngth of wing bonc 38-1 111111 : R$ PI IGM A S 1 77 1.
,0
Animals: vertebrates - birds
\. .. '
..
Fig. 7.86 Reconstruction of RhamphorhYllchus.
BIRDS
Archaeopteryx ·r he historical context of the discovery of A rchaeopteryx is dealt with in chapter I. pp. 10- 15. Remarks on the mode of life arc incorporated in chapter 5, pp. R4-8, and burial in chapte r 6, pp. 93-6. See also figs. 7 .90--7.95. The const ruction oftheArchaeQpteryxskeleton is d istinctly reptilia n but with a fe w outstanding avian characteristics. About the size of a small chicken , it had long legs and a bony lail. The sku ll is quite primitive with theeyes still protected hy bony plates and the jaws bearing teeth. Archaeopteryx did not have a kee led extension to its stern um , nor the fork-l ike terminations (uncinate processes) to the ribs which , in modern birds, serve for the attach men t of fli ght muscles. Conversely , Archaeopteryx retained the abdominal ribs (gastralia) wh ich modern birds have lost. T he pelvis is typical ly reptilian except for the (act that lhe pubis probably pointed backwards. In the backbone, all the vertebrae are w ncave at both ends, and freely movable rather tha n fused. The vertebral culumn rewi ned the long repti lian lail , a feat ure not shared with any living bird wlu.:re the t:,il is reduced to a sho rt bony stump but may be covered in lo ng fca thers. Three fin ge rs on the hand are no t incorpora ted into the wings and are Irccly mova ble as clawS.
Thefossils
Fig. 7.87 Pterosaur; BSPHGM 1937 1 18.
192
1)lero(I(lcl)'/lJ~ koclli
(Wagner), Eichstiitt; length of sk ull 83 mill ,
Allimals: I'lmebrates -
bird.~
lig. 7.88 Ptcrosaur; Ctelloclltlsma gracile O ppel. Willtcrshof; skull length 104 mm ; IIS PH G M 1935 I 24.
193
Allimals: vertebrales -
bird.~
1 9~
Thefossils
Fig.7.92 Delail of Ihe skull of Archaeopteryx filhographica Meyer; Eichsliitt speci· men, Workerszell bei Eichstiitt ; skull length 39 mm ; JME .
On previous pages
Fig.7.90 Specimens of the bird , Archaeopteryx. and map of their original loca lilie:.. Adapted from Wellnhofer (1974, 1988b). Fig. 7.91 Arclmcopteryx lithographica Meyer; Eichstiitt specimen, Workcrslcll hel Eichsliitt; skull length 39 mOl ; JM E. Copyright of tlUlt col lcCl iuu. Phologruph by p , Wclln hofe r.
196
Allimals: vertebrates - birds
However, all the Archaeopteryx specimens have feathers, feathers in fact so well developed that they are indistinguishable in fo rm and distribu tion from t he fligh t feathers of modern birds (d iscussed in greater detail o n pp. 86-8). Feathers are clearly derived from repti lian scales but no repti le has feathe rs and It is on this one, critica l feature that Archaeopteryx merits classifi cation as a true bird. Severa l othe r avian characteristics have bee n attributed to Archaeopteryx. Individually each characteristic has been challenged , but the collective presence of these avian features must be more tha n fortuitous. One of the most co mmonly cited avian features of Archaeopteryx is the structure of the fOOl ; the li rst toe opposes the other th ree, a feature thought to be used in perching and ;:111 exclusively avian cha racter. Now, however, this feature has also bee n found III other dinosau rs. The backwardly directed pubis is also an avian fe ature but III Archaeopteryx there is debate as to whether it is origina l or simply due to com paction. All birds have the co llar bones (clavicles) fused together into the wishbone (furcula) which prevents the chest collapsing unde r vigorous moveme nt of the arms. The London specimen certainl y does show a massive wishbone (which incidenta lly is detached and upside-down wi th respect to the rest of the skeleton) , but a wishbone is not visible in either the Berlin or Eichstatt specimens. T here have bee n reports that Archaeopteryx also had airli lled cavities in the bones, as do modern birds, but this is now no longer thought to be the case. The six speci mens of Archaeopteryx diffe r from each o ther in various respects, besides the obvious d iUerences in preserva tion. Of thc e nt ire (or al most entire) specimens, the Eichstatt specimen di ffers from the o ther three the Berlin, London and Soln hofen speci mens. The Eichstatt specime n is about two-th irds the size of the Berlin and London specime ns and half the size o f the Solnhofen. Its teeth arc also d isti nctively differe nt (Howgate 1984a , b). They Me narrow , conical and curve backwa rds, wh ilst those of the London and Berl in specimens are stouter and more peg- like. In the Eichstatt specime n the teelh interd igitated (as is probably the case also in the Be rlin specime n , judging Irom the wear facets), whilst the London speci men had teeth which ea me iogcther (occluded) when the jaw was closed. The differences mllst be related to .. difference in diet. In addition, in the Eichstatt specimen the sho ulder is l)(Iorly ossified (Welln hofer 1974) and also differs in having longer hind limbs. II may be that the Eichstatt specimen should be a new species or even genus, or !!ItH ply that it is a juvenile. Indeed , the Berl in specimen was originally assigned 10 a new ge nus but at present time the name generally used for a ll seven ~rcci m e n s (i.e. including the feather) is Archaeopteryx lithographicfl von Meyer.
hM· 7.94 Archaeopteryx fithogmphicli Meyer ; Solnhofen specimen, Eichslatt area?; kngth from fOOl to restored end of tail 395 mm. Photograph by P. Wellnhofer.
I 1M 7,93 (OPI>osil C !,lIge) Arr hm'OI}/l'ryr litlrogrllphica Meyer; Be rlin speci men , BluI1fl'nhcrg hci Eiclhtil tl ; ICIIj.\lh of ' kill! ~2 111m ; PAMN II UB MB 1880181.4598, cou n tc rJlilll " 'it}!)
,00
The fossils
Fig. 7.95 Rcconstructionor Arclweoplt'ryx based on the model in the British Museum or Natural History.
?flO
Allimals: vertebrates - birds
Fig. 7.96 Archaeopteryx /itllOgraphica Meyer; the isolated feat her. BSPHGM .
2111
8
Conclusions: The Solnhofen Plattenkalk and comparisons to other plattenkalk lagerstatten Summary of the characteristics of the Solnhofen Plattenkalk
The Solnhofen Pl attenkalk contains the bodies of both marine and terrestria l
organisms and must have bee n deposited in a shallow sea. This water was protected from ocean turbulence by an outer barrier of coral reef, and water movement was further restricted by the dead sponge- algal mounds which subdivided the Platten kalk lagoon into sma ller basins. Pulses of fine marine sediment rained down through the quiet waters to the bottom o rlhe basins and these sed iments now form the Hat sheets of Plattenkalk rock. There are tWO lithologies: pure homogeneous limestone beds, varying in thickness from (typically) 1 to 30 em , separa ted from each other by thinner beds of argill aceous limestone wh ich range in thickness from th in laminae to beds 1-3 Clll thick. Chemically, the limestone beds are al most pure calcium carbonate , wi th a low concen tration of organic matter which gives the th ickest beds a bluc-grey colour when freshly broken. The limestone beds may be fin ely laminated on a millimetric scale, but do not usually cleave along these planes. When a limestone slab is removcd from the section it shows distinct upper and lower surface textures, and the fossi ls occur almost exclusively on the underside of a slab. Fossils are hard to find in the Sol nhofen Platten kalk and a day's coll ect ing may produce nothing. Only from the established collections is it possible to compare the relative abundances of different sections o f the fauna and flora although we must bear in mind that only the best preserved and most showy of specimens may be on display; poorly preserved specimens are too oftcl! disca rded, even though they may be a valuable source of info rmation. In Ihe assemblage of marine fossils there are main ly planktonic and small nektonic organisms. Benthos is under-represented . Presumably this is because. in contrast to the inhabitants of the surface waters. they were less likely to he swept away from their normal ha bitats into the Plattenkalk basins. Most of the an im als died as soon as they were plu nged into the Plattenkalk waters so they had no opportunity to make t racc fossil s. The only trace fossils whi ch :Irl' presen t can be att ributed to species whose livi ng relati ves urc pa rticularly resistant to extremes in si,l inity or temperaturc. The he~ t known o f Ihese is the
OIlier plrlllellkulks
horse-shoe crab , Mesolimll/IIS. which crawled disorientatedly in a spira l over the sediment before it succumbed to the hostile cond itions. The bod ies of tcrrestrial organisms also came to be buried in the Plattenkalk sediment. These mcl ude a large and d iverse collection offtying insects as well as reptiles, such as ptcrosaurs and lizards, and that most celebrated bird, Arcliaeolneryx.
Other plattenkalks with exceptionally preserved fossils Of the other plattenkalks which show special preservation, the nearest deposit In Solnhofen , both in ti me and space, is at Nusplingen in the adjacent Swabian Alb (e .g. Temmler 1966). Th is plattenka lk is slight ly younge r, being KimmerIdgian in age . and in a very simila r geological setting. The Nusplingen platte nkalk was also laid down in a hollow between sponge- algal mounds on a hroad shelf, but the sides of the Nusplingen basin were probably slightly , teeper than is gene rall y the case for the Solnhofen area. Piles of sedime nt regularly collapsed downslope depositing slump beds and turbidites. T he re are illso coarse breccia beds in the sequence , which represent mate rial eroded from the sides o f the sponge mou nds. Lithologically , the Nusplingen plattenka lk is lh ffcrent from that o f Sol nhofen. There is no eq uivalent of the thick, pure homogenous limestone beds nor of the intervening marls. The beds are equally Impure (about 10% insoluble residue) a nd cleave on a millimetric scale along mternal laminations. The Nuspli ngen plattenkalk also lacks the regular fine~ra in cd constitu tion of the Solnho fen limestone slabs which make them ,> wluble for lithography; there is more coarse de tritus, sponge spi cules and a cll lour banding due to varying concentrations of organic matter. The distinct ive '>urfa ce textures of the Solnhofen slabs a re nOI present (perhaps, as suggested hy I Hickel 1970, because marly part ings do not separate the limestone beds), und the fossils are not restricted to the underside of limesto ne slabs. However . thc collection of fossil s is similar in conte nt to those from Solnho fen in so far as thcre ; Ire the bodies of both marine and terrestrial organisms, and in the marine cullcction nekton and plankton predominate . Spiral death marches are , howevc r, not known from Nusplingen . Many of these fossi ls are also superbly prc~e rved and provide fu rther insigh ts into L.:"l te Jurassic life . A lt hough frequent ly compared to the Solnhofen Plattenkalk , when exa mIIIC(l closely , the plattenkalk of Sierra de Montsech (e.g. Barale et at. 1984) lIum the Mesozoic sequences o n the sout hern flanks of the Pyrenees is Itt hulogicall y qui te (l issimilllr. Its ilge is Ea rly Cretaceous (Be rriasianV" IHngini an) , M) it is younge r than the Soln hofe n deposit. It must have been la td down in a broadly similar , lagoon -type setting. However, th is lagoon "rollithly lay ve ry clo'>e to the C(l w,1 and , although the plattenkalk itself shows 110 ,t ruClurc, IIldl CitllV I' o f ~· t1t(· r~C Il CC. other units of this sequence are intcr- or ? f)1
ConclusiOlls
supra-tidal. There are stumps in the sequence denoting a slight slope and implying that the plattenkalk was deposited in some kind of protected basinal area. The Montsech plattenkalk is similar to the Soln hofen in that it is a finely laminated limestone but here the lithological comparison ends. Instead of a homogeneous fine-grained texture , the beds are rhythmically layered wit h horizons of ostracods and other bioclastic debris and pieces of torn alga l mat. The plattenkalk may be quite impure, generally reddish-purple in colou r and somet imes colour ba nded due to differences in clay, iron oxide and organic conten t. As at Solnhofen , the beds themselves are a few centimetres in thickness and do not cleave internally . The fossi ls are no t located exclusively on the underside of limestone beds , but split evenly between the under- and overlying slabs. In most respects the collection of fossils preserved in the Montsech plattenkalk is quite different from the Solnhofen assemblage. Although the fish are most numerous (includ ing some sha rk eggs), in Sierra de Montsech many genera are endemic and were probably brackish water in habitants. The rc are also amphibians, bird remains, many insect and some spider fossils, a nd large, well-preserved pieces of plants. Unlike Solnhofen most of these animals lived in the depositional basin in conditions which were probably quite equitable, and there are trace fossils including coprolites. Another important plattenkalk outcrops in the south of France, in the southernmost parts of the French Jura mountains. near to the small village of Ceri n (e.g. Enay & Hess 1970. Gall & Blot 1980). The Ceri n plattenkalk , being Kimmeridgian , is rough ly comparable in age to the Soln hofen and is also in a back-reef position . The Cerin beds are not dissim ilar in colour or text ure to those of Solnhofen. In thickness, entire beds do not reach the 30 cm achieved at Solnhofen , but the bedding on a scale of 0.5-10 cm is roughly com parabl e. The limestone beds are separated by fine marly partings and certainly in the lower part of the sequence there is an internal lamination. The surface of the beds is slightly undulose and some are covered by a pattern suggestive of the erosion of a thin algal mat (G all etal. 1985). This feature , together with the celebrated reptile tracks which adorn some bedding planes and the predominance of small burrows in the upper part of the thicker slabs, suggest episodic sedimentation interrupted by periods of elllersion (or at any rate very shallow water). Fossils are usuall y found on bedding planes although they do not preferentially adhere to the upper surface as is the case at Solnhofen. The assemblage is representative of a littoral environment and is do minated by fi sh, reefal and benthic form s being much commone r than trul y pelagic variet ies. Invertebrates are less common , although theircoprclites and faecal pellets may be quite abundant. The terrestrial reptile fossils (rhynchocephalians, tortoises , crocodiles and pterosaurs) are also an important part of the Cerin collections . The four examples given above - Solnhofen , Nusplingen. Sie rra de Mont sech and Ccrin - arc all plattenkalks deposited in a brondly IHgooni.II se tting. However, plattenkalk wi ll form in other gcographicll i ~c llin g .. gIven the
Other plauenkalks
prerequisite of a protected basin and periodic supply of lime mud. For example , there are also shallow~water deposits wh ich are not associated with reefs, such as depressions in shelves of tectonic origin (e.g. Bear Gulch plattenkalk of Central Montana, USA ; Williams 1983) , or t he plattenkalks of Ilaquel and Hjoula in Lebanon (Huckel 1970). The latter is also an example of ,I plattenkalk deposited under water too deep for benthic microbial/algal mats and the sediment is mostly pelagic. There are also plattenkalks which have fo rmed in lakes , such as the Green River plattenkalks of Colorado, Wyoming and Utah (e.g. Bradley 1931 , 1964). All the examples given here are p l atten ~ kalks wh ich con tain an exceptionally preserved fa una and flora. For an expanded discussion of plattenkalk deposition the reader is referred to the review article by Hemleben & Swinburne (i n press). T hus, to conclude, the Soln hofen Plattenkalk is one of the most celebrated examples of exceptional preservatio n in the foss il record. It is a la ndmark in the history of life and its classic stat us confers an importance and re levance to all who seek to understa nd the gene ral problems of evolution. A nd yet it is only one of a number of plattenkalks, most of wh ich yield some well~preserved fossils, although none approach the diversity and richness of Solnhofen. These lIcposits show significant featu res , but each also has uniq ue characters and owes its overall nat ure to special combinat ions of geology and palaeoenviro nment. T he Solnhofen Plattenkalk owes much o f its foss il fa me to the conti nuing quarryi ng and the sharp eyes of generations of Bavarian workmen. Without A rchaeopteryx, the celebrated death marches of doomed limul ids, and the exquisi tely preserved fl ying reptiles and fish , palaeontology and evolutionary hiology would be much impove rished . T he Solnhofen Platten kalk is a unique deposit , but it is evident t hat a greater investment in to systematic and scie ntific cxcllvations of plattenkalks (and othe r typesof lagerstiitte) wi ll open new vistas mlO the va nished worlds of the past.
•
Appendix Faunal and floral list
The macrofossil list is derived directly from Barthel 's book with only minor corrections and addit ions, and so many names may already be out of date. The microfossils come from two additional sources: the entire list of foraminifera from Groiss (1967) and the calcareous nan nopla nkton from Keupp (1977).
Monerans Cyanobacteria
Protists Coccolithophor ids Bidiscus bellis (Noel) Bidiscus ignofus (Gorka)
Biseulwn ellipticllm (Gorka) Cyc/age/osphaera margereli Noel ElfipsagelosplJaem britannica (Strandne r) EllipsageiosplJaera keftalrempti Grli n Ellipsagelosphaera OIlOW (Bukry) Microstaurus a/ell/one"s;s Keu pp Podorhabdus cylil/dratus Noel Podorhabdus dietzmanlli (Reinhard t) Slaurorhabdus quadriarcullus (Noet) Stephanolithion bigoti Deflandre Watznaueria bamesae (B lack) Watzllulleria deflandrei (Noel) Zellgrhabdot/ls noeli Rood , Hay & Barnard Zellgrhabdotlls snlillllm (Noel) ?Loxolitlllls sp. ?Tetmlitl1l.lS py ramidlls Garde t ?
,
Faunal and floral list
Calcareous nannoplankton of uncertain systematic position Pselldolithl'llphidites multibacillmus Keu pp Pseudolithraphidites quattl/orbacil/atus Keupp Calcispheres Pithonellll gustafson; Bolli Pithonella cf. thayeri Bolli Pithonella piriformis Keupp f'ora miniferans Gaudryina bukowiensis C ushman & O lazewski Marginu/imj distorta Kusnetzowa Nodosaria euglypha Schwager Patellina feifeli ( Paalzow) Quinque/oculillo egmonfetlsis Lloyd R1'I dioiaria indet,
Plants Non-vascular plants I'haeophyles, brown algae Phyllotllllllus
Vascul ar plants (;ym nosper ms I)teridospe rms Cycadopreris Bennettitales Sphellolamites Zmnites Ginkgos Baiera (someti mes known as Furci!o/ium) Gi"kgo Conifers ArtlllCllriO
ArrhrOUIt/rl!l' (prevo Edlillostrolms) IJr{/chVfI" yll /I'" POf(Il'Of 1'//(11/ \
Appendix
Animals Invertebrates Sponges
Ammonella Tremadictyon Cnidarians
Scyphozoans, jellyfish Cannostomites Epiphyllina Eulithota Leptobrachites Quadrimedusina Rhizostomites (includes Myogramma , Hexarhizites & Ephyropsites) Semaeostomites Hydrozoans Acalepha Acraspedites Hydrocraspedota Anthozoans, corals 'Iridogorgo nia' Annelids
Ctenoscolex Eunicites Serpula Bryozoans Brachiopods
Lacuflosella Loboidothyris Septa/iphoria Molluscs
Bivalves Arcomytilus H/lchia (prev. Aucellf/) EOI)eCleli
208
FauI/al and floral list
Inoceramus Liostrea Pinna Solemya
Gastropods Ditremaria Globularia ' Patella' Rissoa Spinigera Cephalopods Squids & cUlllefish Acal1lhoteuthis Celaenoteuthis Geopeltis Kelaeno Leptoteuthis Palaeololigo Plesioteuthis Trachyteutlris ...cc also Engeser & Reitner (1981) & Engeser (1986) Belem nites Duvalia Hibolites Raphibelus (possibly a juvenile of Duvalia) Nauti loids Pseudaganides Ammonites Aspidoceras Glochiceros lithographicum (Oppel) • Glochiceras solenoides (Quenstedt) Gravesia Hybonoticeros Irybonotum (Oppel) Lithacoceras Neochetoceras steraspis (Oppel) Subplanites Sumeria Taramellict!rQS prolithographicum (Fontannes)
Appelldix
Arthropods
Crustaceans Malacostracans Mysidaceaos Elder Frallcocaris Isopods Palaega Urda Decapods Natantians Acanllzochirana Aeger Amrimpos B1aculla Bombllr Bylgia Drobna Dusa He/riga Raul/a Udora Udorella Replantians Cancrinos CycleryolJ Eryma Eryoll Ell/llonia Glyphaea Knebe{ja Magila Mecochirus NodoprosOpOfl Palaeopeillacheles PalaeolJOlycheles Pa/inurina (and juveni le prevo Phyllosoll/a) PselldastaClis Sfelloclliru.f Slomalopods SClllda
210
Faunal alld floral list
Cruslaceans of unknown affinity Allihollema Uuvenile crustacean) Pfllpipes Uuvenile crustacean) Ostracods Cirri pedes, barnacles A rellaeolepas Brachyzap/es (trace fossil)
Chelicerates Xiphosurans Mesolimllius
Arachnids Siernarlitron
Insects Ephemopterans, mayflies Hexageniles
Odonatans , dragonflies
•
Aeschnidillm Aescilnogomphlls Anisophlebia £Ilphaeopsis Isophlebia Ube/llllillln (prev. Cymarophlebia) NamlOgomphus PrOlolindenia Pselldoellphaea Sieleopteron Stellophlebia Tarsophlebill UrogomplllIs
Blattoideans, cockroaches Uthoblatta Megalocerca Progeotrupes
Phasmidans, water skaters Chresmoda En~ifcrans,
locusts & crickets
. £IClllIll' JI/muo/mlca
PYlfIOP" It'I'/11 21 1
Appendix
Heteropterans, bugs & water scorpions Mesobelostomum Mesocorixa Mesonepa NOlonectiles Sphaerodemopsis 'Auchenorryhnchans', cicadas Archepsyche Eocicada Limacodites Prolopsyche Neuropterans, lacewings Archegeles Kalligramma Mesochrysopa Osmylites Coleopterans, beetles Actaea Amarodes Apiaria Cerambycinus Curculionites Eurthyreites Hydrophilus Malmelater No tocupes Omma O ryctites Procalosoma Pseudohydrophillls Pseudothyrea Hymenopterans, bees & wasps Pselldosirex Trichopterans, caddis fli es A rchotalllius MesolalllillS Dipterans, fli es Empjdia ProhirmOfleura see updated review in Ponomarenko (1985)
212
Fauna/ alld (lora/list
Echinoderms Crinoids, sea·lilics Miller;crinus Pterocoma (prev. Amedon) Saccocoma Sofaflocrinites Asteroids, starfish UthaSler Pentaster;a sec also Hess ( 1986) Ophiuroids , brittle slars Geocoma Oplliopsammlls (prev. Ophioctell) Ophillreifa Echinoids, sea-urchins Colfyropsis Hemicidaris Peditw Plrymoped;fla Plegiocidaris Pselldodiadema Rlwbdocidaris Tetragramma Holothurians, sea-cucumbers Acltistrum EocQudina Hemisplraerallllros Priscopedmus Proto/lOlotllll ria Pselldocaudillll Th ee/ia Trace rossils Lllmbricaria illlestiflllm Lumbricaria recta
Appendix
Vertebrates Fish Chondrich thyes Seiach ians , sharks Go/ells (prev. Prisrillrus) Hererodolltus (prev. Paracesrracion) Hexanc!ws (prev. Noridll/lus) Hybodus Orectolobus (prev. Palaeocrossorhinus & Crossorhillus) Pa/aeocarcharias Pa/aeoscyllium PhorcYllis Protospillax (= Belenlllobatis) Pseudorhilla (prev. Squatina) Batoideans, rays Aellopos (prev. Spath obatis) A sterodermus Ch imaeri forms, rattish Chimaeropsis Ischyodus Osteichthyes, bony fish
Acti nopterygii , ray-fi nned fish Chondrosteans, cartilaginous ganoid fis h Coccolepis Holostea ns, bony ganoid fi sh Sem ionotiformes Heterostrophus Lepidotes Pycnodontiformes Eomesodoll Gyrodus Gyronchlls (prcv. Mesodoll ) MeslIIrus Proscinetes (prev. Microdoll ) Am iiformes Asthenocormus Callopterus CmuYlls Clilums (S,robilOlllls) 214
Fa/mal ami floral list
Eurycormus Eusemius Furo (prev. Eugnathlls & Isopholis) Histionows f1ypsocormus I OIlOSCOP"s LiOllesmus Macrosemius Notagogus Ophiopsis Orthocormus Propter/IS Sauropsis Urocles (prev. Megalurus)
Aspidorhynchi fo rmes AspitlorhYllchus 8 elol/ osrom us
Phol idophoriformes O/igopleflr/IS Pholidophorus Pleuropholis
Teleosts, modern bony fi sh Allothrissops A lI(lethalioll Ascalabos Leptolep ides Orthogonikleithrus Pachythrissops Tllflrsis Tlrrissops -,ca also Nybelin (1974) & Arralia (1988)
C rossopterygii, lobe-finned fis h Coccoderma J-/oIOI)haglls (prev. UlIdina) Libys
Kcptilcs Chclonians. turt les Elirystemlwl Itliochely.f P/(l/ycht!ly\ PfI'\;of"lll'l\'\"
215
Appendix
Ichylhyosaurs Leptopterygills Macroprerygius
Plesiosaurs SlretosaurllS (one tooth)
Lacertilians , lizards ArdeosaurIIS BavarisaurllS Eic!lslaettisau rlts Palaeo/acer/a Proaigia/osalt rIIS
Rhynchocephalians AcrOSllUrlIS f!omeosaurus Kallimodon Piocormus Plellrosallrlls
Crocodiles Aeolodon Alligmorel/us AlligalOrium Aloposallrus Dacosallrlls Geosaurus Stelleosaurus
Sa urischian dinosaurs Compsogllathlls
Plerosaurs Aflllrogllalhlls Ctenoclrasma GermanodaclY!us G"alhosaurus PlerodacrylIlS Rlwmphorhy"chus SCa f)hognathus
Uirds Archaeopteryx
216
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Systematic index r hl~ Index lisls both SCicOllfic8nd common names used In the hook down 10 genus level. The main ,k<.eriptionsof the fossils will be found in the page references between [02 and 201 (i.e. Chapter7):
Ihe rest of the page references deal with other aspects of the fossils' occurrences, way of life. Im':'lC rValion. etc. The Appendix (faunal and noral hst) is lIolmdcxcd . IIlUlilrahons are indicated hy Italic page numbers: both the gene ra and largc::r groups are indexed for the figures nOI in Chapler while those III Chapler 7 arc JUSt Indexed by the genus.
II/millo/euriris \rro.wllfUS
124
182
M.tmoplcrygians (su fish. myfinned) 1I·.~t'r
131. J3J
Idlopos
165. 166
!<'fJJedon 185 •• Igac (Stf also
cyMobaclcria)
32.33.
42,76.79,82.83.204 hl\JI:-grccn (su
cyanobaClcria)
hmw"
78. 103.
J(J.I
tlltf.:Mortdlus 184.185 Immomdlo 112
.ulUnonilCS 2.32.32.33. 34. ~7. 63. 67. 68. 76. 84. 89. 92.93.96-9.97.98. 100. 120. 126-9. 135 .lml)lnnians 173. 2Q4 .ulUnals 112-201 Itr"opilltbio 144.145 ,nmchds 117 ,ullho7,oa ns (Sf'<" oorals) ,lIillh mds 141 Irtwnlrill I/O. III ITI/"lI.'oltpOS 135.140.141 '''-/J/ltOfl/tfYX 2. 10-15.84. M-R. 93.100. 191-201, /94-201 \T(/II.'I'S)'(III' 149 ,,,hOI/JUlius 152 tTHlIIII'II/US
[2()
In!t'(}\JJJJrJu 180 '1I1hwpod s 129-52 Irlhro/O.W('I 110. 1[I "1',./tH'rrl., 67.127.129 1I/1II/"rI'\'III;hll) 91, 171. 17l
Hail'm 107 barnac[cs 76. 135 baloideans (su rays) 165 Ocet[es 149 belemnucs 71,76.84,90,91. 100. 120. 123-4. 114. 135 HtlollOSlOlIIlU 91. 17 1. 175 Benncuitales 107 birds 11-1 3.56,86-8, 187. 191-201. 204 bivalves 37.47.76.79.81. 82.82.89. 100. 119-20 Blattoidea (su cockroaches) brachiopods 82,89.118- 19 Brachypll),lIllm
72.] 10-1 1.
//0 HTm:hylapfes 135 brittle Stars (set' ophi uroi ds) bryozoans 79. 103, 117- 18 Bucllia 120 bugs 146--9
caddis flies 152 CQtrcritrOS 13].137 CQ/MUS n. 84, 170, 172 ce ph alopods 74.76.84,90. 121-9 dibranchiatc 121-4 tClrabranchiatc 124-9 CtrQmb),citrUS 149.151 cheliceratcs 78.80,135-41 chc[onians (su lu rl[es) chim ae rifo rm es 1M Chond richthyes (Stl' fish. shark·[ike cartilaginous) Cholldrilts
50
.• ,1<'I<)I(J\ (II"I" 'IIlrfish)
chondrosteans (su fish. cartilaginous gaooid) Ci'"SlIIod(l 144.146
. i\udlcnurl)'hnch:m,' fut
C1ClId,IS
l ll· ••
],.'l
1IIIIpc.lc~
144,)
(\ .... I>;l\I\I\cles)
112-17
c nidarians
CoccQ(lrrmo [73.176 Coccolrpis 167
coceolithophorids (su /llso coccoliths) 42.63.64, 68,70.74. 103 eocco[iths (srI' also COCCOlith ophorids) 33-6. 37. 42.44.46.47. 48,49, 49.51.55.67.74 cock roaches 144 coclacanths 173 Co[copte ra (su Ocelles) ColI,.ropsis 159 COlllpSOgllUlllIIS 12. [3. 14. 86.186-7.186.187
coniferopsids (su oonirers) con ifers 72.86, 108- 11 corals 32-4.56-7.79.82. 81-4, 115-- 17 crabs 58,79.203 cricke ts [46 crinoids 2.74,76.84.89.90.
1S3 crocodiles 84.90. 184-5.204 crossop lc ryg(:ms (su fish. lobe-fin ned) crustaceans 2.58.82.83. &.S. 89, 129-35. 165 CtrrrochQsIIIQ 86. 190. 193 Ct~"osrolr~
cuiliefish
m
82. 11 7.118
74.84.89.1 21-3.
cyanobacterill 26-32.4$.467. 018. 49. 55, 57.58.64-5.
68-9.73. 102 cycadophytcs 86 C,.t:adop/~'is
72.86. 106. 106
cycads 107 Cyd/l/f,l'IQ)plwl'rll
34.44. <Wi •
14
231
Systematic index
CYc/"'YOIl
131.136
deeapods 129--32 dinoflagellates 46. 64 dinosaurs 12.13,14.86, 185-7.197 Diplera (J'ee flics) dragonflies 143-4 echinoderms 47,75,10 1, 153-(,1) echinoids 83. 155-9 cidaroid 157 irregular 82. 159 regular 82. 156-7 EichSlaellisuurus 180.181 'Elcanu' 146 Ellipsagelosplwera 44.46 Ensifera (see locum) £Op~II''' 120 Ephcme roptcra (set' mayflies) Ell11iciles 117 EurySll'rI1l1m 173.178. 179
105,107 'Fisch/finz' 92.94-5 fish 2.42.75.76.77,83-4. 89.90.91. 92. 99. 160-73.
ginkgos 86. 107-8 G/obufari(J 120 G/ochiuTUS 127. 129, IJI
gorgonians 82. 116-17.116, 117 Gfllvl!sia 127 gymnosperms 86. 105, 106-II GyrodllS 42, 167.171 GyrO/lehus 84.167.170
Heteroptera (see bugs) Hexagcnill!S 143. 143 Hiboliles 124. /25 Hisliol/olUs 171./74 holoccphalians (see ratlish) holostcllns (SI"I" fish. bony ganoid) holothurians 47.82.160 HomeosulITIIS [82 HyhollQliceras 127.128,129 HydrocrQspedota 115
hyd rozoans 32,82.84. 115 Hymenoptera (see wasps)
ferns
204 bony 165-73 bony ganoid 167- 71 eartilaginousganoid 167 lobe·finned 173 modern bony 171 ray-finned 165-71 shark-like cartilaginous 160-5 flies 152 foraminifera 32.36.42.43. 47.54.55.62.64.67.70. 73,74.82. 103 Francocaris
fungi
129
103
Ga1coidca 161 gastropods 47. 79. 82. 83. 84. 100. 120-1 Gum/ryillu 43 Gl!ocom(J 155.158 GI!OSIWruS 185 Ginkgo 1U7. 110
Limu/lls 79. SO. 138 Lioslrea 120 LililuSler 154, J57 Lililoblo(fo 144.145
lil:ards
86, 180-1. 187
Lobolt/olhyris
locusts
74.75,75.76
Lllmbricurill
Mocroplerygills 179, Magi/a 132,138
malaooslraeans 85,129-32
molluscs
55.81.82,119-29,
16' monerans
102
mysidaceans
R4,177-9.179 Il/oceTUmus 67.76. 120 insects 2.57. 73. 84. 86. 93. 96.100.141-52.204 invertebrates 112-60
Nl!ochl'loCl'ras Nepo 149
fridogorgmlia 117 ISc/I)'odus 165.168-9
Nodosaria
isopods
ISO
MorgirlUlillu 43 mayflies 142-3 .143 Mecochirus 58,79,85. I3J, 134. /J5 MesobeloslOmllm 146.148 Mesofimullls 58,78.79. SO. 138-40. 142. 203 Meso/all/ius 152 Millericrlfllls 153
'/!1yogrQmnla'
ichthyosaurs
119
146
nautiloids
115 129
84. 124--{J 127.129.132
Neu roptcrans (Set
laccwi ng~)
129 Odonata
jellyfish 2.59.84,89.90. 112-15
ophiuroids Oppeliu
Kalligrammo 149.150 Kaflimm/O/I 91. 182. 183
laccrtilians (see li7.ards) lacewings 149 I. IICllllostdfa
119
Lepidos,luria 180 LepidOleli 167. f68-9 LeplObmehiles 115 Leplofepirlrs B4. 90. 94_5. 171 Lihl'lf(lfi(ll/l 100. 144. 144 limpe lS (.1"1' 'I'mril(l') lil\1ulid~ S2. R9. %. 1117
(S€l"
dragonnies)
ISS. 158
OphiopsanlnlllS
82. 155
99
O rnithischia 185 Osteichthyes (see fish. 0011)') ostracods 46.47.73.74.112. 133.204 OSlrea 67. 76 oyslcrs (see a/~'o OSlrefllllH.I Lioslrell) 91 171.176
f'(U:hYlhrissops f'lIll1COCYfl/lri~
72. 110-11 ,
110-/1 I'"flll'())'c),lfiu m
pn lpigrmJcs 1,11 I'afr()\ f"h 1(,7
161, 162- J
Sys/emmic index
' 1'lJlel/o' 120 1"111.'//;"0 43 I>OIIIl~US 90 'phaeophytes' (jet algae. brown) l'h11smida (Set water skaters)
l'lwfidophoflls 171 l'h)'II01l1alllu 78. 103, 104 1'lIl11a 82. 120 1'lfhofl~lIo 44
planu 72.84,96, 103-1 1.204 non-vascular 103 vascular 103-11 plesiosaur.; 84.90_ 179-80 I'/esio/ewhis 121. 112 l'f~Ul'O$lJurU$ I'rohimon~uro
182.184 152
protists 46.64. 102-3 l'rolOh% lhur;a 160 I'r%spino;!; 161 l'se"daglJflid~s 126
I'$l'udorhina
161. 164 151. IJ2 ptcridop hytes 103-5 ptc ridosperms (Set seed ferns) l'l..,ocomo 90.153.156 1'lerWOClylus 14, 190.192 rtcrosaur,; 13.86.93. 187PUlldosirv:
90.204 1')'Clwphll.'bio
146. 147
(Jlliuqlle/OCIi/iIlO
43
Itadiolana 33, 34. 37, 46 r;Lllish 165 mys 82,84. 165 i'crtantians 13 1-2
rcrti1cs 11-13.14,37,56,57. 75.84.86.93.99. 173-90. 191.197,204
Squaloidca 161 sq uids 2.74,84 ,89,99,
Rhamphorhynchll$ 13. 188--9.190.190. 191 RlriZQSlOmites 114-15. J 14
starfish
rhynchocerhalians 86.9 1. ISO. 181. 182-4.204 rhynchoncllids 119 Rissoa 79.83.84. 121
12 1-3, l l2
82, 154
S/ttltosallrru 184 Sirphllnolilirioll 44 StemurllrrOIl 141
stomatopods 132 SlIbplmrilfi 98 Toromelliurll$
SaCCQComll
74.90. 153. 154,
155 Saurischia 185. 186 scallops (set £opecttn) Sci/ida
132.139
scyphozoans (St~ jellyfish) sea·cucumbers (u~ holothu rians) sea-lilies (see crinoidS) sea- urchi ns (Ste eehinoids) seed fern s n, 86. 106-7 seed·plants (Jet spcrmatophytes) selaehians (see sharks) Stpto/iplror;u 119 Suplllo 117 sha rks 82. 161,204 shnmps 79.83.90.99. \29--31 Solmrya 79,81.82,82.120 spcrm810phytes 103-11 Spllmodon 182.182 Splrenozamilts 107, /(]9 spiders 204 Spilrigera 120 ~po nges 26-34,37.57.19.
11 2
126.127,129,
130 tcle~ts
(see fish, modern bony) terebratulids 119 Telrugramnru 156.159 tonoises 204 TrachyttUlhis Tnmucfictyo"
122,123 112. 113
Trichoptera (st!eeaddis Ilies) turtles 84,173--7. In Urda 129 Urodts 170
vertebra tes
160-20 1
wasps 15 1 water scorpions 146-9 water skaters 144 wo rms 76,82,89 ' worms' I I 7 worms, an nelid 117 xiphosurans
78.80, 138--40
Zamites 107.108 Zeu8rhubdows 44
233
General index This mdex includes all SubjcC1solhcr than systematic namcs, which are covered In a separate indc~ Place namcs from individual ligures of the fossils are not mdexed. bUI references arc given to som~ oflhc figures in the first six chapt ers of the book where it is fel! they may be uscful (e.g. to gcncml
views of quarrics). Allmiihl. River
1.10,21.24.
31 ammonite rollmarks ammonite zones
68
(Tithonia n) 35 anoxicit)' (Stt lagoolllli waler, oxygen content of)
aptychi. ammonite 126. 129 aragomlc 49-54.100 Archtltoplfryx forgery
allegations 13 Archutopluyx spcdmens. comparison of 197 Baier. J. J . OryklOgfllphiQ
Norico...
10
bankkalk 28,37 Barthel. K . W. 65-7 Bear Gulch plattenkalk (USA) 205 bioslraljnomy marine 89-93 terrestrial 93-6 bioturbation 48 Bohemian Land Mass 57 Bohemian Massif 17. 25 Boreal Ocean 2.~ building material s (sn QUO tiles) 8 Buisonjl!. P. H . de 63 'calcispheres' 46 calcite 49-54.62,100 iron COntent of 62 magne siu m content of 51.
52-4 manganese content of 62 calcium carbonate che mist ry and mineralogy 49-55 carbon isotope studi es 54-5 Cerin plauenkalk 204 che rt layers 33.34.35
coccoid eyanobactcrial 46-7 concretions 99 coprolites 74-5.117.204 cough balls 75 CretaCCQusscdiments 19.
203 cyanobacteria l mats 64-5.68.73
fossils
oollections of 9-16 post-mortem features of 90. 179
trade in 9 Frischmann. Ludwig
13
58.
Daiting 37.96.111.135.185 Danube. Ri ve r 1.21.24.56 Darwin. Charles 11-12 death trails 58.79. 140.203 dendritic markings 39 diagenesis 42.49-55 of fossils 96-9 Doggcr (Stt Jurassic. Middle) Dol1nstein 24 dolomite 51
Germar. E. F. 10 grain si2:C distribution of flnll and faule 42-7 grai ns. studies of 41-8 gravestones 4 Grecn River plauenkalh (USA) 205 Gungolding 59.90.114.1.1 1 Haberle;n. Carl 11. 13 Habcrl ci n . Erns! 13 Hagen . A. 10
HQngrndr Krumme I.ugt canhquakes 37 Ebenwies 33 Eicllst;"itt 4. 14. 16. 2R. 35. 37.38-40.46.48. 58. 6 1. 63.67.68.70.74.79.90. 91. 92, 96. 114. 115. 12Q, 140.142.153.171. 184 facral pellets 46 faeces. fossil (sn coprohtes) mule 38-48.49.51-2.55.64. 67.68.70 flinO'; 38-48.49.51-2.55.64. 67.68. 70. 170 fossil prescrv3!ion -lU.59 ammonite siphllncles 63 by cyanobactcrial mm 65 hard part~ 100 holothun:U1Ih~lc1cs 16() pcde~tal preser'
"
st)ftpart \
lee Ages 24 IsotOpe slu(hes (Mt wulr, oxy~en and earl>on) Jllrn n1(\urU:IIIl~ (French) JuraSSIC
m.ld 1(K1.116
"
Haque! and Iijoula pJaucnkalks ( Lebanon) 205 1·ldlcr. Florian 14 Hemlebcn. C. 47-8 •.~2. 011 He rcynian orogeny 17 JlolO';mllden 179 HOfllSIl'i11 (Stt chert laye",1 Iiorstberg quarry .36 Hoyle. Fred 13 Huxley. T . H. 12 hypersalinity (sn logool1111 Wlllcr. 5.11i1l11y of)
IInmn
17 17
'III
General jndr:x
Early 17 L3Ic (su ulso Tithonian . Kimmeridgian and Oxfordian) 18.24-37. 56-7,7 1 Midd lc 17 Whilc 18 I..m.llfication 23 li.clhcim 2. 4.24.26,32.33, 58.96.11 1.112.119.120. 140. 155 , 171. 184 ,,"cupp, H 46---7,52, 62, 63. 60-70 li.lIllmcndgiall 57.203.204 ]J.1laeogeography 26-34 "rm",nf' I..llg~ beds 37 13. 34.57.59,202, 203 life in 73-9 I.II:oonal water 59-70 \I~yge n co ntent of 34. 37. 55.60-3. 90 '"-llillityof 34.55.59-60. 64,73,74, n.90, 115 'Iasnation of 58-9,64.73 upwelling of 63-4 I .'lIdshuI 18 1.lIlgenaltheim 2.14,58.74,
I;'g''''ll
'il
1.11,,1<.:.
76 Jurassic. Earl y)
pl~nktonie
I,."
(s~..
limo;
4
limo.:,lone .lIglliaecous 25.28.37.202 hlhugr;lphie 2 Imcntic (su Hinz) 1,l"ty 2 I'li re 26.35. 202 hlhtlgmphy 2.4-6.8.38. 41 III.KWf.. ~sib.
of
o(:curre nce
4U I
Juras:.ic, I..;u.·) quarry 16,40.41. n, 4M, 55
".llm
(.Ir..
't.l~hc r):
It1l'IIHl I'IOlII)III\IIIC ~
.\
Mncr, Ikrnllilln \\." 10 "' .. r \lljl~\d\, ,,,:cllrrenn' of II M
Middle Agcs. usc or plattenkalk in 4 Miocene 22.23 Mlileld..lIlsch .. Scilwell.. 19. 25.57.86 Monheim 37 Monlseeh plallenkalk 203 Momsheim beds 27.35-7. 61. 63. 68, 126, 127 MOller.llerr 14 Munich I . 16 Munster, Graf Georg du 10 museums II. 13. IS. 16 Neuburg 21.. 37. 103. 115 Neumayer quarry 39 Nusplingen plallenkalk 203 Oppel. Albert 10 Orca basin. Gulf or Mexico 60 Ostrom. John 14 Owen. Rieh;lrd 12.13 Oxfordi~n
palaeogeography 25-6 oxygen conl ent of water (su wul..r lagoonal water) oxygen isotope studies 53-4. 55.71
pI;l11en kalk basins 3.4, 26-37 wate r depth in 57-8 plallcn kalk cxploitation . his tory of 4-8 platten kalks, OIher 67-8. 203-5 )lres~urc solution 51 pyrite 35,62 4uarrics 2. 4. 16.38 quarry ing methods 8 Qualernary weathering
Reden bacher. Dr 13 reefal communilies 79-84 reefal d ebris 47,54.65 reefs 3, 14. 19.32-4.36. Sf>-B. 71. 89. 203 Regen sbu rg 19 Regell sbu rg embaymen t 18 Ren aissance. usc of plattcnkalk in 4 reptili a n skull openings 173. 177 Rles 19 Ries metcorile eraler 22. 25 ROgli("1g Beds 27.35 Romans. usc of plattenkalk by
Painten 4.33.58.61.68.79. 96 palaeoclimate 71 palaeocurrent Indicators 91-3 palaeoenviroll("1en I rcstricled basin model S<>-8 subaerial expostlrC hypothesis 56 palaeogeography 24-37 palaeotemperature calculati ons 71 PalaeOZOIc rocks 17. 23 l'UIJil"rsdur!er ('paper shale ') 37 1';Ippen hCl m 13 I'CI'Illian \Cdl!l1 C1l1~ 17 l'ful lP3tnl 59.79 .90.1 14. I :!I 1'11I/lI"'rl",,~
,
ROle "'1ers ..1 Lag .. (red marl byer) 34 sahnity of water (su IInder lagoonal water) Schernfeld 38. 43 .48 Schlo.heim. Baron Friedrich von 10 scul ptures 4 sediment deposit ion ll1eorics 65-70 scdi ment transport by ~at et 72 by ..... ind 72 sedi ments allochthonous 67-8 aut ochthonous 67-8 Scilacher. A. 67-8 ScncEelder, Alois 4-6 SIf,fr o-Erlwlllllrg
2
24
Soht r l ;tke. SIn;1!
37
55
General index
Solnhofcn 2-4,14, 16,20, 21,31 ,33,35,37,38-40, 46,48, 6 1,63,67,68, 70,74,79,91, 140, 142 Solnhofcn Plancnkalk 2,4, 19,27,33,38,49,55,67 and many instanccs in Chaptcr7 characteristics of 202-3 day chemistry of Lower 35,61 Upper 35-7,61, 127 Southern Franconian Alb 1,
sa,
n
2,4
geological hiSlOry of 17-24 palaeoclimate of 71-3 palaeoecology of 71-88 palaeoenvironment of 56 palaeogeography of 24--37 sponge-algal mounds 3, 26-32, 58, 67, 73, 79, 112,
202,203, 204 Spurmschie[er 35 Stone Age, use of plattenkalk in 4,9
strontium in c3rbonat es and pore water 52-4 styloli tes 52 Swabian Alb 203 terrestrial ecosyslems 84-8 Tertiary deposils 17 Tertiary uplift 23 Tethys Ocean 18- 19,25,33, 37.57.61 tiles floor and wall 4 roof 4.7-8 Tithonian 2 palaeogcography 34--7 Toulouse-Lalltrec lithographs 6 trace fossils 35,56.74--5. 202,204 Trenllfmde Kmmme Luge 35,
36 Treuchtlingcn marble 27,28. 124 Triassic sediments 17, 23
turbidites
34,67-8, 203
uses of plancnkalk 4-8 Veiler, J , 62 vencbrate evolution 173 Vinddieisch Land 17.18-19, 25
Viohl. Gun te r
14,63
Wagner. Andreas 10 Walther, Johannes Die Fall/In dt'r Solnhofem!r I'IOlltmkulke 13 WcJlnhofcr. Peter 14 Wchcnburg ]S5 Wickramasinghe. Cha nd ra 13 Winte rshof 23, 49 bndt 153. ]S5, 171 zone fossils 127 Z ...OI/-Aposte/-Ftlstn 3 1
The celebrated Solnhofen Limestone is among the most important foss il deposits because of its astonishing diversity of organisms , many exquisitely preserved. Marine and terrestrial creatures and plants, buried 150 million years ago in soft lagoonal muds, provide a unique glimpse into the true diversity of Jurassic life. Articulated skeletons are preserved, as well as some soft-bodied animals that otherwise would be too delicate to survive fossilisation. Among the highlights are superbly preserved jellyfish , crustaceans, sq uid , fish and flyi ng reptiles. Perhaps most important of all is Archaeopteryx - the celebrated ' missing li nk' which has the skeleton of a dinosaur but is covered in feathers , revealing a crucial evolutionary transition between the reptiles and birds. Solnhofen opens a window into a vanished world , and reveals the unexpected richness of a land and sea teeming with life. This book is a revised and updated translation of Werner Barthel's classic work Solnhofen: Ein Blick in die Erdgeschich/e. In revising the text , Nicola Swinburne and Simon Conway Morris have added a considerable amount of new material whilst preserving the spirit of tbe original book. This is an authoritative account of the geological history , palaeoecology , palaeoenvironment and fossil taxonomy of th is classic location. Not only will it be of great interest to palaeontologists and evolutionary biologists, but it will also be of value to amateur collectors , natural historians and also those with an interest in the history of life. 'This book is an excellent testament to one of the most fa mous limestones in the geologic record. ' American Scientist 'Geologists are now indebted to Nicola Swi nburne and Simon Conway Morris for an excellent general survey .. . of the considerable body of research by German sedimentologists and taphonomists during the last 25 years'. Nature
Cover design by Marcus Askwirh
IS BN 0-521-45830- 7
CAMBRIDGE UNIVERSITY PRESS 9
![Solnhofen ; a study in Mesozoic palaeontology - K.W. Barthel ; [translated and revised by] N.H.M. Swinburne ; [edited by] S. Conway Morris Cambridge ; New York : Cambridge University Press, - ISBN 0-521-45830-7](https://epdf.mx/img/300x300/solnhofen-a-study-in-mesozoic-palaeontology-kw-bar_5a49e435b7d7bc850ca59cb8.jpg)
