Primeros restos cefálicos de Steneosaurus (Crocodylomorpha: Teleosauridae) del Jurásico Superior de Oker (Baja Sajonia, Alemania

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Colecciones : Studia Geologica. Salmanticensia, 2008, Vol. 44 n. 2
Fecha de publicación : 22-sep-2009
[EN] Two remains of the head region of the Late Jurassic marine crocodile Steneosaurus brevirostris Owen, 1842 are described from the Kimmeridgian of the Langenberg near Oker, Lower Saxony, Germany. They consist of fragments of a rostrum and a lower jaw (mandible) and represent the first record of parts of the head from this locality. A comparison with similar materials of the nearly contemporary Steneosaurus jugleri (V. Meyer, 1845) and St. picteti (De Tribolet, 1873) suggest that the latter two species are synonymous with St. brevirostris.[ES] Se describen dos restos cefálicos del cocodrilo marino Steneosaurus brevirostris Owen, 1842, del Jurásico Superior, provenientes del Kimmeridgiense del monte Langenberg cerca de la comunidad de Oker, Baja Sajonia, Alemania. Se trata de fragmentos de un rostrum y una mandíbula inferior y representan el primer hallazgo de partes de la cabeza en esta localidad. La comparación con materiales parecidos de Steneosaurus jugleri (V. Meyer, 1845) y St. picteti (De Tribolet, 1873), casi contemporáneos, hace suponer que las últimas dos especies son sinónimas con St. brevirostris.
Publicado el : martes, 22 de septiembre de 2009
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Fuente : Gredos de la universidad de salamenca
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ISSN:0211-8327
StudiaGeologicaSalmanticensia,44(2):pp.187-201
FIRSTREMAINSOFTHEHEADOF S T T E E LE N O E S O A S U A R U I R D U A S E)(CFRROOCMOTDHYELLOAMTOERJPUHRAA:SSIC OFOKER(LOWERSAXONY,GERMANY)
[Primerosrestoscefálicosde Steneosaurus (Crocodylomorpha:Teleosauridae)del JurásicoSuperiordeOker(BajaSajonia,Alemania)]
Hans-VolkerK ARL (*) ElkeG RÖNING (**) CarstenB RAUCKMANN (**) NilsK NÖTSCHKE (***)
(*):GeocenteroftheUniversityGöttingen.Dpt.Geobiology.Goldschmidtstrasse,3. D-37077Göttingen.Correo-e:hkarl@uni-goettingen.deorhvkarl@web.de (**):InstituteofGeologyandPalaeontology.ClausthalUniversityofTechnology. Leibnizstrasse,10.D-38678Clausthal-Zellerfeld.Correo-e:Elke.Groening@tu- clausthal.de,Carsten.Brauckmann@tu-clausthal.de (***):DinosaurParkMünchehagen.AlteZollstrasse,5.D-31547Rehburg-Loccum. Correo-e:palaeo_nils@hotmail.com
(F ECHADERECEPCIÓN :2008-07-25)(F ECHADEADMISIÓN :2008-09-02) BIBLID[0211-8327(2008)44(2);187-201]
RESUMEN :Sedescribendosrestoscefálicosdelcocodrilomarino Steneosaurus brevirostris Owen,1842,delJurásicoSuperior,provenientesdelKimmeridgiense delmonteLangenbergcercadelacomunidaddeOker,BajaSajonia,Alemania. Setratadefragmentosdeunrostrumyunamandíbulainferioryrepresentanel primerhallazgodepartesdelacabezaenestalocalidad.Lacomparacióncon materialesparecidosde Steneosaurusjugleri (V.Meyer,1845)y St.picteti (De Tribolet,1873),casicontemporáneos,hacesuponerquelasúltimasdosespecies sonsinónimascon St.brevirostris . Palabrasclave:Crocodylomorpha,Neosuchia, Steneosaurusbrevirostris ,Jurásico Superior,Kimmeridgiense,Oker,Alemanianoroccidental.
©EdicionesUniversidaddeSalamancaStud.Geol.Salmant.,44(2),2008:pp.187-201
H.-V.K ARL ,E.G RÖNING ,C.B RAUCKMANN &N.K NÖTSCHKE 881 Firstremainsoftheheadof Steneosaurus (Crocodylomorpha:Teleosauridae)fromthe LateJurassicofOker(LowerSaxony,Germany)
ABSTRACT :TworemainsoftheheadregionoftheLateJurassicmarinecrocodile Steneosaurusbrevirostris Owen,1842aredescribedfromtheKimmeridgianof theLangenbergnearOker,LowerSaxony,Germany.Theyconsistoffragments ofarostrumandalowerjaw(mandible)andrepresentthefirstrecordofpartsof theheadfromthislocality.Acomparisonwithsimilarmaterialsofthenearly contemporary Steneosaurusjugleri (V.Meyer,1845)and St.picteti (DeTribolet, 1873)suggestthatthelattertwospeciesaresynonymouswith St.brevirostris . Keywords:Crocodylomorpha,Neosuchia, Steneosaurusbrevirostris ,LateJurassic, Kimmeridgian,Oker,LowerSaxony,northwesternGermany.
INTRODUCTION AsalreadydocumentedbyK ARL etal. (2006)intheircompilationonLate JurassicandEarlyCretaceouscrocodilesfromnorthwesternGermany, Steneosaurus remainsfromthe“Kimmeridge”ofOker(closetothenorthern slopeoftheHarzMountainsinLowerSaxony/Germany)werepreviously restrictedtoisolatedteethandvertebrae.Inthemeantimetheprospecting teamofthe“DinosaurParkMünchehagen”discoveredandpreparedthefirst fragmentaryrostrumandapartofthelowerjaw(mandible)whichcanbe assignedtothespecies Steneosaurusbrevirostris Owen,1842.
GEOLOGICALANDSTRATIGRAPHICALSETTING Thegeologyandbiostratigraphyaswellasthehistoryofquarryinginthe LangenbergsectionhavealreadybeenpublishedindetailbyK ARL etal. (2006).Therefore,hereweonlyneedtorepeatthemostimportantdata: Thelargequarryofthe“RohstoffbetriebeOkerGmbH&Co”issituated atthewesternslopeoftheLangenberg,betweenOkerandSchlewecke. AccordingtoF ISCHER (1991),itexposesanearly200mthickandlargely calcareoustomarlyLateJurassicsequencewhichreachesfromthe“Lower CoralOolite”(“UntererKorallen-Oolith”;higherOxfordian;approximately Perisphinctespumilis Zone)uptothe“UpperKimmeridge”(astraditionally usedinLowerSaxony;=LowerKimmeridgianoftheBritishstratigraphy; approximately Aulacostephanusautissiodorus Zone).Theexactcorrelation withthesubborealstandardzonationbasedonammonoids(G RAMANN etal. , 1997)isfarfromclearbecauseammonoidsareextremelyrarein theLangenbergquarry.AccordingtoL OOK (1985:393),thesedimentsofthe LowerandMiddleCoralOolitearemarine;upsection,startingwith theUpperCoralOolite,environmentsbecamemoreandmorebrackish(see figure1).Duringthe“Kimmeridge”theLangenbergareawaspartofa shallow-waterbasin;thedepositionalenvironmentinthistime-spanis interpretedasalagoonorbay.Thedetailedstratigraphyisbasedon microfossils(P APE ,1970;Z IHRUL ,1990).
©EdicionesUniversidaddeSalamancaStud.Geol.Salmant.,44(2),2008:pp.187-201
H.-V.K ARL ,E.G RÖNING ,C.B RAUCKMANN &N.K NÖTSCHKE Firstremainsoftheheadof Steneosaurus (Crocodylomorpha:Teleosauridae)fromthe LateJurassicofOker(LowerSaxony,Germany)
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Figure1.TheKimmeridgianpartoftheLangenbergsectionofOker , LowerSaxony , northwesternGermany , preparedbyMudroch&Knötschke , usingbasicdatapublishedby F ISCHER (1991).
©EdicionesUniversidaddeSalamancaStud.Geol.Salmant.,44(2),2008:pp.187-201
H.-V.K ARL ,E.G RÖNING ,C.B RAUCKMANN &N.K NÖTSCHKE 091 Firstremainsoftheheadof Steneosaurus (Crocodylomorpha:Teleosauridae)fromthe LateJurassicofOker(LowerSaxony,Germany)
ThesectionispartofthesouthernflankoftheSubhercynianSyncline. DuetothestrongupliftoftheHarzMountainsinpost-Santoniantimes,the sequenceisoverturnedanddipstothesouthwithanangleofabout70°. Thereforetheimpressiveandlargebeddingplaneswhicharewidelyvisible fromthesoutharebottomplanesofthestrata.Thehardcomponentsofthe sequenceareresistanttoerosionandformanarrowandbarelywooded ridgeparalleltothemainfaultofthenorthernslopeoftheHarzMountains (“Harz-Nordrand-Störung”,“NorthernBorderFaultoftheHarzMountains”). ThewholeLangenbergareaanditssurroundingsareamajorpartofthe “GeologicalGermanSquareMile”andinternationallywell-knownforthe strongandwellexposedtectonicsincludingremarkablestratigraphicgaps anddiscordancesinalotofoutcrops. ThecompletesequencehasbeendescribedindetailbyP APE (1970),Z IHRUL (1990)andF ISCHER (1991);compilationsinalargerregionalandstratigraphic frameareincludedinL OOK (1985:388-393)andG RAMANN etal. (1997). Commonfossilsofthe“Kimmeridge”attheLangenbergarebivalves, gastropods,brachiopodsandichnofossils;inhigherpartsofthesection,even nautiloidsoccur.AspointedoutbyS TURM &B RAUCKMANN (1999:53),remains ofthecolouringarenotrareincertainbivalvesandgastropods.Somelayers, inparticularintheso-called“SecondQuarry”attheeasternslopeofthe Langenberg(wherethesamesequenceisexposed),yieldverysmall fragmentsofanamber-likeresin. TheLangenbergquarrybecamestillmorefamousafterthediscoveryof dinosaurskullsandotherremainsin1998(S ANDER etal. ,2006).Other vertebratefossils(mainlyfishes,butalsocrocodiles,turtles,etc.)arepresent; morerecently,F ASTNACHT (2005)presentedadetaileddescriptionofa dsungaripteridpterosaurandK ARL etal. (2007)fortheplesiochelidand hylaeochelidturtles. Inthemeantimeateamofpalaeontologistsjointlywiththe“Dinosaur ParkMuenchehagen”(“Dinosaurier-FreilichtmuseumMünchehagen”) carefullysecures,collectsandpreparesthenowlargematerialsofthe “DinosaurCemetry”oftheLangenberg.Forthefuture,aspecial“Jurassic Museum”intheLangenbergisplannedincooperationwiththe“Dinosaur ParkMuenchehagen”.
MATERIALS Thespecimensdescribedinthepresentcontributionaredepositedinthe collectionsofthe“DinosaurParkMuenchehagen”(“Dinosaurier-Freilichtmuseum Münchehagen”),numbersDFMMhFV870andDFMMhFV878.
SYSTEMATICPALEONTOLOGY LegionArchosauromorphavonHuene,1946
©EdicionesUniversidaddeSalamancaStud.Geol.Salmant.,44(2),2008:pp.187-201
H.-V.K ARL ,E.G RÖNING ,C.B RAUCKMANN &N.K NÖTSCHKE Firstremainsoftheheadof Steneosaurus (Crocodylomorpha:Teleosauridae)fromthe LateJurassicofOker(LowerSaxony,Germany)
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Stud.Geol.Salmant.,44(2),2008:pp.187-201
H.-V.K ARL ,E.G RÖNING ,C.B RAUCKMANN &N.K NÖTSCHKE 291 Firstremainsoftheheadof Steneosaurus (Crocodylomorpha:Teleosauridae)fromthe LateJurassicofOker(LowerSaxony,Germany)
SuperorderCrocodylomorphaWalker,1968 OrderNeosuchiaBenton&Clark,1988 SuborderThalattosuchiaemend.Fraas,1901 FamilyTeleosauridaeGeoffroySaint-Hilaire,1831 SubfamilyTeleosaurinaeGeoffroySaint-Hilaire,1831(sensuLydekker,1887) GenusSteneosaurusGeoffroySaint-Hilaire,1825
TYPESPECIES:“CrocodiledeQuilly”Cuvier,1824= Steneosaurus megistorhynchus (Deslongchamps,1866)(fideD ESLONGCHAMPS ,1866; L YDEKKER ,1888;K UHN ,1936). NOMENCLATURALREMARKS(basedmainlyonS TEEL ,1973):When establishing Steneosaurus “pourlesreptilesfossilsconnusjusqu’àcejour souslenomdeGavialsd’Honfleur”,G EOFFROY S AINT -H ILAIRE (1825)proposed twospecies, Steneosaurusrostro-major [correctspellingaccordingtoICZN, article32.5.2.3.: St.rostromajor ]and Steneosaurusrostro-minor [correct spelling: St.rostrominor ],theformerbeingC UVIER ’s“gavialàmuseauplus allongé”andthelatterhis“gavialàmuseaupluscourt”.Howevernoneof thesetwospeciesisappropriatelydefined.Infact, St.rostrominor belongsto Metriorhynchusgeoffroy V.Meyer,1832,andthustothetypespeciesofa differentgenus.Furthermore,C UVIER ’s“gavialàmuseauplusallongé”(and thus Steneosaurusrostromajor )isunfortunatelybaseduponacombinationof twospecies: Steneosaurusedwardsi (Deslongchamps,1866)[snout;Early Oxfordian]and Metriorhynchussuperciliosus (Deslongchamps,1866)[skull; Oxfordian].Thespeciesname Steneosaurusmegistorhynchus wasattributed toG EOFFROY S AINT -H ILAIRE byD ESLONGCHAMPS (1866)whosubsequently(1869) reiteratedhisopinionthat Steneosaurusmegistorhynchus shouldreplacethe doubtful St.rostromajor ,andbothL YDEKKER (1888)andK UHN (1936)accepted St.megistorhynchus . Butthisdiscussiondoesnotreallydissolvethenomenclaturalproblem becauseitneglectsthatonlyafteradefiniteselectionofatypespecimen (snoutorskull)of St.rostromajor itcouldbedecidedwhetheritis appropriateforacleardefinitionofthisspecies.Ifthelatterappearstobe true, St.rostromajor couldbecomeeithertheoldersynonymof Steneosaurus edwardsi or Metriorhynchussuperciliosus .Intheformercase St. megistorhynchus ,inthelattercase Metriorhynchussuperciliosus willbea youngersynonymof St.rostromajor .Toourpresentknowledgewecannot decidewhetheratypespecimenof St.rostromajor hasalreadybeenselected ornot.Ifnot,thisprocedurewouldbeafirststepinarevisionoftheoriginal materialsofthespeciesnamesdiscussed. CHARACTERS(fromS TEEL ,1973:26-28): Steneosaurus ischaracterizedbya snoutvaryinginrelativelengthandofmoreorlessroundedcross-section anteriorly,becomingflattenedintheposteriorpart.Theobliquelytruncated
©EdicionesUniversidaddeSalamancaStud.Geol.Salmant.,44(2),2008:pp.187-201
H.-V.K ARL ,E.G RÖNING ,C.B RAUCKMANN &N.K NÖTSCHKE 391 Firstremainsoftheheadof Steneosaurus (Crocodylomorpha:Teleosauridae)fromthe LateJurassicofOker(LowerSaxony,Germany)
premaxillaearemarkedlydeflectedattheirexpandedextremityandeach contains4or5teeth.Orbitofregularshapeandupwardlydirected,but frequentlymorelaterallyplacedthanin Teleosaurus .Asmallantorbitalfenestra ispresentandthepostorbitalbarisapproximatelyatrightanglestothelong axisoftheskullsothattheposteriorborderoftheorbitissituatedwellin advanceofthesupratemporalopening.Infraorbitalbardeepandupper temporalarcadelackingsculpture.Frontalbonesmallandskulltablegreatly flattenedandisodiametricwiththelengthacceedingthebreadth.The supratemporalfenestraeareverylarge,elongateandoftrapezoidshapewith roundedangles.Incomparisonwiththeorbitstheyareofgreatersizethanin Teleosaurus .Alveolarborderwithoutundulationsandthepalatalvacuitiesare largeandthepterygoidsbearprominentlateralprocesses.Internalnares roundedandsituatedinadvanceofthetemporalfenestrae,theyarerather smallerthanin Teleosaurus .Teethslantingoutwardsatanangleanddisplaying twolongitudinalcarinae.Numberofcaudalvertebrae:approximately40. KNOWNDISTRIBUTION:EarlytoLateJurassicofEurope,EarlyJurassic ofSouthAmerica,MiddleJurassicofMadagascar,andJurassicofMorocco (S TEEL ,1973). PALAEOECOLOGICALREMARKS:AccordingtoB ILLON -B RUYAT etal. (2005) Steneosaurus showsnearlythesamerangeof d 18 Ovalues(19,9‰to 21,9‰)asthe“fish” Lepidotes andotherPycnodontiformesfromfive collectingsitesinlithographiclimestoneinwesternEurope.Thisfact suggeststhatatleasttheseOsteichthyeswereembeddedinsedimentsclose totheshore,butoriginallylivedoffshoreindeeperandcoolerwater. Steneosaurus wastheirpossiblepredator.
Steneosaurusbrevirostris Owen,1842 SYNONYM: Steneosaurus aff. brevirostris Owen,1842,K ARL ,G RÖNING , B RAUCKMANN ,S CHWARZ &K NÖTSCHKE ,2006:69,fig.12A. LOCALITYANDHORIZON:Forgeneraldataseechapter“Geologicaland stratigraphicalsetting”.Theblockswhichyieldedthespecimensdescribedin thepresentarticlewerealreadybrokenoff;thustheexactpositionwithinthe sequenceisnotclearlyknown.Duetotheirthicknessandlithologythey couldhavehadtheiroriginperhapsinbed53(seefigure1). PREVIOUSMATERIALSFROMOKER:K ARL etal. (2006)listed fragmentarymaterialsrelatedtothattaxonin“opennomenclature”under Steneosaurus aff. brevirostris ,asforexampleDFMMhFV510:neuralarchof caudalvertebra;DFMMhFV353neuralarch(?);DFMMhFV330,DFMMhFV 281,DFMMhFV474,DFMMhFV334,DFMMhFV335,DFMMhFV609, DFMMhFV327(9.3.2001),DFMMhFV611,DFMMhFV615(1999),DFMMh FV616,DFMMhFV618,DFMMhFV619,DFMMhFV621,DFMMhFV622, DFMMhFV272-275,DFMMhFV392:teeth(completeandfragmentary);MG 865trunkvertebra(MuseumGoslar).
©EdicionesUniversidaddeSalamancaStud.Geol.Salmant.,44(2),2008:pp.187-201
H.-V.K ARL ,E.G RÖNING ,C.B RAUCKMANN &N.K NÖTSCHKE 491 Firstremainsoftheheadof Steneosaurus (Crocodylomorpha:Teleosauridae)fromthe LateJurassicofOker(LowerSaxony,Germany)
MAINCHARACTERS(basedontheteeth):Teethverylong,caniniform, withoutlateralcrests,butwithsomelateralstriae.
MORPHOLOGYOFTHENEWSPECIMENS
(1)Fragmentoftherostrum:dfmmhfv870 Measurements(inmm):Preservedlength=73;preservedwidth=16. Widthofexternalnasalopening=8.Lengthofteeth-bearingsections:left row=71;rightrow=61. Preservation:Fragmentofrostrumthreedimensionallypreserved.Several transversalfractures:Rostrumthereforedorsallywithslightconcavevaulting. Posteriorpartbrokenoff.Anteriorpartfractured,onlyleftsideofpremaxilla largelypresent. Dentition:Notasingletoothcompletelypreserved,4teethoftheright rostralsidebrokenoffwithintheiralveoles.Leftrow:3alveoleswithinthe premaxilla,9alveoleswithinthemaxilla.Rightrow:1alveole,flankedby2 fragmentaryreplacementaryteethattheposteriorendofthepremaxilla;8 alveoleswithinthemaxilla.
Fragmentofthelowerjaw:dfmmhfv878 Measurements(inmm):Preservedlength=184.Lengthofpreserved mandibularsymphysis=51.Lengthofcompletepreservedpostsymphysal rightbranchofmandible=130.Lengthofintramandibularwindow:47. Lengthofpreserveddental=83.Lengthofsurangular=117.Lengthof angular=109.Heightofrightposteriorbranchofmandibleattheposterior endofintramandibularwindow=16.Lengthofteeth-bearingsections:left row=66;rightrow=60. Preservation:Excellentlythreedimensionalpreservation.Onlyfew fractures.Atleasttheanteriortwothirdsofmandibularsymphysisbrokenoff. Rightposteriorbranchofmandiblecomplete,leftposteriorbranchonly preservedbytheanteriorthird. Anglebetweenthetwopostsymphysalbranchesofthemandible=50º. Dentition:Leftrow:12alveoles,2.,4.,6.,7.,8.,10.and12.alveole(seen fromtheanteriorpart)withteeth(7.,8.and10.toothcompletelypreserved). Rightrow:11alveoles,(fromanterior)1.,2.,4.,6.and8.alveolewithteeth (1.toothcompletelypreservedandwithalengthof3,8mmthelargestone).
CHARACTERANALYSIS (1)Snoutshort[0]orsnoutlong[1];
©EdicionesUniversidaddeSalamancaStud.Geol.Salmant.,44(2),2008:pp.187-201
H.-V.K ARL ,E.G RÖNING ,C.B RAUCKMANN &N.K NÖTSCHKE 195 FirstremainsoftheLhateeadJuorafs S s t i e c n o e f os O a k u e r r us (L(oCwroecroSdayxloonmyo,rGpehra:maTnelye)osauridae)fromthe (2)Snoutanteriorlyflattened[0]ormoreorlessroundedincrosssection[1]; (3)Teethslender,withsharplypointedcrowns[0]orbluntwith roundedcrowns[1]; (4)Mandibularsymphysisshorterthan50%oflengthofjaw[0]orof samelengthormorethan50%[1]; (5)Naresofpremaxillarsdirectinganteriorly[0]ordorsally[1].
DATAMATRIX Steneosaurusleedsi 10110, Steneosaurusdurobrivensis 01000, Steneosaurus brevirostris 00010, Steneosaurusjugleri 00010,Langenberg00010.
OUTFILEBYDOLMOVE(JosephF ELSENSTEIN ) (Langenberg,( Steneosaurusjugleri ,( Steneosaurusbrevirostris ,( Steneosaurus durobrivensis , Steneosaurusleedsi ))));
OUTFILEBYPARS(JosephF ELSENSTEIN ) Discretecharacterparsimonyalgorithm,version3.6a3,shows1commontree: (Langenberg:0.00, Steneosaurusjugleri :0.00, Steneosaurusbrevirostris :0.00, Steneosaurusdurobrivensis :2.00, Steneosaurusleedsi :2.00);
TREEBYTREEVIEW(RodericPage)
DISCUSSION
Langenberg
Steneosaurusjugleri
Steneosaurusbrevirostris
Steneosaurusdurobrivensis
Steneosaurusleedsi
nA
©EdicionesUniversidaddeSalamancaStud.Geol.Salmant.,44(2),2008:pp.187-201
H.-V.K ARL ,E.G RÖNING ,C.B RAUCKMANN &N.K NÖTSCHKE 691 Firstremainsoftheheadof Steneosaurus (Crocodylomorpha:Teleosauridae)fromthe LateJurassicofOker(LowerSaxony,Germany)
extensivelistof Steneosaurus specieswasprovidedbyK REBS (1962).Similar andcloselyrelatedspecieshavebeendocumentedfromseveralJurassic sectionsinGermanyandSwitzerland. AcomparisonofallthepreviouslydistinguishedJurassicspeciesof Steneosaurus suggeststhatthetotalnumberseemstobetoolarge.Most ofthemhavebeenbaseduponincomparablefragmentarymaterials.Therefore wedonotwonderthatthenumberhasbeenstronglyreducedafterrevisions bymodernmethods.Forexample,W ESTPHAL (1961,1962)minimizedthe numberofLateLiassiccrocodilesfromGermanyandGreatBritaintoonlyfive speciesinthreegenera: Pelagosaurustypus , Platysuchusmultiscrobiculatus , Steneosaurusbollensis , Steneosaurusbrevior and Steneosaurusgracilirostris . W INCIERZ (1967)recorded Steneosaurus aff. bollensis fromtheLateLiassicof HondelagenearBrunswickintheSubhercynianBasin. A DAMS -T RESMAN (1987)analyzedtheMiddleJurassic(Callovian) Teleosauridae Steneosaurus and Mycterosuchus ofCentralEnglandbyusing 12cranialmeasurementsand8quotientsandcouldrestrictthenumberto twoclearlydistinctspecies: Steneosaurusleedsi Andrews,1909and St. durobrivensis Andrews,1909. Thefirstspeciesischaracterizedby:Elongated,slenderrostrum; preorbitallength72%ormoreoftotallengthofskull.Considerablevariation indegreeofseparationofnasalsandpremaxillae;thisdistanceaccountsfor 45-62%oflengthofrostrum.Teethslender,withsharplypointedcrowns, fortyormoreineachmaxilla.Mandibularsymphysisc.58%oflengthofjaw. Thesecondspeciesdiffersby:Shortrostrum;preorbitallengthc.60%or lessoftotallengthofskull.Nasalsandpremaxillaeseparatedby36-56%of totallengthofrostrum.Teethblunt,roundedattips;crownsbecome increasinglybluntassizeofskullincreases;twenty-eigthtothirtyteethin eachmaxilla;mandibularsymphysisc.40%oflengthofjaw. Moreinterestingforcomparisonwiththepresentmaterialsof St. brevirostris arethefollowingnearlycontemporaneousLateJurassicEuropean species[inbrackets:thematerialonwhichthespeciesarebased]: 1. Steneosaurusblumenbachi Deslongchamps,1868[upperjawsegment]; 2. Steneosaurusbouchardi Sauvage,1872[incompleteskull,lowerjaw, vertebrae,dermalplates,teeth]; 3. Steneosaurusjugleri (V.Meyer,1845)[teeth,vertebrae]; 4. Steneosaurusmegarhinus (Hulke,1871)[slenderrostrum]; 5. Steneosaurusmorinicus Sauvage,1872[lowerjawfragment,2 vertebrae]; 6. Steneosauruspicteti deTribolet,1873[vertebrae,ribs,dermalplates,teeth]; 7. Steneosaurusrecurvirostris Lennier,1889[maxillaryportionofupper jaw,imperfectlowerjaw].
©EdicionesUniversidaddeSalamancaStud.Geol.Salmant.,44(2),2008:pp.187-201
H.-V.K ARL ,E.G RÖNING ,C.B RAUCKMANN &N.K NÖTSCHKE Firstremainsoftheheadof Steneosaurus (Crocodylomorpha:Teleosauridae)fromthe LateJurassicofOker(LowerSaxony,Germany)
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Plate1. Steneosaurusbrevirostris Owen , 1842 , FV870 , fragmentoftherostrum. 1=palatinalview , 2=lateralviewofrightside , 3=dorsalview , 4=lateralviewofleftside; scalebar3cm.
©EdicionesUniversidaddeSalamancaStud.Geol.Salmant.,44(2),2008:pp.187-201
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