A limulid trackway from the Late Jurassic (Tithonian) Lagerstätte of Canjuers (Var, France)

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The first record of an invertebrate trackway from the lithographic limestones of the Canjuers Lagerstätte is described here. The preserved part of the trackway is approximately 39 cm long and 17 cm wide; it consists of two successive sets of imprints

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  C.R.Palevol12(2013)181–189 ContentslistsavailableatSciVerseScienceDirect Comptes   Rendus   Palevol www.sciencedirect.com General   palaeontology,   systematics   and   evolution   (Palaeoichnology) A   limulid   trackway   from   the   Late    Jurassic   (Tithonian)Lagerstätte   of    Canjuers   (Var,   France) UnepistedelimulidédansleLagerstätteduJurassiquesupérieur (Tithonien)deCanjuers(Var,France) Claire   Peyre   de   Fabrègues   ,   Ronan   Allain ∗ MuséumNationald’HistoireNaturelle,DépartementHistoiredelaTerre,CentredeRecherchessurlaPaléobiodiversitéetlesPaléoenvironnements(CR2P),UMR7207(CNRS/UPMC),CP38,57,rueCuvier,75231Pariscedex05,France a   r   t   i   c   l   e   i   n   f   o  Articlehistory: Received16October2012Acceptedafterrevision13May   2013Availableonline9July2013PresentedbyPhilippeTaquet Keywords: CanjuersFranceTrackwayImprints JurassicTithonianLimulid Kouphichniumlithographicum a   b   s   t   r   a   c   t The   first   record   of    an   invertebrate   trackway   from   the   lithographic   limestones   of    the   Can- juersLagerstätte   isdescribed   here.   The   preserved   part   of    the   trackway   isapproximately39   cm   long   and17cmwide;   it   consists   of    two   successive   sets   of    imprints   and   the   beginningof    athird   one.   Two   kinds   of    imprints   have   been   recorded:   the   first   one,   well-preserved,   istetradactyland   the   second   one   is   straight,   narrow   and   in   setsof    two   or   three   imprints.The   tracks   described   inthis   paper   are   similar   to   the   type   specimen   of    the   ichnogenus Kouphichnium .The   trackway,   corresponding   to   locomotion   behavior   and   left   bya   26   cmwidespecimen,   can   be   related   to   the   ichnospecies   Kouphichnium   lithographicum .This   is   thefirst   evidence   of    alimulid   from   the   Canjuers   Lagerstätte.©   2013   Académie   des   sciences.   Publié   par   Elsevier   Masson   SAS.   Tous   droits   réservés. Motsclés: CanjuersFrancePisteEmpreintes JurassiqueTithonienLimule Kouphichniumlithographicum r   é   s   u   m   é Nous   décrivons   ici   la   première   dalle   àempreintes   d’invertébré   retrouvée   dans   les   cal-caireslithographiques   du   Lagerstätte   de   Canjuers.   La   piste   visible   àlasurface   de   la   dalle   aune   longueur   de   39   cm,   pour   une   largeur   d’environ   17cm.   Elle   est   formée   de   deux   pairesdeséries   d’empreintes   successives   ainsi   que   du   début   d’une   troisième.   Les   empreintesse   présentent   sous   deux   formes   :les   mieux   préservées   sont   tétradactyles,   alors   que   lestracesintermédiaires,   par   groupes   de   deux   ou   trois   lorsqu’elles   sont   visibles,   sont   finesetallongées.   Les   empreintes   décrites   dans   cet   article   sont   similaires   àcelles   du   spéci-men   type   de   l’ichnogenre   Kouphichnium .La   piste,   assimilée   au   comportement   locomoteurd’un   spécimen   d’environ   26   cmde   large,   peut   être   associée   àl’ichnoespèce   Kouphichniumlithographicum .Ils’agit   de   la   première   mention   d’un   limule   dans   le   Lagerstätte   de   Canjuers.©   2013   Académie   des   sciences.   Publié   par   Elsevier   Masson   SAS.   Tous   droits   réservés. ∗ Correspondingauthor. E-mailaddresses: claire.pdf@gmail.com(C.PeyredeFabrègues),rallain@mnhn.fr(R.Allain). 1631-0683/$–seefrontmatter©2013Académiedessciences.PubliéparElsevierMassonSAS.Tousdroitsréservés.http://dx.doi.org/10.1016/j.crpv.2013.05.009  182 C.PeyredeFabrègues,R.Allain/C.R.Palevol12(2013)181–189 1.Introduction SeveralKonservat-LagerstättenareknownfromtheLateJurassicofEurope,includingCanjuers(Var,France),Cerin(Ain,France),Crayssac(Lot,France),andSolnhofen(Bavaria,Germany).ThelastisprobablythemostfamousbecausetheSolnhofenlithographiclimestonespreservearichassemblageoffossilizedorganismsincludingthe11specimensoftheoldestknownbird,  Archaeopteryxlithographica (Wellnhofer,2009).DuringtheLateJurassic, EuropewasavastarchipelagoandtheKonservat-Lagerstättenlistedaboverepresentmarineorestuarineenvironments(Fig.1).TheTithonianlimestonesofCrayssac representalargelittoralmud-flatwithsedimentationintheinter-tosupratidalarea,whereasmostofthelocalitiesintheSolnhofenarea,andtheCerinandCanjuersLagerstät-tenpreservelagoonalenvironments(Atrops,1994;Bartheletal.,1990;Bernier,1984;Charbonnieretal.,submittedforpublication)(Fig.1).Untilnow,eachofthemhasyielded tracksandtrackwaysofvertebratesand/orinvertebrates.TurtleandlimulidtrackwayshavebeenfoundinCerin(Gaillard,2011;Gaillardetal.,2003),Solnhofenhaspre- servedlimulidandcrustaceantraces(e.g.Barthel,1974;LomaxandRacay,2012;Malz,1964;VallonandRöper,2006),andcrustaceanandlimulidtraceshavebeendiscov-eredatCrayssac(Gaillardetal.,2005),aswellaspterosaur, dinosaur,crocodylomorphandturtletracks(Mazinetal.,1997).Rhynchocephaliantrackwayswerebrieflymen-tionedintheCanjuerslithographiclimestones(Michard,1989)(Fig.1). HerewedescribeandstudythefirsttrackwayfromtheLateJurassiclithographiclimestonesofCanjuers.ThisLagerstätteisfamousfortheskeletonofthesmallcoelurosauriandinosaur Compsognathuslongipes (Peyer,2006)aswellasmanyothervertebratesincludingturtles,pterosaurs,crocodilians,rhynchocephalians,actinoptery-giansandchondrichthyans(Fabreetal.,1982),marine invertebratesincludingechinoderms,brachiopods,crus-taceans,ammonitesandbivalves(RomanandFabre,1986;Romanetal.,1991),andplants(Romanetal.,1994). 2.MaterialandbriefintroductiontotheCanjuersLagerstätte  2.1.Originofthestudiedslab Theoriginalslabwas   discoveredduringthe1970samongabatchoflargeslabs(DallesdeProvence)soldbyquarry-workersforpaving.Later,itwas   soldbythefirstownertoMr   Guy,whograciouslyloanedtheslabtotheMuséumnationald’histoirenaturelle(MNHN)inParis,inordertocastandstudyit.ThesrcinalslabisatthemomentinasmallFrenchmuseum,thePréhistoramadeRousson,intheDepartmentofGard(cataloguenumber:MPR1).Unfor-tunately,some40yearsafteritsdiscovery,itisimpossibletofindoutwheretheslabcomesfromwithcertainty.Nev-ertheless,themainquarryofCanjuerswasexploitedduringthe1970sfortheDallesdeProvenceandtheformerownersoftheslabstatedtoMr   Guythatitcamefromthissite.Thereisnoreasontodoubtthistestimony.Moreover,thesedi-mentologicalfeaturesoftheslabfitperfectlywithotherslabsstoredattheMNHN.Theoriginalslabpreservedthenegativeimprintofatrackwaycomposedof18individualtracks(Figs.2and3).ItwascastattheMNHNinordertoobtainthecounterpartoftheslabandstudythepositiveimprintofthetrackway(Fig.4).Thetrackmakerhadbeenfirstconsideredapterosaurbasedonthemainimprints.But,giventhepresenceof intermediatetracks,thesecondhypothesisestablishing Fig.1. a:mainLateJurassicLagerstättenfromwesternEuropewithtracksfoundineachoneandtheirenvironmentfunctionsoftime(modifiedfromMazinet   al.,1997);b:locationofCanjuersinLateJurassicpaleogeography(150Ma)   (modifiedfromhttp://cpgeosystems.com). Fig.1. a:principauxLagerstättenduJurassiquesupérieurd’Europeoccidentale,aveclesempreintestrouvéesdanschacund’euxetleurenvironnementen   fonctiondutemps(modifiéd’aprèsMazinetal.,1997);b:localisationdeCanjuersdanslapaléogéographieduJurassiquesupérieur(150Ma),(modifié d’aprèshttp://cpgeosystems.com).  C.PeyredeFabrègues,R.Allain/C.R.Palevol12(2013)181–189 183 Fig.2. Originaltrackwayof  Kouphichniumlithographicum fromtheLate JurassicofCanjuers.Scalebar=10cm. Fig.2. Pisteoriginalede Kouphichniumlithographicum duJurassiquesupérieurdeCanjuers.Barred’échelle=10cm. alimulidasthetrackmakerwasmorecongruentwithourobservations.Inthepast,limulidtrackshavealreadybeenmistakenforbirdorpterosaurtracks(Lockleyetal.,2008;Wellnhofer,1991).Moreover,thetrackwayfromCanjuersisverysimilartoonerecentlydescribedfromCerin(Gaillard,2011).  2.2.LocationandbriefhistoricalintroductiontotheCanjuersLagerstätte TheCanjuersLagerstätteislocatedinthemilitarycampofCanjuers,insoutheasternFrance,intheHaute-Provenceregion,morepreciselyintheDepartmentofVar,nearthevillageofComps-sur-Artuby.TheCanjuerslithographiclimestoneswerefirstexploitedinthelate1960sbyseveralfamiliesofquarry-workerstoproduceornamentalstonescalled“DallesdeProvence”(seeabove).Thecommercialexploitationcontinueduntiltheearly1970swhenCan- juerswas   declaredamilitarycamp.Fortunately,accesstothesitebythescientificcommunitywasstillgranted.Thefirstscientificstudiesofthelocalitydatebacktothe1970s(GinsburgandMennessier,1970).Untiltheearly1980s,J. FabreledtheexcavationsatCanjuers(Fabreetal.,1982).Duringthe1980s,theGhirardifamilysoldtheircollectionoffossils,includingthesmalldinosaur Compsognathus ,totheMNHN.From1983to1993,paleontologistsfromtheParisMuseumexcavatedthesiteexclusivelyduringthesummer;theseexcavationsresultedinthediscoveryof newfossils(deBroin,1994;Poyato-ArizaandWenz,1994).Fromthemid-ninetiesto2004,paleontologistscancelledfieldtripstotheCanjuersLagerstätte.In2010and2011,twogeologicalfieldseasonspermittedafullerunderstand-ingofthegeology,sedimentology,andpaleoenvironmentalhistoryofthesite(Charbonnieretal.,unpublisheddata).  2.3.Localgeologicalcontext  ThetenquarriesofCanjuersthathaveyieldedfossilsarelocatedinasingleareacalled“LesBessons”,whichcoversasurfaceofmorethan15ha.Theoutcropiscomposedof threedistinctlithologicalunits.Thereare,fromthebasetothetop,lithographiclimestones,bioclasticlimestonesandsublithographiclimestones.Onlythebasalunit,character-izedbyalternationsofthinlithographiclimestonebeds,correspondstotheCanjuersKonservat-Lagerstätte(Char-bonnieretal.,unpublisheddata).Thecompositionofthelithographicbedsindicatesthatthedifferentunitsweredepositedduringdifferenthydrodynamiccycleswithinthelagoon.Indeed,thelagoon’swaterwasevaporatingorrefillingdependingontheconnectionwiththeopensea.Thisconnectionwas   basedonenvironmentalconditions.Sometimesacompleteruptureofthislinkcausedthedry-ingofthelagoon.Hence,theexceptionalpreservationof thefossilizedorganismswas   favored,aboveallifmicrobial Fig.3. Drawingofthewholetrackwayshowingthesetsofimprintsandtheirdesignation.Thearrowindicatesthedirectionofmovement.Notatscale.PL:left   pusher,PR:rightpusher,LL:leftleg,LR:rightleg. Fig.3. Dessindelapisteentière,montranttouslesensemblesd’empreintesetleurdénomination.Laflècheindiquelesensdudéplacement.Nonàl’échelle.PL    :empreinteprincipalegauche,PR:empreinteprincipaledroite,LL:appendicegauche,LR:appendicedroit.  184 C.PeyredeFabrègues,R.Allain/C.R.Palevol12(2013)181–189 Fig.4. Mainmeasurementsmadeontheslab:a:apartofthetrackway(positiveimprints)andmeasurementsassociated;b:detailofamain“pusher”imprint   (positive)andmeasurementsassociated;c:detailofamainandanintermediateimprints(negative)ontheoriginalslab.EW:   externalwidth,IW:internalwidth,S:series,RD:repeatdistance,w:width,l:length,A:angle.Scalebar=5cm. Fig.4. a:principalesmesuresréaliséessurlapiste(empreintes);b:détaild’uneempreinteprincipale(empreinte);c:détaild’uneempreinteprincipaleet   d’uneintermédiairesurladalleoriginale(contre-empreintes).EW:largeurexterne,IW:largeurinterne,S:série,RD:enjambée,w:largeur,l:longueur,A   :angle.Barred’échelle=5cm. matswerelaiddown(Atrops,1994).Theorganismsfound inthelithographiclimestonesareeitherfrommarineorcontinentalenvironments. 3.Methods  3.1.Measurements Thefirstobservationsweredonebythenakedeyeinordertoobservethemaincharacteristicsofthetrackwaysuchasthealignmentandthedispositionofthetracks.Thenweusedthemethodologiesproposedforlocomotiontracesofarthropods(Gaillard,2011;Trewin,1994)inorder tocarryoutprecisemeasurementsonthewholetrack-way.We   firstevaluatedtheexternal(EW)andinternal(IW)widthsofthetrackway,whichweremeasuredbetweeneachpairofmaintracksandcorrespondtothemaximumandminimumwidthofthetrackway.We   estimatedthelengthofeachseries(S)ofimprints.Oneseriesiscomposedofamainimprintandthethreefollowingintermediateimprintsfoundonthesamesideofthetrackway.Thestridewasalsomeasured;itcorrespondstotherepeatdistance(RD),itmeansthelengthbetweentwosetsofimprints.Thewidth(w)andlength(l)ofeachmainimprintwereevaluated.Concerningtheintermediatetracks,we   onlyestimatedthelength.Finally,thevalueoftheangle(A)tomid-linewasmeasured(Fig.4).Allthemeasurementswere madetwiceusingarulergraduatedinmillimeters.Inordertochecksomeofthem,weusedthesoftwareMesurim(Madre,1998–2011)ondigitalpicturesoftheslab. 4.SystematicPaleontology  Ichnogenus Kouphichnium Nopsca,1923Diagnosis(followingHäntzschel,1975,p.W75).Het- eropodoustracksofgreatvariability;complextrackconsistingoftwokindsofimprints:(1)two   chevron-likeserieseachoffourovalorroundholesorbifidV-shapedimpressionsorscratches,forwardlydirected(madebyanteriorfourpairsoffeet);and(2)onepairofdigitateorflabellar,toe-shapedorotherwisevariableimprints(madebybird-footlike‘pushers’offifthpairoffeet,withtheirfourorfiveleaf-likemovableblades);trackwithorwithoutmediandragmark.Ichnospecies Kouphichniumlithographicum Oppel,1862Diagnosis.Thisichnospecieswas   firstproposedforsim-plestraightlocomotiontracesfoundintheSolnhofenarea.TheslabfromtheCanjuerslithographiclimestonesexhibitsasimple,straighttrackwayandwasthusassignedto K.lithographicum . 5.Description 5.1.Trackwaymorphology Thepreservedpartofthetrackwayissymmetrical,straightand39cmlong.Itrepresentstwocompletesetsofimprintsandthebeginningofathirdone.Thetwofirstsetsshowtwowell-preservedmainimprintsandtwo   or  C.PeyredeFabrègues,R.Allain/C.R.Palevol12(2013)181–189 185  Table   1 Measurementsonthetrackway.External(EW)andinternal(IW)widthof thetrackway,series(S)length,repeatdistance(RD)andangles(A)withthe   medianaxisofthetrackway.PL:pusherleft,PR:pusherright,SL:seriesleft,   SR:seriesright.  Tableau1 Mesuresréaliséessurlapiste.Largeursexterne(EW)etinterne(IW),longueursdesséries(S),enjambées(RD)etangles(A)parrapportàl’axemédiandelapiste.PL:empreinteprincipalegauche,PR:empreinteprin-cipaledroite,SL:sériegauche,SR:sériedroite.EW(mm)   IW(mm)PL1–PR1172119PL2   –PR2178123PL3   –PR3?122Mean175121S   (mm)LeftSL1181SL2182RightSR1178SR2?Mean180.3RD(mm)LeftPL1–PL2177PL2–PL3181RightPR1–PR2175PR2–PR3 ?Mean177.7A   (degrees)LeftSL1–SL214SL2–SL316RightSR1–SR212SR2–SR3 13Mean13.75 threeintermediateimprints.Thethirdsetislocatedattheendoftheslabandonlypreservesmainimprints(inter-mediatearenotvisible);theoneontherightisdamagedattheextremity.Nomedianimprintwasobservedonthetrackway,whichmeansthatthelimulid’stelsonwasnotincontactwiththesubstrateduringitsmotion(Fig.3). Themeanoftheexternalwidthofthetrackwayis175mmandthemeanoftheinternalwidthis121mm.   Theaverageserieslengthis180mm(SL1correspondstothedistancebetweenPL1andLL1-III,SL2isfromPL2toLL2-III,thesamefortherightside).Themeanstrideis178mm.   Theangletothemid-linewasmeasuredinthefourcases;itsmeanis13.75 ◦ (Table1). 5.2.Mainimprints Themainimprintsofthetrackwayarethemostexternalones.Ineachset,twoofthemaresymmetricallyopposed:theycorrespondtotheimprintleftbythesixthpairof legs.Thesetracksaretriangular-shaped:theiranteriorpart  Table2 Measurementsontheimprints.Length( l )andwidth( w )ofthepusherimprints(legsVI)andlength( L )oftheintermediateimprints(legsIII,IVandV),leftandright.PL:leftpusher,PR:rightpusher,LL:leftleg,LR:rightleg.  Tableau2 Mesuresréaliséessurlesempreintes.Longueur( l )etlargeur( w )desempreintesprincipales(appendicesVI)etlongueur( L )desempreintesintermédiaires(appendicesIII,IVetV),gauchesetdroites.PL:empreinteprincipalegauche,PR:empreinteprincipaledroite,LL:appendicegauche,LR    :appendicedroit.Pushers l (mm)  w (mm) Legs L (mm)LeftPL12825LL0–III18PL22726LL1–V19PL32926LL1–IV17LL1–III9LL2–V15LL2–IV15LL2–III12Mean28.025.7Mean15RightPR13125LR0–III14PR23126LR1–V15PR3??LR1–IV16LR1–III?LR2–V 18LR2–IV10LR2–III?Mean31.025.5MeanG istetradactylwhereastheposteriorpartisnarrowerandbifid.Theyaretheresultofthecontactbetweenthesub-strateandtheextremityofthesixthpairoflegs,whichleadstotheflatteningoftheirfiveindividualpieces:fourpiecesspreadingontheanteriorpartoftheextremityandthefifth,whichisbifidattheend,restoringthebalanceontheposteriorpart.Thesiximprintsshowequivalentproportions.Onaverage,imprintsmadebytheleftlegVI(PL)are28mmlongand25.7mmwide.ThoseoftherightlegVI(PR)are31mmlongandtheirwidthis25.5mm(Table2). 5.3.Intermediateimprints Thesevaryinnumber:twoorthreeareineachset.Amongthem,twoarefine,elongateandsingle:theyaretheimprintsofappendagesIVandV.Theothertypeisslightlythickeranddouble:itisthemarkofthethirdappendages,thefirstwalkinglegs.ThemarksofappendagesIVandVareinsertedbetweentwomainimprints,andmoreinter-nalthanthelatter.Theyarestraightandslightlyobliquebecausetheiranteriorpartpointstothemedianaxisof thetrackway.TracksofappendagesIIIarelocatednexttothemainimprints,ontheirinnerside.Twoimprintsdonotappearonthetrackway:LR1–IIIandLR2–III.AppendageIIIdoesnotalwayscontactthesubstrate,probablybecauseoftheirsmallsizeorbecausewearedealingwithundertracks(GoldringandSeilacher,1971).Thelatterhypothesisisneverthelessunlikelybecausethepreservationofimprintsoftheotherappendagesisgood.Onaverage,intermediateimprintsare15mmlongontheleftand14.6mmlongontherightofthetrackway(Table2).
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