Late Cretaceous nodosaurids (Ankylosauria: Ornithischia - SciELO
Transcript of Late Cretaceous nodosaurids (Ankylosauria: Ornithischia - SciELO
Late Cretaceous nodosaurids (Ankylosauria: Ornithischia) from Mexico 371
ABSTRACT
Nodosaurid ankylosaur remains from the Upper Cretaceous of Mexico are summarized. The specimens are from the El Gallo Formation of Baja California, the Pen and Aguja Formations of northwestern Coahuila, and the Cerro del Pueblo Formation of southeast Coahuila, Mexico. These specimens show differences from other known nodosaurids, including an ulna with a well developed olecranon and prominent humeral notch, the distal end of the femur not flaring to the extent seen in other nodosaurids, and a horn-like spine with vascular grooves on one side. The specimens represent the southernmost occurrences of nodosaur remains in North America, and provide an important biogeographical link between nodosaurids of the United States and Canada on the one hand, and Argentina and Antarctica on the other.
Key words: nodosaurid, Ankylosauria, Late Cretaceous, Baja California, Coahuila, Mexico.
RESUMEN
Restos de anquilosaurios nodosáuridos del Cretácico Superior de México son descritos aquí. Las muestras proceden de la Formación El Gallo de Baja California, de las formaciones Pen y Aguja del noroeste de Coahuila, y de la Formación Cerro del Pueblo, sureste de Coahuila, México. Estas muestras presentaron diferencias significativas con otros nodosáuridos conocidos, incluyendo el cúbito con olécranon bien desarrollado y la muesca del húmero prominente, el extremo distal del fémur de diferente medida no visto en otros nodosáuridos, y una espina similar a un cuerno con los surcos vasculares en un lado. Las muestras son importantes porque son los hallazgos más meridionales de América del Norte, y proporcionan un vínculo biogeográfico importante entre los nodosáuridos de los Estados Unidos y Canadá, por un lado, y Argentina y la Antártida por el otro.
Palabras clave: nodosáurido, Anquilosaurio, Cretácico Tardío, Baja California, Coahuila, México.
LateCretaceousnodosaurids(Ankylosauria:Ornithischia)fromMexico
Héctor E. Rivera-Sylva1,*, Kenneth Carpenter2,3, and Francisco Javier Aranda-Manteca4
1 Departamento de Paleontología, Museo del Desierto, Carlos Abedrop Dávila 3745, 25022, Saltillo, Coahuila, Mexico.
2 Prehistoric Museum, Utah State University – College of Eastern Utah, 155 East main Street, Price, 84501 Utah, USA. 3 University of Colorado Museum, 80309 Boulder, Colorado, USA.
4 Laboratorio de Paleontología, Facultad de Ciencias Marinas, Universidad Autónoma de Baja California, Ensenada, Baja California, Mexico.
Revista Mexicana de Ciencias Geológicas, v. 28, núm. 3, 2011, p. 371-378
Rivera-Sylva,H.E.,Carpenter,K.,Aranda-Manteca,F.J.,2011,LateCretaceousnodosaurids(Ankylosauria:Ornithischia)fromMexico:RevistaMexicanadeCienciasGeológicas,v.28,núm.3,p.371-378.
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INTRODUCTION
Nodosauridankylosaursformanimportantcompo-nentoftheLateCretaceousdinosaurfaunainthenorthernhemisphere,especiallyEurope, theUnitedStates,andCanada(Coombs,1978;Carpenter,2001).Recently,how-ever,nodosauridshavebeenreportedfromthesouthernhemisphere,includingArgentina(CoriaandSalgado,2001)andAntarctica(Gaspariniet al.,1987;1996).CrucialtounderstandingthedistributionoftheseankylosaursarespecimensfromMexico.
In 1971, Harley J. Garbani found the first evidence ofanankylosaurfromBajaCalifornia,anosteodermfromElGalloFormation(Campanian).ThespecimenwasonlymentionedbyMorris(1967)andtheosteodermwasheldintheLosAngelesCountyMuseum.LateritwastransferredtotheColecciónNacionaldePaleontologíaintheUniversidadNacionalAutónomadeMéxico(UNAM).Unfortunately,thespecimencannotbelocated(Perrilliat,pers.com.,2009),thusitsidentityasnodosauridorankylosauridremainsun-known.AnewspecimenofankylosaurfromBajaisatoothfromtheElJabóncreeklocality,ElDisecadomember,ElGalloFormation(Campanian),BajaCalifornia,Mexico.In2006,Rivera-SylvaandEspinosa-Chávezreportedthepres-enceofankylosaurosteodermsfromtheCerrodelPuebloFormationinCoahuila,Mexico.Sincethen,additionalun-describedankylosaurremainshavebeenfoundintheUpperCretaceousofMexico(Meyeret al.,2005),includingtwovertebraeandametatarsalfromtheSanCarlosFormation
inAldama,Chihuahua(Figure1).WedescribesomeofthisnewmaterialhereandhighlightdifferenceswithspecimensfromcontemporaneousformationsofthenorthernUnitedStatesandsouthernCanada.Thesedifferencessuggestthatthemexicannodosauridsrepresentatleastonenewtaxon,butatpresentwerefrainfromnamingitowingtothefrag-mentarynatureofthematerial.
Theabbreviationsusedinthisstudyareasfollows:AMNH=AmericanMuseumofNaturalHistory,NewYork,NewYork,USA;CPC=ColecciónPaleontológicadeCoahuila,MuseodelDesierto,Saltillo,Coahuila,Mexico;UABCFCM=UniversidadAutónomadeBajaCaliforniaFacultaddeCienciasMarinas,Ensenada,BajaCalifornia,Mexico.
SYSTEMATIC PALAEONTOLOGY
SuborderThyreophoraNopcsa,1915InfraorderAnkylosauriaOsborn,1923
FamilyNodosauridaeMarsh,1890Nodosauridaeindet.
Specimen A
Materialexamined.UABCFCM2625,onetoothcrown(Figure2).Occurrence. ThematerialwasrecoveredingreymudstonefromElDisecadoMemberof theElGalloFormation(Campanian),ElJabónravine,BajaCalifornia,Mexico
Figure1.MapofMexicoshowingknownlocalitieswithnodosauridmaterial,1)ElRosario,ElGalloFormation,B.C.;2)Aldama,SanCarlosFormation,Chihuahua;3)LaSalada,AgujaFormation,Coahuila;4)SanMiguel,PenFormation,Coahuila;5)ElPelillal,CerrodelPuebloFormation,Coahuila.
Late Cretaceous nodosaurids (Ankylosauria: Ornithischia) from Mexico 373
cross-section.Thedistalcondylesarewellpreserved,andbothareaboutequalinsize,althoughthemedialcondyleextendsventrallybeyondthelateralcondyle.Incontrast,inbothEdmontoniaandPanoplosaurus themedialcondyleissmallerthanthelateralcondyleanddoesnotextendventrallyverymuchbeyondthelateralcondyle.
Theleftulnalacksthedistalthird(Figure3i-3l).TheolecranonismostsimilartothatofStegopelta(CarpenterandKirkland,1998)inthatitisaprominent,nearlyparallel-sidedforminlateralviewandistruncatedproximally;thisisincontrasttothemoreusualtaperingorconicalprocessinmanyankylosaurs(Carpenter,pers.obs).Inanteriorview,theolecranonresemblesthatofmostankylosaurs,beingabroad,invertedrighttriangle.However,theproximalendisrounded,ratherthantaperedasinSauropelta. Thehumeralnotchatthebaseoftheolecranoniswelldeveloped,whereasthelaterallyplacedradialnotchisshallowasistypicalofankylosaurs(Carpenter,pers.obs).
Theleftfemurisrepresentedbythedistalthird.Theintercondylargrooveisshallow.Thedistalendisslightlywiderthantheshaft(Figure3),whereasinEdmontonia,the distal end flares significantly wider than the shaft (the femurisunknowninPanoplosaurus).Posteriorly,thelateralcondylar ridge (sometimes referred to as the fibular process), issquareandprominent.
Along,tapered,slightlycurved“horn”-likestructureisprobablyadistalthoracicosteodermthatismissingitsbase(Figure3m-3p).Incross-section,theosteodermisel-liptical,beingdeeperthanwide.Oneside(anterior?)hasvasculargroovesextendingthelengthofthebone,thussomewhatresemblingaceratopsianhorn-core.
Specimen C
Material examined.CPC273consistsoftwocaudalverte-bra(CPC273/1;CPC273/2),onecervicalrib(CPC273/3),sixribfragments(CPC273/4),aposteriorfragmentofilium(CPC273/5),proximalfragmentof?tibia(CPC273/6),proximalendof?femur(CPC273/7);thirteenosteoderms
(N30º03’14”;W115º45’44”)(Figure1).Description.Thespecimenconsistsofa toothcrownlackingtheroot.Itmostcloselyresemblesthoseofothernodosauridsinitsrelativelylargesize,presenceofacom-pleteshelf-likecingulum,andlowdenticlecountalongthemargins(6anteriorlyand3posteriorly).Thecingulumisirregularonthelabialside,whereasonthelingualsideitissmoothandconcave.
Teetharetaxonomicallyusefulatthefamilylevelinankylosaurs(CoombsandMaryanska,1990).Toothcrownsofnodosauridsareproportionallylarge,withfewdenticles(4-8)alongthemarginsthatinmostcasesextendontothecrownfaceasridges(Coombs,1990).Thebaseofthecrownisswollenandacompletecingulumispresentononeorbothsides.Incontrast,theteethofpolacanthidsandanky-losauridsaresmall(Carpenter,pers.obs.,2001).
Specimen B
Material examined.CPC272,onedorsalvertebra,onecaudalvertebra,distalendofhumerus,partialulna,distalendoffemur,oneribfragment,andoneosteodermalspine(Figure3).Occurrence. ThematerialwasrecoveredfromtheshaleofthemarinememberofthePenFormation(Campanian),southofSanMiguel,Coahuila,Mexico(N28º38’16”;W102º56’55”)(Figure1).Description.Thedorsalvertebraconsistsprimarilyofthecentrum(Figure3e-3h).Ithasatypicalankylosaurianmor-phology,beingamphiplatyan,spool-shapedandconstrictedinthemiddle;itislongerandtallerthanwide.Aportionofonepeduncleispresent,butotherwisetheneuralarchandspinearemissing.Thecaudalvertebraconsistsonlyofadamagedcentrum,withtheneuralarchandspinemissing.Thecentrumisanteroposteriorlyshorterthanwide,andsomewhathexagonalinproximalview,asinmanynodo-saurids(Carpenter,pers.obs.).
Thelefthumerusconsistsofthedistalend(Figure3a-3d).Theincompleteshaftismediolaterallyellipticalin
Figure2.UABCFCM2625,nodosauridtoothfromBajaCalifornia,Mexico,in(a)labial,(b)lingual,(c)cranial,and(d)distalviews.Theocclusalsurfaceisup.Scalebar=5mm.
a) b) c) d)
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Figure3.CPC272,nodosauridelementsfromCoahuila,Mexico.Distalendofrighthumerusin(a)dorsal,(b)ventral,(c)anterior,and(d)posteriorviews;dorsalvertebrain(e)cranial,(f)caudal,and(g-h)lateralviews;rightulnain(i)dorsal,(j)ventral,and(k-l)lateralviews;osteodermalspine(m-p).Scalebar=5cm.
a) b)
c)
d)
e) f)
g) h)
i) j)
m)
n)
o)
p)
k) l)
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Figure 4. CPC 273, nodosaurid elements from Coahuila, Mexico, in superficial view. Dorsal osteoderms CPC 273/13-15 (a-c); fragment of ?thoracic osteodermCPC273/18(d);ossicleCPC273/19(e);distalosteodermCPC273/16(f);medialcervicalosteodermsCPC273/8-9(g,h);osteodermalspine(i).Scalebar=5cm.
(CPC273/9;CPC273/10;CPC273/11;CPC273/12;CPC273/13;CPC273/14;CPC273/15;CPC273/16;CPC273/17;CPC273/18;CPC273/19;CPC273/20;CPC273/21;CPC273/22),proximalendofscapula(CPC273/23),andtwentysevenundeterminedbonefragments(CPC273/24)(Figure4,Table1).Occurrence. ThematerialwasrecoveredinsandymudstonelayersfromthetheupperunnamedmemberoftheAgujaFormation(Campanian),westoftheElCarricito,townshipofOcampo,Coahuila,Mexico(N28º55’17”;W103º19’72”)(Figure1).Description.Thevertebraeandthetibiawerecollectedfromthesamesiteastheosteodermsandthesearethereforeassumedtobelongtothesameindividual.
Vertebrae.CPC273/1isacaudalvertebra,bearingfacetsforribarticulation.Theneuralcanaliscircularandbrokendorsally.Theneuralspineisbroken.Theventralsurfaceisweathered.Incontrast,CPC273/2hasashorttransverseprocess.Mostofthesurfaceofthecentrumiseroded;thereisaforamenonitsventralsurface.
Tibia.Apartialrighttibiaisrepresentedbytheproxi-malend.Ithasashortcnemialcrestlocatednearthemedialedge.Thelateralsideismissing,thustherelativewidthversuslengthofthetibialplateaucannotbedetermined.
Ilium.Aroundedfragmentmaybethepostacetabularprocessoftherightilium.Thedorsalsurfaceisslightly
concave,whereastheventralsidehasaroundedreinforcingridgeorbuttressthatextendsthelengthofthefragment.ItsdistalterminationisbluntandmayhavebeentheoriginoftheM.caudofemoralis brevis.Thisridgeisoffsettowardsthemedialhalf.Thepreservedportionistooincompleteforcomparisonwithotherilia.
Scapula.Thescapulaisrepresentedbythescapularmarginoftheglenoidcavity.Theangleoftheglenoidsug-gestsitisaleftscapula.Unfortunately,itdoesnotpreservethedorsalmarginoracromionprocess.
Osteoderms.CPC273/9(Figure4g)is largeandrectangular,withamediankeelthatistallerposteriorlyandterminatesinaconicalpointneartheosteoderm’sposteriormargin;itslateralmarginisbroken.CPC273/10andCPC273/11havethesameanatomicalfeaturesasCPC273/9butbotharebrokenintheirmiddles.CPC273/12isaconicalanterolaterally-directedcervicalspine(Figure4i).CPC273/13,CPC273/14,andCPC273/15arecircularwithalowkeelandareofthetypefoundinthethoracicregionofEdmontonia(Carpenter,1990)(Figure4a-4c).CPC273/16isadistalthoracicosteoderm.CPC273/17isacaudalosteoderm.CPC273/19isacircularossicle(Figure4e).The superficial surface is flat; the deep surface is flat to slightly concave. The superficial surface is pitted, grooved, andrugose.Themarginisrounded.
CPC273canbeattributedtotheNodosauridaebased
a) b)c)
d) e)
f) g)
h)i)
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ontheanterolaterally-directeddistalcervicalspineandthekeeledthoracicosteodermsthatareslightlyexcavatedontheirdeepsurface(Vickaryouset al.,2004; Lee,1996;Sereno, 1986). The superficial surface texture of the osteo-dermsmostcloselymatchesthatreportedbyBurns(2008)forGlyptodontopeltainthatthesurfaceisgenerallysmooth,butthereareafewrandomlydistributedsmallpitsandvasculargroovesthatradiatefromthekeel.Thesediffer,however,inthatthepittingislessextensive.
Specimen D
Material examined.CPC275,caudalvertebra.Occurrence. Thematerialwasrecoveredfromsandstonelay-ersfromtheCerrodelPuebloFormation(Campanian),northofSaltillo,Coahuila,Mexico(N26º10’48”;W101º16’48”).(Figure1).Description.CPC275isacaudalvertebraerodedonmostofitssurface.Itconsistsofacentrumlackingmostoftheneuralarchandspine,andthetransverseprocess.Thecentrumisshortanteroposteriorlyandhasapairofchevronfacetsontheposteroventraledge.Inposteriorview,thecentrumhasthecharacteristichexagonalshapeofanodosaurid.
DISCUSSION
Thetooth(UABCFCM2625)issimilartothatofAletopelta coombsi(FordandKirkland,2001)fromtheUpperCretaceousofsouthernCalifornia.FordandKirkland(2001)considerAletopelta tobeanankylosauridandnotanodosauridasoriginallydescribedbyCoombsandDemere(1996).However,Aletopeltaalsohasnodosauridcharactersincludingtoothmorphologyandosteodermsthatarethickerthanthoseoftypicalankylosaurids(Carpenter,pers.obs.).
ThespecimenCPC273isanodosauridbecausetheosteodermsarethickandhaveaslightlyconcavebase.CPC272 is also identified as a nodosaurid primarily because of theelongateosteodermalspine.
Although four nodosaurids have thus far beenidentified from the Upper Cretaceous of North America (Panoplosaurus,Edmontonia,Glyptodontopelta,andAletopelta),specimenBfromthePenFormationsuggeststhe presence of a fifth genus (Table 2). However, the mate-rialistoofragmentarytobenamed.
OsteodermsrepresentthemostabundantmaterialamongtheMexicanspecimens.CPC273/12issimilartothedistal osteoderm of the first cervical ring (Sternberg, 1928), somewhatlikethatprojectinganterolaterallyfromthecervi-calhalfringsofAMNH5665(Edmontonia;Matthew,1922;Carpenter,1990).Theoval,lowkeeledosteodermissimilartothelateralcervicalosteodermsillustratedforEdmontonia(Carpenter,1997),CPC273,andAMNH5665.However,thesurfacetextureisdifferentfromEdmontonia(Table2)inthatithaspittingandadentriticpatternradiatingfromthekeel(Burns,2008).
Lehman(1997)estimatedthatankylosaurscom-prisedonly8%ofthedinosaurfaunainthenearbyAgujaFormationintheBigBendregionofTexas.BasedonNorthAmericanlocalitiesofankylosaurtracksites(McCreaet al.,2001)andthepresenceofaquaticvertebratesassociatedwithankylosaurbonesandteeth,ankylosaursprobablypreferredhumidenvironments(Vickaryouset al.,2004).
However,manyAsianankylosaurslivedinaridorsemi-aridenvironments(Carpenter,1997)andtheirrarityin the Aguja Formation and other coastal and floodplain set-tings,suchastheCerrodelPuebloFormation,mayindicatethattheyweremorecommonininlandareasthatarenotwelldocumentedintheNorthAmericanfossilrecord.
CONCLUSIONS
ThediscoveryofnodosauridremainsintheUpperCretaceousofMexicoisnotunexpected.ThesearethesouthernmostoccurrencesofthefamilyinNorthAmerica.Twogeneraofnodosauridankylosaurshavebeenre-portedfromtheCampanianAgujaFormationofTexas,Panoplosaurussp.andEdmontoniasp.(Lehman,1987;Carpenter,1990;Weishampelet al.,2004;Vickaryouset
Specimen number
Bone Maximum length
Maximum height
Maximum width
CPC273/1 Vertebra 45 59 69
CPC273/2 Vertebra 57 61 80
CPC273/3 Cervicalrib 34 14 23
CPC273/5 Ilium 93 57 101
CPC273/23 Scapula 172 83 124
CPC273/6 ?Tibia 98 88 55
CPC273/7 ?Femur 107 66 92
CPC273/8 Osteoderm 76 35 93
CPC273/9 Osteoderm 112 29 70
CPC273/10 Osteoderm 47 28 59
CPC273/12 Osteoderm 109 52 73
CPC273/13 Osteoderm 81 21 68
CPC273/14 Osteoderm 60 18 41
CPC273/15 Osteoderm 85 31 77
CPC273/16 Osteoderm 120 35 47
CPC273/17 Osteoderm 110 75 59
CPC273/18 Osteoderm 44 34 58
CPC273/19 Osteoderm 40 14 33
CPC273/20 Osteoderm 52 16 57
CPC273/21 Osteoderm 71 31 39
CPC273/22 Osteoderm 78 28 38
Table1.Measurements(inmillimeters)ofCPC273.
Late Cretaceous nodosaurids (Ankylosauria: Ornithischia) from Mexico 377
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al.,2004;Sankey,2010).TheremainsfromMexicomayrepresentone,both,oranewgenus.CPC275alsorepre-sents the first record of a nodosaurid from the Cerro del PuebloFormation.
ACKNOWLEDGEMENTS
Wearegratefultothefollowingindividualsfortheircontributiontothisproject:JoséManuelPadilla,AbrahamIsaíOyervidezSalazar,andJoséLópez,fromtheMuseodelDesierto.IleanadelaPeñaOviedo,JorgeA.OrtízMendieta,RubénGuzmánGutiérrez(SMA),ElizabethJardón,TatianaSánchezRodríguez(MHN),andHomeroHernández helped during field seasons. The Museo del Desiertoisalsothankedforsupportingthisinvestigation,andthereforeweappreciateArturoH.GonzálezGonzálezforhissupportofthisproject.WeareobligedtothankDanielPosadaMartínez(MUDE)forthedonationofSpecimenD.Inthesamemannerwewishtoextendouracknowledge-mentstotheauthoritiesofOcampoandthepeopleofSanMiguelfortheirkindassistanceandsupportforthisproject.WeareindebtedtoFranciscoPalomino,RafaelRodríguezandEdgarGuzmán(nowretired)fromINEGIandtotheinstitutionsandindividualsinvolvedinmanywaystothesuccessofthisproject.
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Taxon Thoracic osteoderm shape Superficial surface texture Keel
Panoplosaurus Elliptical,longerthanwide Highlypitted,producingslighttomoderatelyrugosetexture.
Edmontonia Elliptical,widerthanlong SmootherthanPanoplosaurus.Dendriticvasculargrooves.
Prominent,morelaterally-directed,originatesfromthemedialmarginextendsposteriorlytowardsthelateralmargin.
CPC273 Elliptical,widerthanlong Smoothsurfacetexture.Dendriticvasculargrooves.
Table2.Comparisonofnodosauridarmor.
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Manuscriptreceived:February15,2011Correctedmanuscriptreceived:April15,2011Manuscriptaccepted:May9,2011