sign in sign up
<<
Home , Ectenosaurus, Fox Hills Formation, Lewis Shale, Mosasaur, Mosasaurus, Platecarpus

(1974)recently reported a number of ammo- nites and other invertebratesfrom the Lewis A mosasaurfrom the Shale along the easternedge of the . UNM-V-070 is southeastof their lo- (UpperGretaceous), northwestern cality D4l5l and northeastof their locality D5067. Both D4l5l and D5087 are strati- graphically higher in the Lewis Shale than NewMexico Uf.ftU-V-OZOand are placed by Cobban and History,Yale University' others (1974) in the Late Didy- by'NewHaven,CT,andPeterK.Reser,OiiartmentotAnthropology,University0fNewMexico,Albuquerque,NMSpencer G Lucas,Department of Geology and Geophysics and Peabody Museum of Natural mocerascheyennense ammonite zone. Prob- ably UNM-V-070 is Late Campanianin age (no older strata are known in the Lewis Shale) Mosasaursare an extinct group of giant The following abbreviationsare usedin the (Cobban and others, 1974)and older than the a marinelizards that flourishedduring the Late text: AMNH-Department of VertebratePa- D. cheyennense zone. Unfortunately, out- . Their fossilized remains are leontology, American Museum of Natural diligent searchof the limited Lewis Shale yielded un- known from all the continentsexcept Antarc- History, New York; UNM-Department of crops around UNM-V-070 only tica; the largestand best known collections Geology,University of New , Albu- diagnostic fragments of inoceramid shells; precisely come from the in Kan- querque;YPM-Peabody Museumof Natural hence,its age cannot be more deter- sas. Although marine sediments of Late History,Yale University, New Haven. mined. cretaceousage are exposedthroughout large areas of , only three LewisShale and its fauna specimenshave previously been reported from The Lewis Shale was named by Cross and the state. These specimenswere found in others (1899) for exposuresaround Fort south-centralNew Mexico in the Jornadadel Lewis,an old army post in the La Plata River Muerto region (Cope, l87la) and in north- valleyin southwestColorado. Primarily com- easternNew Mexico in the RatonMesa region posedof dark-grayto greenish-grayshale with (Lee, l9l7'). Late Cretaceousmarine deposits somesandy layers, , and calcareous in otherparts of New Mexico,including exten- nodules,the Lewis Shale has been mapped sive exposuresof the Lewis Shale in and throughouta largearea in northwesternNew aroundthe SanJuan Basin, until recentlyhave Mexico and southwesternColorado (Reeside' failed to produce mosasaur remains. The 1924; Dane, 1936; O'Sullivan and others, discoveryof a mosasaurin the LewisShale as 1972).The Lewis Shale was deposited offshore reported herein is the fourth report of a in the regressingseaway that covered this mosasaurfrom New Mexico (fig. l) and the regionduring the (Fassett and FIGURE2-VIEw oFExcAvATEDMoSASAURREMAINS pointing poste- first report of a mosasaurfrom the Lewis Hinds,l97l; Mannhard,1976). m UNM-V-070;the man is at the portionof thevertebral Shale.This discoveryextends the geographic The faunaof the LewisShale is mainly a di- riorend of thearticulated rangeof the mosasaursinto that part of the verseassemblage of marine bivalves,gastro- column. sea that coverednorthwestern New Mexico pods,and (Reeside, 1924; Dane, duringthe LateCretaceous. 1936:Cobban and others, 1974;Mannhard' DlscusstoN-The taxonomyof , 1976).Worm burrows and other trace like many groupsof ,is basedheavily t07'oo' (for example,Ophiomorpha) also arepresent. on cranial characters(Russell, 1967). The The only vertebratespreviously reported from absenceof any cranialremains of UNM-LK-l ArriboCounty the LewisShale are 's teeth (for example, Rio than jaw and tooth fragmentsthus ren- Lamna sp.) and bony scales(Mannhard, other I ders difficult a preciseidentification of the i t976). I specimen.Fortunately, subfamilies and tribes can be diagnosedlargely on the i SystematicpaleontologY o] mosasaurs basisof vertebralcharacters (Russell, 1967). ClassREPTILIA In addition, the tooth and jaw fragmentsof OrderSAURIA UNM-LK-l aid in a tentativeassessment of FamilyMOSASAURIDAE Gervais, 1853 (Dollo,I 884) its genericidentitY. SubfamilyPLIOPLATECARPINAE justify assign- Williston.1897 The followingconsiderations TribePLIOPLATECARPINI (Dollo' 1884) ment of UNM-LK-l to the Russell,1967 as definedby Russell(1967): l) UNM-LK-I GenusPLATECARPUS CoPe, 1869 was a mosasaurof moderatesize, probably cf. sP. about 6 m in overall length, basedon com- dorsal RBpeR.R.EnspnclneN-UNM-LK-l; a par- parisonof the lengthof its incomplete lengths of tial skeletonconsisting of 46 vertebrae(14 series with vertebral and body various mosasaursgiven by Russell (1967' lVososour dorsals, (?)5 pygals, and 21 caudals) of quorry+o variable preservation,two nearly complete tables 2-3). All plioplatecarpines are (Russell, 1967); thoracic ribs and fragmentsof others, and moderate-sizedmosasaurs all assortedlower(?) jaw andtooth fragments. UNM-LK-l is well within the sizerange of Loc^c.l-trv-UNM-V-070; in the NE'/+ plioplatecarpinespecimens in the YPM collec- SW% sec.9, T. 30N., R. I E. on theJicarilla iions. Althoughundue emphasis should not be Apache Indian Reservation southeast of placedon sizeas a diagnosticcharacter in rep- growth), Dulce,New Mexico(figs. l-2). tiles (animalswith indeterminate no Cot-t-scrons-Originally discovered by evidenceexists to suggestthat UNM-LK-I Adolph Julian and Darrell Paiz, membersof was a particularlyyoung individual;that it is giant the JicarillaApache Indian Tribe; collectedby just a small representativeof one of the like or l-Mlp oF pART oF NoR.THwEsrEnNNrw theauthors. mosasaurs FICURE All caudal vertebraeof Mrxtco sHowINc rHE LocATIoNor UNM-V-070' HoRIZoN nNo ece-In dark-gray fissile seemsunlikely. 2) THEMOSASAUR QUARRY. shaleof the Lewis Shale.Cobban and others ]:F

New Mexico GeologY August l98l 31 UNM-LK-l haveunfused haemal arches (fig. which are small and locatedon the posterior aspectbears numerous thin verticalstriations. 3, C-E). The haemalpeduncles are subcircu- edgeof the baseof the neural arch. The ver- This typeof tooth is typicalof all plioplatecar- lar, centrally pitted, posteroventrallydirected, tebra of this specimenalso closelyresembles pines(Russell,1967). and located near the posterior end of the cen- anterior dorsal vertebrae of Platecarpus AssigningUNM-LK-l asa plioplatecarpine trum lateralto theventral midline. This condi- (Cope,1875, pl. 20, figs. 5M-N). Most of the to ,Pl ioplatecarpus, or Platecar- tion is seenin the plioplatecarpinesbut not in dorsal vertebraeof UNM-LK-I are not as pas is difficult without good cranial material the mosasaurinesin which the haemal pedun- well preservedas this one;typically, the neural preservingthe charactersupon which these cles typically are fused to the caudal centra arch and spineis no longer present.No evi- genera largely are differentiated. Never- (Russell, 1967).3) Other vertebraeof UNM- denceof a zygosphene-zygantrumcan be dis- theless,some slight evidencefrom the post- LK-l correspondwell to thoseof plioplatecar- cernedon any of the vertebrae,but almostall crania argues against assignmentto either pines,although by themselvesthey are not suf- of the vertebraeare so badly damagedthat Ectenosaurus or . Thus, ficient to diagnosethe group. A typical me- ascertainingwhether or not at least a small Russell(1967, p. 158),in his diagnosisof dian dorsal (fig. 3, J-L) has the zygosphene-zygantrumarticulation was pres- Ectenosaurus,noted that its pygal vertebrae synapophysislocated on the anterodorsal ent at somepoint on the dorsalvertebral col- have relativelylong transverseprocesses. In aspectof the centrum, an anterior articular umn is impossible.4) As Russell(1967 , p. 54) contrast,the pygal vertebraeof UNM-LK-I cup that is wider than tall, and a posterior ar- has pointedout, the marginalteeth of mosa- have relatively short transverseprocesses; ticular ball that likewiseis transverselyoval. saurs are "often generically diagnostic." comparisonof two pygalvertebrae with nearly This vertebraclosely resembles median dorsal Among thetooth andjaw fragmentsof UNM- equal-sizedcentra of UNM-LK-I and YPM vertebraof Platecarpus(Cope, 1875,pl. 20, LK-l is a nearlycomplete tooth (fig. 3, A-B) 4672, a specimenreferred to Ectenosaurusby figs. lA-C, pl. 21, figs. lA-B, 2; Williston, that is long, slender,and hasa pointedtip that Russell(1967), reveals that the UNM speci- 1898,pl. 42, figs.3-4). An anteriordorsal is posteromediallyrecurved. This tooth has a men'stransverse processes are approximately vertebraof UNM-LK-l (fig. 3, G-I) is simi- subcircularcross section near the baseof the 30 percentshorter than thoseof YPM 4672. lar, although the centrum is slightly longer crown and bears distinct anterior and pos- Assignmentof UNM-LK-l to Plioplatecarpus and the articular surfacesa little more cir- terior carinaethat run the vertical length of seemsto be precludedby two features: l) cular, being less flattenedtransversely. This the crown. The buccal aspectof this tooth Dollo (1893) stated that Plioplatecarpus has vertebrapreserves the posterior zygopophyses bears six vertical facetswhereas the lingual only l3 dorsal vertebrae,a claim reluctantly acceptedby Russell(1967); UNM-LK-I has l4 dorsalsin its incompletevertebral column,; and 2) accordingto Russell(1967, p. 159)the synapophysesof the anteriordorsal vertebrae of Plioplatecarpusate locatedin the centerof the lateral aspectsof the centra. The syna- pophysesof the anterior dorsals of UNM- LK-l, asnoted above (fig. 3, G-I), arelocated on the anterodorsaledge of the lateralaspects of the centra;this is the samecondition seen in Platecarpus (Russell, 1967). Assignment to Platecarpusis further justified by the fact that UNM-LK-I closely resemblesYPM 1256. 1258,1264, 1269, 1272, and 1286,specimens referredto Platecarpusby Russell(1967). Despite the above characters of UNM- LK-l that seemto precludeits assignmentto Ectenosaurusor Plioplatecarpus, we believe that there is enough uncertaintyabout the diagnosticutility of thesecharacters due to potential variability that we only tentatively assign the specimento Platecarpus. Assign- ment to a speciesof Platecarpusclearly is im- possiblebecause the speciesof the genusare distinguishedby cranial characters(Russell, 1967)not preservedin UNM-LK-1. Platecarpus(fig. 4) is a Campaniangenus of mosasaursknown elsewhere in the WesternIn- terior from the in , , and (Russell, 1967). - Extension of the southward into roughly time-equivalent,though probably slightlyyounger, deposits is not surprisingin view of the great mobility of mosasaursthat gave them an extensivegeographic distribu- tion during the Late Cretaceous(Russell, 1967).

Taphonomy Mosasaur FIGURE 3-SelncreoELEMENrsoF UNM-LK-I, AeARTTALsKELEToNoFcF (A) remains commonly are found PL.arecenpussp.; buccal disarticulated and lingual (B) views of a tower(?) tooth; ventral (C), left lateral (D), and posterior (E) views of an anterior to a degreesimilar to that of caudal vertebra; (F) anterior view ofa thoracic rib; anterior (G), left lateral (H), and posterior (I) views of UNM-LK-I (figs.2, 5, 6); herewe offer some an anterior dorsal vertebra; ventral (J), left lateral (K), and posterior (L) views of a median dorsal observationsand speculationon how this vertebra. Black bars are 3 cm long (one scalefor A and B; one for c, D and E; one for F: and one for G. specimencame to be disarticulatedand then H, I, J, K, and L). buried.UNM-LK-I wasfound in thinly lami-

Augustl98l New Mexico Geology Summaryof marinereptiles in NewMexico Among the Reptilia three main groups adaptedto life in the marine realm: ichthyo- saurs,plesiosaurs, and mosasaurs.Some rep- resentativesof other groups, notably turtles and , have also invaded marineniches, but arenot consideredhere. Ichthyosaurswere a widespreadgroup of fishlike marine reptilesduring the . Although their remainshave been found in and Cretaceousdeposits of (WtlltsroN, ,, FICURE 4-RpcoNsrnucrED sKELEToNor Ptarrc.nnpus rcrERrcus, AcruAL LENGTHABour 6 M America(McGowan, 1978), to 1898). westernNorth our knowledgeno ichthyosaurshave been re- portedyet from New Mexico. nated dark-gray shale suggestiveof an off- first andthe rest of thecarcass fell on top of it, Plesiosaurremains, on the otherhand, have shoreenvironment of relativelydeep and quiet or the jaw broke up and was carriednorth- beenreported from two localitiesin New Mex- water. The anterior and medial dorsal verte- westwardby bottom currentswhere it mixed ico. Cope(1887) described plesiosaur remains bral column was found articulated,though with the vertebraeand sank deeperinto a soft from what he termedthe "Fox Hills bed of slightly twisted in the middle. The posterior bottom than did the vertebrae.The former ex- New Mexico." He assignedthe following tax- dorsal,pygal, and caudalvertebrae are nearly planationis simpler,but the variedaspects of onomic namesto theseremains: Piptomerus all disarticulated;they were probably less the disarticulatedvertebrae exposed on the megaloporus new genus and ,P. tightly bound togetherby bony processes,ax- quarry surface(fig. 6) suggesttumbling and microporus new species,P. hexogonus new ial muscles,tendons, and ligamentsthan the sinking at various anglesinto a soft bottom species, and Orophosaurus pauciporu,snew more anterior parts of the vertebralcolumn. and might support the later explanation.A genusand species. Williston (1903, p. I l) later The degreeof disarticulationof UNM-LK-I third possibilityis that the jaw fragmentsare listed thesetaxa and summarizedtheir sup- suggestsa fairly long periodof decomposition those of a different individual than the poseddiagnostic characters. Welles (1952), in before frnal burial in the sediment. This vertebraeand ribs. We seeno clear way to a revision of North American plesiosaurs, decompositionmay have occurredin part as decide among these three possibilities.Al- consideredall of Cope'staxa to be basedon the dead floated in the water column, though nothing about the size and morphol- indeterminatematerial and thusdeclared them but most decompositionprobably occurred as ogy of the Lewis Shalemosasaur remains to to be nomina vona(vain or void names).The the animal lay on the bottom, sincethe disar- suggestthat they belongedto more than one localityfrom whichthese plesiosaurs were col- ticulatedbones show a preferentialnorthwest- individual, this chasteningpossibility must lectedwas not givenby Copeand the Fox Hills southeastalignment shared by the still ar- alwaysbe entertainedwhen dealing with Formationis not presentin New Mexico, be- ticulated portion of the vertebral column. material in a state of disarticulationor in- ing currently restrictedto strata in North Mixed amongthe disarticulatedvertebrae are completeness. IF invertebrateshell fragments, shark's teeth, andbony fish scalesthat couldrepresent either gut contentsof themosasaur or organicdebris presentin the sedimentwhere the deadanimal cameto rest,or both. verrebroe The orientation of most of the bones (a %% o notableexception is the rib in the lower left Y fl handcorner of fig. 5) suggeststhe presenceof ribrrosmenrs a distinct, though most likely slight, bottom /e)J currentprobably flowing predominatelyto the eog northwestbecause most of the bonesare scat- teredin this direction.The absenceof theskull v and cervicalvertebrae of UNM-LK-l may be o becausethe anterior end of the animal first /1 was exposedin an arroyo (fig. 5); these elements,if they were fossilized,have long since eroded away. The girdles and appen- dages, on the other hand, may have been removedin a numberof ways. A number of grooves and scratcheson vertebraeand rib fragmentsof UNM-LK-I may indicatescavenging, a plausiblemecha- nismby whichthe girdles and appendages may havebeen removed. However, the specimenis -t so damagedby weatheringand the rootsof re- l/4m cent plant growth that we hesitateto support Mososour sucha conclusionfirmly. The girdlesand ap- quorry pendagessimply may havefloated away once mop they becamedetached from the vertebralcol- umn or may have fallen off elsewherewhen I the decomposinganimal was floating in the A eroded watercolumn. jaw Most difficult to explain is how the FIGURE 5-Mep oF rHE DrsrRrBUTroNoF BoNEsoN rHE euARRy FAcEAT UNM-V-070. The jaw and tooth fragments came to be buried beneath the fragments were found beneath the disarticulated vertebrae in the center of the drawing (fig. 6). Erosion of mixed-upposterior dorsal, pygal, and caudal an arroyo first exposedthe southern end of the articulated vertebral column and may have removed the vertebrae.Either the iaw of the animal fell and .

New Mexico Geology Augustl98l Cope's specimenof Z. dyspelor was Cross, W., Spencer, A. C., and Purington, C. W., collectedby W. B. Lyon, a surgeonstationed 1899, Description of the La Plata quadrangle: at Fort McRae,an old army post that wasjust U.S. Geological Survey, Geol. Atlas, Folio 60, east of the presentsite of Elephant Butte l4 p. Reservoirin south-centralNew Mexico(Cope, Cunningham, J.8., 1966, A Cretaceousvertebrate from the Big Burro Mountains, Grant County, l87lb). In his final description of this New Mexico (abs.): New Mexico Geological Soci- specimen,Cope (1875, p. 167)explained that ety, Guidebook lTth field conference,p. I 19 it came"from the yellowbeds of the Niobrara Dane, C. H., 1936, The La Ventana-Chacra Mesa epochof the Jornadadel Muerto, near Fort coal field, pt. 3-of geology and fuel resourcesof McRae,New Mexico." Copeprobably was re- the southern part of the San Juan Basin, New ferring to bedsof the MancosShale that are Mexico: U.S. Geological Survey, Bull., v. 860-C, exposedin the Jornada del Muerto region p.8l-l6l (Kelleyand Silver, 1952)and are, in part, a Dollo, L., 1893, Nouvelle note sur I'osteologie des FIGURE 6-Donsel, pycAI-, AND cAUDAL vERrE- mosasauriens:Soci6t6 Belge de G6ologie, Bull., v. BRAELYING MIXED UP AND DISARTICULATED ON THE correlativeof the NiobraraFormation. p.219-259 (1917, 6, euARRy FACEAT UNM-V-070. These vertebrae Lee p. 46-47)canbe credited with the Fassett, J. E., and Hinds, J. S., 1971, Geology and are some of thosejust north of the articulated por- other two previousreports of mosasaursfrom fuel resources of the and tion of vertebral column in fie. 5. New Mexico. He listed Mososaurussp. (sic) Kirtland Shale of the San Juan Basin, New Mex- from two localitiesin the Raton Mesaregion: ico and : U.S. Geological Survey, Prof. l) wall Canyon,about 4 Paper 676,76p. Dakota, South Dakota, , Wyoming, "North of Cimarron mi northwest 100ft belowtop of Kelley, V. C., and Silver, C., 1952, Geology of the and Colorado as far south as the Colorado of Cimarron; Pierre Shale and 2) Bremmer Canyon, Caballo Mountains: University of New Mexico, Springsarea (Waage, 1968). Despite this, two "Van New Mexico, a mile from its mouth, in slide Pubs. in Geology, v. 4, 286 p. cluesto the provenanceof Cope'splesiosaurs W. Raton rock: at base of ."Un- Lee, T., l9l'7, Geology of the Mesa and are available:l) the specimenlabel with the other regions in Colorado and New Mexico: U.S. fortunately,Lee did not describeor illustrate type of Orophosaurus pauciporus, AMNH Geological Survey, Prof. Paper l0l , p.9-221 any specimensso their assignmentro Mosa- 5692,states the locality as "Cretaceous.San Leidy, J., 1873, Description of remains of reptiles saurusr unverified. Juan Basin,N.M." and 2) the term Fox Hills emains and from the Cretaceous formations of the greatly in- bed usedby Cope(1887) would havereferred AcxNowI-pncMENTS-Weare interior of the : U.S. Geological debted the Jicarilla Survey of the Territories (Hayden), Rept., v. I p. to the uppermostmarine Cretaceous below the to numerousmembers of , Apache Indian Tribe for aid, interest, 266-3tO continentalcoal-bearing strata of what was their and enthusiasmwhich enabledthe collection Mannhard, G. W., 1976, , sedimentol- then called the "," even of the specimendescribed here. We specifi- ogy, and paleoenvironments of the La Ventana outsidethe areaswhere these formations are (CliffHouse cally thank LeonardAtole, Tribal President, Tongue Sandstone)and adjacent for- now consideredto be present(K. Waage,per- mations of the (Upper Creta- under whoseauspices the work was done;Joe sonal communication, 1980). The Laramie ceous), southeasternSan Juan Basin, New Mex- Muniz, Director Tourism,who enthusiasti- Formation in the San Juan Basin in Cope's of ico: Ph.D. thesis, University of New Mexico, 182 cally pursuedthe investigationand authorized day encompassedrocks now referred to the p. Fruitland and Kirtland Formations(Reeside, an extendedIoan of the specimento the McGowan, C., 1978, Further evidence for the wide New Adolph Julian geographical distribution of taxa 1924).Cope's Fox Hills bed,which produced Universityof Mexico;and first found (Reptilia: Ichthyosauria): Journal of Paleon- theplesiosaurs, must bewhat is now calledthe and Darrell Paiz whosesharp eyes the specimen.Barry Kues, Niall Mateer, and tology, v. 52,p. 1,155-1,162 PicturedCliffs Sandstoneor Lewis Shale,or O'Sullivan, R. B., Repenning, C. A., Beaumont, E. perhapsincluded parts of both. Cope's in- Robert Sullivanreviewed an earlier draft of this paper;their commentshave improved its C., and Page, H. G., 19'12,Stratigraphy of the defatigable collector David Baldwin, who Cretaceous rocks and the Tertiary Ojo Alamo Barry Kueswas especially worked in the San Juan Basin during the contentand clarity. Sandstone, Navajo and Hopi Indian Reserva- in pointing referencesto 1880's,most certainly found these specimens. helpful out obscure tions, Arizona, New Mexico, and Utah: U.S. New Mexico's Cunningham(1966) publishedthe second marinereptiles. Geological Survey, Prof. Paper 521-8, 65 p. report of plesiosaurremains from New Mex- Reeside,J. B., Jr. , 1924, Upper Cretaceousand Ter- part ico by mentioningeight vertebraeof a tiary formations of the western of the San "Cre- References Juan Basin of Colorado and New Mexico: U.S. taceousvertebrate" from the ColoradoShale Geological Survey, Prof. Paper 134, 70 p. Cobban, W. A., Landis, E. R., and Dane, C. H., in the Big Burro Mountainsof southwestern Russell, D. A., 1967, Systematicsand morphology 1974, Age relations of upper part of Lewis Shale New Mexico. Subsequently,J. T. Gregoryof of American mosasaurs: Yale Peabody Museum on east side of San Juan Basin, New Mexico: New the Universityof (Berkeley)iden- of Natural History, Bull., v. 23,240 p. Mexico Geological Society, Guidebook 25th field Waage, K. M., 1968,The type , tified theseas belongingto an elasmosaurid conference,p.279-282 Cretaceous (Maestrichtian), South Dakota, pt. plesiosaur(J. Cunningham,personal commu- Cope, E. D., l87la, (Verbalcommunication on rep- I -stratigraphy and paleoenvironments: Yale nication,1980). tilian fossils from , New Mexico, and Peabody Museum of Natural History, Bull., v. The first previous report of a mosasaur Kansas): American Philosophical Society, Proc., 27,175p. from New Mexico v. l l, p. 57l-572 mentionedat the beginning Welles, S. P.,1952, A review of the North American l87lb, On some speciesof of this paperwas Cope's (l87la, p. 572)brief Cretaceouselasmosaurs: University of California, from the Cretaceous beds of Kansas and New descriptionofa seriesofvertebrae from "near Pubs. in Geology, v. 29, p. 47-144 Mexico: American Philosophical Society, Proc., Fort McRae. New Mexico" to which he at- Williston, S. W., 1898, Mosasaurs: University v. ll, p. 5'74-584 tached the Geological Survey of Kansas,v. 4, p.83-221 name Liodon dyspelor n. sp. 1871c,On the fossil reptilesand fishesof the 1903, North American plesiosaurs, pt. l: Cope (l87lb, c) later describedthis specimen Cretaceous rocks of Kansas: U.S. Geological Field Columbian Museum Geological Series,v. 2, in greaterdetail, Iisting measurementsof the Survey of Wyoming (Hayden), Fourth Annual no.l, 77p. vertebraeas well. Specimensfrom the Kansas Rept., p. 385-424 Cretaceous referred to Z. dyspelor were 1872, Catalogue of the Pythonomorpha describedand comparedto the New Mexico found in the Cretaceous strata of Kansas: specimenby Cope (1872),but it was Leidy American Philosophical Society, Proc., v. 12, p. (1873,pls. 35-36) who first illustrated the New 264-287 Mexicospecimen. Leidy (1873, p.271-274) re- 1875,The vertebrata of the Cretaceousfor- ferredZ. mations of the West: U.S. Geological Survey of dyspelorto Tylosaurus;according to the Territories (Hayden), Rept., v. 2, 302 p. Russell(1967, p. 184),T. dyspeloris basedon 1887, The sea-saurians of the Fox Hills indeterminatematerial and thusis bestconsid- Cretaceous: American Naturalist, v. 21, p. 563- ered,a nomenvanum. 566

Augustl98l New Mexico Geology