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New Mexico Gcological Society Guidebook, 54th f ield Conference, of the Zuni Plateau, 2003, p. 241 -244.

TETRAPOD FOOTPRINTS FROM THE MIDDLE (PEROVKAN­ EARLY ) MOENKOPI FORMATION, WEST-CENTRAL

SPENCER G. LUCAS, ANDREW B. HECKERT AND ADRIAN P. HUNT New Mexico Museum of Natural History, 180 I Mountain Rd N\V, Albuquerque, NM 87104

ARSTR,\CT.-Tetrapod footprints from a locality ncar Prewitt, Cibola County, New Mexico, are in the lowcr part of the Amon Chico Mcmber of the Moenkopi Formation. These Perm'kan age (early Anisian) footprints represent three tetrapod ichnotaxa: swimming traces, Citi/Vlhc/"illlll and Therapsiplis. These New Mexican Moenkopi trtlcks are part of a Euaramerican Chirolherilllll ichnofauna of Early- age. They also rcamnn that the tetrapod ichnofauna of the Mocnkopi f om1ation, which is archosaur and dieynodol1t dominated, is sampling a dif­ ferent vertebrate fauna than the temnospondyl-dominated body fossil assemblages of the unit.

INTRODUCTION Chinle Gp. (Zuni Mts. Fm.) 10 (), Tetrapod footprints have long bccn known from the Tri assic 9 Mocnkopi Formation in , and Peabody (1948) described 8 them in a now classic monograph. In 1988, one of liS (SGL) dis­ c 7 covered tetrapod footprints in the Mocnkopi Formation of west­ .Q ~ -.0 6 central Ncw Mexico. Lucas and Hayden (1989, p. 194, fig. 4d) ~~ 5 mentioned this OCCUlTence, illustrated "reptile swinuning traces," o~ ()0 scale 1= 2 m and noted that the ichnofauna is dominated by a " large-manus LL:c ChimtheriulII." Hunt and Lucas ( 1993) briefly described and ·o.U illustrated some tracks from the locality, attributing them to a new o c -'"'c.8 4 ichnotaxon similar to Therapsiplis (named elsewhere in th e samc OJ c volume by Hunt et aI. , 1993) and to swimming traces. In this 0« ~~ paper, wc provide detailed documentation of the Moenkopi tetra~ N MM NH pod footprints from west-central New Mexico. NMMNH refers 3=*?;:::::::;:=~o::::J to the New Mexico Muscum of Natural Hi story, Albuquerque. ~San:::~2i~~~~·~ Andres locality 356 LOCALITY Formation

The Moenkopi track locality is NMMNH locality 356, in the c=::J , limy NE 1/4 NW 114 SE1I4, sec. 36, Tl 3N, RI2W, Cibola County, about 6 km south of Prewitt (Fig. I). Stratigraphically, the track-beari ng c:=:=J sandstone bed is a ripple-laminated to massive, fin e-grained sandstone in the [J,7iJli] pedoturbation lowcr 0.5 m of the Anton Chico Member of the Moenkopi Fonna­ j siltstone tion. The principal track-bcaring layer preserves 1110st tetrapod r -- tracks in convex epirelief together wi th no ndescript invertebrate 1\ · ,I sandstone, cross bedded fceding traces and abundant desiccation cracks. The Anton Chico Member is of Perovkan (early Anisian) age, and a correlative of ~ the Holbrook Member of the Moenkopi Formation in Arizona (Morales, 1987; Lucas, 1998; Lucas and Schoch, 2002). ~ conglomerate

ICHNOTAXA FIGURE I. Index map and stratigraphic section showing the distribluion of Triassic strata in New Mexico and the location ofNMMNH locality The NMMNH collection includes 13 ca talogued specimens 356 (star 011 inset map). of Moenkopi tracks from NMMNH locality 356. Three discrete tetrapod ichnotaxa are present: tetrapod swimming traces, Chi­ J"Olheriul11 and Therapsip1l5 (Figs. 2-3). by Lucas and Hayden (1989, fig . 4) and by Hunt and Lucas (1993, fi g. 23c-d). NMMN H spccimens 14 147, 14148, 14150, Swimming Traces 141 55 and 141 57 (Fig. 3A) are characteristic. Other swim traces were not collected. The NMMNH specimens consist of straight Tetrapod swimming traces arc thc 1110st abundant tetrapod grooves (parallel scratch marks) up to 100 nml long and 15 nml ichnofossi ls at NMMNH locality 356, and have been illustrated wi de. Therc arc as many as five parallel grooves on some traces. 242 L UCAS, HECKERT AND H UNT

NMMNH P-26037 (Fi gs. 2A, 3C) is a tridactyl print that is 65 111m wide and 72 mm long. We identify it as a partia l manus imprint preserving digits 2, 3 and 4, which are subequal in length. These specimens show diagnostic features of Chirotilerillm, to which they are assigned (cf. Peabody, 1948; Haubold, 1971 , 1984). With a pes length of almost II cm, th e Ch irotherilllll A specimens from NMMNH locality 356 are medium sized, about 120 mm the size of C. lIIinlls, C. barthi or C. coltolli (Peabody, 1948). However, given their poor prese rvation and the oversplit ichno­ species-level taxonomy of Ch irof/zeriulI1, we onl y identi fy the locality 356 specimens as Chirof/JerilllJl sp.

Thel'apsiplIs

Several specimens (NM MNH P-14153, 14 154, 14 156 and 14161 ) from locality 356 are assignable to TherapsipIIs, a tet­ rapod ichnogenus described by Hunt et al. (1993) from the Hol­ brook Member of the Moe nkopi Formation in eastern Arizona . These specimens (e.g., Figs. 2C, 3D) have pes prints that are 120- B 140 mm wide, 130-l50 1lU11iong and have fi ve digits, each about 50 nUll long. They are the tracks of a quadmped with a pentadac­ tyl manus and pes of nearly equal size, with a low pace angulation and without a di ve rgent digit 5. The digit tips are acute. NM MNH P-14153 (F ig. 3E) is a trackway of about 10 prints, and indicates a trackway width of about 380 mm , a feawre that also di stingui she s them from the much narrower track ways of Cizirolherilllll. These tracks most closely resemble Tizerapsiplls, to which they are assigned (Hunt et aI. , 1993). Howeve r, given their poor preservation, we on ly assign them to Tizerapsipus sp.

DISCUSSION

c The presence of tetrapod tracks in the Anton Chico Member of the Moenkopi Formation is not surpri si ng and further supports FIGURE 2. Outline drawings of selected tetrapod footp rints from correlation of the Anton Chico Member to the Holbrook Member NMMN H loca lity 356. A. NMMNH P-26037, incomplete manus? in Arizona, which also yields Chirotheriul1I tracks. Indeed, there impression ofChirorherill1ll sp. 8. NMMN H P-14 14 6, ri ght pes impres­ appears to be a global tetrapod iclmoassemblage charac teri zed sion of ChirorheriulII sp. C. NMMN H P-14161 , right pes impression of by tracks of Chirotheril/III in red beds of late Early (O lenekian Therapsipus sp. = Nonesian) and early Middle (Anisian = Perovkan) Triassic age. Key loca lities are: I. Gennan Buntsand stein , where most Chiro llz eriulIl track­ Similar traces from the Moenkopi Formation in Wyoming and sites are of Nones ian age, but some are of Perovkan age (e.g. , have been interpreted as tetrapod sw il11l11jng traces, and we Haubold, 1971, 1984; Haderer et aI. , 1995). follow thi s interpretation (Boyd and Loope, 1984). Clearly, they 2. Buntsandstein of France , correlative to the Buntsa ndstein indicate subaqueous conditions at the time the traces were made. records in Germany. 3. Middle Triassic of the Italian Dolomites (Avanzini et aI., Chil'otlreriuJII 2001 ). 4. Ea rly and Middle Triassic Moenkopi Formation, Arizona Two co ll ected specimens appear to belong to the characteristic and Utah (Peabody, 1948). Earl y-Middle Triassic tetrapod ichnogenus Chirotheriu1ll. These 5. The New Mexican Moenkopi reco rd documented here. are the tracks of pentadactyl quadmpeds with clawed digits in The ClzirotheriwlI ichnofauna can thu s be considered a Eura­ whi ch the pes is much larger than the manus. NMMNH P-14146 merican ichnofauna of Nonesian-Perovkan age. (Figs. 28 , 38) is a fi ve-toed track that is 98 mm wide and 106 nm1 The tetrapod ichnofauna previously reported from the Moen­ long. We identify it as a right pes impression with digit 5 well di s­ kopi Fonnation is dominated by tracks of archosa urs (Chiro rh ­ placed postero-Iaterally from the row of di gits 1-4. Digit 3 is lon­ ail/III) and of therapsids (TherapsipIIs) (Peabody, 1948; Hunt et gest and slightl y lon ge r than di git 4, which is longer than digit 2. aI. , 1993). The locality reported here is consistent with this conclu- TETRAPOD FOOTPRINTS FRO;-"'I THE MroDlE T RIASSIC MOENKOPI F ORMATION, NEW M EXICO 243

FIGURE 3. Selected tetrapod footprints from l\TMMNH locality 356. A. NMMNH P-14157, reptile swimming traces. B. NMMNH P- 14146, right pes impression of Chirotherilllll sr. C. NMMNH P-2603 7, incomplete manus? impression of Chirorherilllll sp. D. NMMNH P- 14161 , right manus and pes impressions of Therapsiplls sp. E. NMMNH P-14l53. left pes impression of ThempsiplIs sp. Scale bars on the photographs are in cm.

sion. However, the body fossi l Lluna of the Moenkopi Fonnation is M., 200 I, Pennian and Triassic tetrapod ichnofaunal units of northern Italy: tenmospondyl dominated, with much less common archosaurs and Their potential contribution to continental biochronology: Natura IJrcsciana, no. 25 , p. 89-107. no documented therapsids (Morales, 1987; Boy et aI., 200 I; Lucas Boy, J. A.. Schoch, R. R. and Lucas. S. G .. 2001. The Moenkopi Fonnation in and Schoch, 2002). This indicates that different palls of the verte­ cast-centra l Ncw Mexico: Stratigraphy and vcrtebra! e fauna: New iv1cxieo brate fauna during Moenkopi time arc being sa mpled by the body Geological Society, Guidebook 52, p. 103-109. fossil and ichnofossil records. It also suggests that Boyd, D. W. and Loope. D. 8., 1984, Probable vertebrate origin for cel1ain sale marks in Triassic red beds in Wyoming: Joumai of Paleontology, v. 58, p. body fossils should be discovered in the Moenkopi Fonnation. 467-476. Haderer, F., Demathieu, G. R. and Bottcher, R.. 1995. Wirbeltier-Fiihrten aus ACKNOWLEDGMENTS clem ROlqllarzil (Oberer lJuntsanclstcin, Mittlere Trias) von Hardheim bci WenheimJ1..,lain (Stiddei tschland): Stuttganer Hcitragc zur Na turl..'Unde Serie 8. no. 230, 31 p. Pete Reser and several NMNINH vo lunteers assisted in the Iiallbold, H.• 1971, lchnia Amphibiorum CI RCplilionnll fossilium: Handbook of field. Martin Lockley and Kate Zeigler provided help fu l reviews Paleoherpetology, v. 18, 124 p. of the manuscript. Haubold, H .. 1984, Saurierflilu1en. Wi ttenberg Lutherstadt, A. Ziemsen Verlag. 231 p. Hunt. A. P. and Lucas, S. G. , 1993, Tetrapod footprints from th e Middle Triassic REFERENCES Moenkopi Formation. west-central New Mexico: New Mexico Museum of Natliral HislO!Y and Science, [Jnllclin J, p. G20 Avanzini, M., Ceoloni, P.. Conti, ivl. A .. l eonardi, G. , Manni, R. . ivlariotti. N., Hunt. A. P. . Santucci, V. l ., Lockley. 1'..,1. G. and Olson. T. J. , 1993. Dicynodolll Mietto, P., Muraro. C, Nicosia. U .. Sacchi, E .. Santi. G. and Spezzamome, trackways from the Holbrook Member of the Moenkopi Formation (Middle 244 L UCAS, H ECKERT AND H UNT

Triassic: Anisian), Arizona, USA: New Mexico Museum of Natural History American Moenkopi Fonnation: Lethaia. v. 35. p. 97-106. and Science Bulletin 3, p. 213-218. Morales. M .. 1987. Terrestrial fauna and flora from the Triassic Moenkopi For­ Lucas, S. G., 1998. Global Triassic tetrapod biostratigraphy and biochronology: mation of the southwcstem : Jouma[ of the Arizona· PlIlacogcography. Palaeoclimatology, Pataeogeogmphy. v. 143. p. 3·l7·384. Academy of Science. v. 22, p. [·20. Lucas, S.G. and Hayden, S.N .. 1989, Triassic slratigmphy of west-central New Peabody, F. E., [948. Reptile and trackways from the Lower Triassic Mexico: New Mexico Geological Society. Guidebook 40. p. 19 1-211. Moenkopi Formation o f Arizona and Utah: Unh'ersiry of Cali fomi a Publica·

Lucas, S. G. and Schoch, R. R. t 2002, Triassic tenmospondyi biostratigraphy, tions. Bulletin of the Department of Geological Sciences, v. 27, p. 295-420. biochronology and correlation of the Gennan BUlltsandstein and North