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Dinosaurs of New Mexico Lucas, S.G., and Heckert, A.B., eds., 2000, Dinosaurs of New Mexico. New Mexico Museum of Natural History and Science Bulletin No. 17. 1 DINOSAURS OF NEW MEXICO: AN OVERVIEW SPENCER G. LUCASl and ANDREW B. HECKERT2 lNew Mexico Museum of Natural History, 1801 Mountain Road NW, Albuquerque, NM 87104; 'Department of Earth & Planetary Sciences, University of New Mexico, Albuquerque, NM 87131 Abstract-New Mexico is in the forefront of dinosaur-collecting grounds. AnalysiS of the state's dino­ saur fossils has been far reaching, touching upon every aspect of dinosaur paleontology, including biogeography, biostratigraphy, functional morphology, paleoecology, phylogeny, taphonomy and tax­ onomy. This volume brings together studies of New Mexico's dinosaurs in all of these areas of re­ search, as well as up-to-date reviews of New Mexico's dinosaur fossil record and the scientific litera­ ture based on it. INTRODUCTION tum overlain by the Whitaker quarry and its hundreds of pre­ served Coelophysis skeletons. New Mexico's record of Late Trias­ Cope (1885) published the first scientific report of dinosaur sic dinosaurs has thus emerged as one of the most extensive fossils from New Mexico. In the 115 years that followed, discov­ known, and is significant for several reasons: eries in Triassic, Jurassic and Cretaceous rocks have placed New Mexico in the forefront of dinosaur-collecting grounds (Fig. 1). • Some of the Upper Triassic dinosaur fossils from New Analysis of New Mexico's dinosaur fossils has been far reaching, Mexico are among the oldest known dinosaurs and touching upon every aspect of dinosaur paleontology, including thus are critical to analysis of dinosaur origins. biogeography, biostratigraphy, functional morphology, paleoecol­ • Two holotype taxa of Triassic ornHhischians and as ogy, phylogeny, taphonomy and taxonomy. Indeed, this volume many as six species overall come from New Mexico brings together studies of New Mexico's dinosaurs in all of these and are a significant component of a very scanty areas of research, as well as up-to-date reviews of New Mexico's record of Triassic ornithischians worldwide. dinosaur fossil record and the scientific literature based on it. To put these articles into broader perspective, we present an over­ • The youngest herrerasaurid dinosaurs are from New view of scientific research on New Mexico's dinosaurs. Mexico. • Recent discovery of the Snyder quarry near Ghost TRIASSIC DINOSAURS Ranch, and recognition of Eucoelophysis (Sullivan and In 1887, Cope proposed the first scientific name for a New Lucas, 1999), establishes a stratigraphic (temporal) Mexican dinosaur, the Triassic theropod now called Coelophysis succession of Late Triassic theropods in the Chama bauri, New Mexico's State Fossil by act of the State Legislature. In basin, the only such succession known. 1947, George Whitaker's phenomenal discovery of the Upper Tri­ Furthermore, New Mexico has a substantial record of Late assic dinosaur quarry at Ghost Ranch revealed a bonebed of hun­ Triassic dinosaur footprints, including both theropod and dreds (thousands?) of theropod skeletons, the singlemost exten­ prosauropod tracks (see Hunt et aI. and Lockley et aI., this vol­ sive fossil assemblage of Triassic theropods known, and probably ume). We anticipate that ongoing collecting efforts will uncover the largest, by number, accumulation of theropods in the fossil many new and significant dinosaur records from New Mexico's record. Upper Triassic strata that will continue to improve our nascent Colbert (1989) mono graphed these the·ropods, yet much understanding of dinosaur origins and early evolution. more research remains to be undertaken on them. Especially needed is a thorough study of their osteological variation to iden­ JURASSIC DINOSAURS tify features that are of ontogenetic, sexual dimorphic or alpha­ taxonomic significance. Because of this, no consensus has been Lucas and Hunt (1985) published the first comprehensive reached on how many taxa are in the Ghost Ranch quarry (see review of New Mexico's Jurassic dinosaurs, bringing together a Downs, this volume). welter of disparate reports, mostly of isolated bones and teeth Until about the time of Colbert's (1989) monograph, virtu­ from the Brushy Basin Member of the Morrison Formation. Most ally nothing was known of New Mexico's Triassic dinosaurs out­ puzzling to them was the absence of a major Morrison dinosaur side of Ghost Ranch. In that year, Hunt (1989) described a new quarry in New Mexico, unlike many other western states (Okla­ ornithischian dinosaur from isolated teeth found in slightly older homa, Colorado, Utah, Wyoming) in which one or more mass j. strata near Tucumcari, Revueltosaurus callenderi. Since then, nu­ death assemblages have been found in the Morrison Formation. merous Triassic dinosaur fossils-mostly isolated bones and teeth, However, the Peterson quarry near Laguna (see Heckert et al., but also partial skeletons-have come from New Mexico (see this volume) is a major dinosaur bonebed in the New Mexican Heckert et aI., this volume). Importantly, this record is Morrison Formation. First discovered in the 1960s, its significance stratigraphically superposed and thus particularly significant has only been appreciated during the last few years through the when studying Triassic dinosaur evolution. For example, the old­ yeoman collecting efforts of dedicated New Mexico Museum of est and most fragmentary Triassic dinosaurs from New Mexico Natural History volunteers directed by Ron and Rod Peterson are among the oldest known anywhere. Overlying these are more and Dan D'Andrea. The Peterson quarry is a fluvially-concen­ diverse and better preserved dinosaur faunas, including the type trated bonebed, mostly of diplodocid sauropods, but including a of Eucoelophysis baldwini Sullivan and Lucas and the Snyder quarry, very large theropod, in the Brushy Basin Member, as are most of which yielded the oldest known coelophysoid skull. These are in the great Morrison dinosaur quarries. • 2 dinosaurs Paleocene dinOSaurs?1 Ma age principal rock units I 65 Tyrannosaurus rex, Lancian Tyrannosaurus tracks, Alamosaurus (J) Edmontonian ::J Fruitland-upper Parasaurolophus, Q) Kirtland formations 0 ....... Pentaceratops UJ CO () .....J ~ UJ a: Mussentuchitian >. Dakota Group Iornithopod tracks () -;:::: Cashenranchian CO UJ Buffal 145 Peterson quarry, Diplodocus, Allosaurus, CD Morrison +-' Stegosaurus, ro Formation U --' Camarasaurus, etc. (/)- oldest New Mexican sauropods, (/) CD Summerville Formation theropod tracks « ""0 ~ ""0 ~ ......,=> 200 Apachean Coelophysis I U (/) Revueltian ornithischians, theropods (/) CD Chinle « +-'ro Group - --' Adamanian I oldest New Mexican dinosaurs I r-~ Otischalkian 225 FIGURE 1. Swrunary of New Mexico's dinosaur record. Most other New Mexican Jurassic dinosaur occurrences are shown to lack a sound scientific basis (see Lucas, this volume). singleton specimens, mostly of sauropods. Perhaps the most no­ Thus, outside of the Peterson quarry, New Mexico's record torious of New Mexico's Jurassic dinosaurs was "Seismosaurus," of Jurassic dinosaurs remains sparse. The are no Lower Jurassic the subject of several articles and a book (e.g., Gillette, 1991, 1994). rocks in New Mexico, and the Middle Jurassic rocks are mostly However, the claims of generic distinctiveness, colossal size and eolian and therefore unlikely to preserve dinosaur bones, though extensive gastroliths of "Seismosaurus" have been re-evaluated and they may contain an undiscovered dinosaur track record. Never- 3 theless, a couple of significant points can be derived from New • Asian elements in the San Juan Basin Campanian fau­ Mexico's Jurassic dinosaur fossils: nas (Nodocephalosaurus, Saurornitholestes, Prenocephale) indicate biogeographic interchange between North • A sauropod record in the Summerville Formation in America and Asia, but center(s) of origin and direc­ north-central New Mexico is among the oldest North tionality of inunigration remain unclear. American sauropods (d. Gillette, 1996). • A consensus on the ages of the dinosaur dinosaur • Generically identifiable Morrison Formation dino­ fossils close to the Cretaceous-Tertiary boundary in saurs from New Mexico are Camarasaurus, Diplodocus, the San Juan Basin has still not been achieved. The and taxa charac­ Apatosaurus, Allosaurus, Stegosaurus, pOSSibility of Paleocene dinosaur fossils here remains teristic of the Morrison Formation dinosaur fauna (Fassett et aI., 2000; Fassett and Lucas, this volume). throughout the Western Interior. This indicates no provincialization or uniqueness of the dinosaurs in During the 1980s and 1990s, Cretaceous dinosaur fossils the New Mexican portion of the Morrison basin (see began to be discovered outside of the San Juan Basin, especially Foster, this volume). in the Moreno Hill Formation in west-central New Mexico (Wolfe and Kirkland, 1998; Wolfe, this volume), in the McRae Formation Further work with pick and shovel is needed to develop a in south-central New Mexico (Lozinsky et al., 1984) and in the more significant record of Jurassic dinosaurs in New Mexico. Ringbone Formation in southwestern New Mexico (Lucas et al., 1990). Particularly interesting records from these units include: CRETACEOUS DINOSAURS (1) Zuniceratops from the Moreno Hill Formation, the oldest North American ceratopsian with brow horns, raising the possibility of Cope's (1885) first report of dinosaur fossils from New a North American origin of ceratopsids (Wolfe and Kirkland, 1998); Mexico was of teeth
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