Robert M. Sullivan

Late Triassic dinosaursfrom the western United States

Western North America has one of the most extensive fossil records of Late Triassic dinosaurs. AllUpper Triassic strata are assigned to the Chinle Group which yields four successive, dinosaur-bearing faunas. Otischalkian (early Tuvalian) dinosaur specimens are fragmentary and indeterminate. Adamanian (late Tuvalian) dinosaurs include a herrerasaurid, Camposaurus arizonensis nov. gen. et sp., Caseosaurus crosbyensis nov. gen. et sp., Tecovasaurus murryi, a new ornithischian and an indeterminate prosauropod. Revueltian (early-middle Norian) dinosaurs include Chindesaurus bryansmalli, two new herrerasaurids, a prosauropod, Revueltosaurus callenderi, Technosaurus smalli, Lucianosaurus wildi, Protoavis texensis and the original syntypes of Coelophysis bauri. Apachean (Rhaetian) evidence for dinosaurs is principally ichnological (Grallator, Pseudotetrasauropus, Tetrasauropus), but at least three dinosaurs are known from osseous remains, including the neotype of Coelophysis bauri. Dinosaurs define three biogeographic provinces in the Late Triassic. In North America, dinosaurs are rare before the late Tuvalian (late Carnian) and appear to become increasingly numerous through the remainder of the Late Triassic.

Revision of the dinosaur Stegoceras Lambe (Ornithischia, Pachycephalosauridae)

Abstract Stegoceras (sensu lato) has been the recipient of a number of species. Most have been placed into synonymy with S. validum, some have been transferred to other genera (i.e., Gravitholus, Ornatotholus), whereas others have been interpreted as being sexual dimorphs. A parsimonious phylogenetic analysis using 49 characters, which include 9 new cranial characters based on pachycephalosaur frontoparietal domes, now permits a revision of the genus Stegoceras. This analysis concludes that Stegoceras validum (sensu stricto) is a primitive, incipiently-domed pachycephalosaur that is characterized by a well-developed squamosal shelf and open supratemporal fossae. It is the sister taxon to the fully-domed Pachycephalosaurinae. The taxon Ornatotholus browni has a parietal and displays features identical to S. validum and is therefore a subjective junior synonym. Specimens consisting of flat, paired frontals are immature individuals of S. validum. The holotype of “Stegoceras” lambei, and all morphotypes of this species, are unique in the construction of the posterior squamosal region and are placed in a new genus, Colepiocephale. Colepiocephale lambei is known solely from the Foremost Formation and is the oldest diagnostic pachycephalosaur from North America. An incomplete, and indeterminate, skull from the upper part of the Milk River Formation (upper Santonian) has the distinction of being the oldest known North American pachycephalosaur. “S.” sternbergi lacks a posterior squamosal shelf and has squamosals directed laterally and is placed in a new genus, Hanssuesia, as H. sternbergi. Although the taxon Gravitholus albertae displays some characters (i.e., retention of the posterior squamosals separated by a distinct median parietal) and is similar to H. sternbergi in some respects, the holotype is too incomplete for any definitive diagnosis and thus it is considered a nomen dubium. Sphaerotholus is a subjective junior of Prenocephale and the species Sphaerotholus buchholtzae is a subjective junior synonym of Prenocephale edmontonensis. The taxa Prenocephale brevis, P. edmontonensis, and P. goodwini, form a monophyletic clade with monotypic Asian taxa Prenocephale prenes and Tylocephale gilmorei as an unresolved sister group. They are united by the possession of a distinct row of nodes on the squamosal and parietals. Tylocephale, if valid, is interpreted as the sister taxon to the Prenocephale clade. Stenotholus kohleri is formally recognized as a junior synonym of Stygimoloch spinifer. Based on the presence of hypertrophied nodes Stygimoloch spinifier and Pachycephalosaurus wyomingensis are united in the clade Pachycephalosaurini new taxon. Small-to-medium size Late Cretaceous pachycephalosaurs were rather diverse, especially during the late Campanian (Judithian), and many species coexisted during Campanian and Maastrictian times. Ancestry and directionality of dispersal (in part) of the North American and Asian taxa remains uncertain and certainly antedates Campanian time.

Eucoelophysis baldwini a new theropod dinosaur from the Upper Triassic of New Mexico, and the status of the original types of Coelophysis

ABSTRACT Eucoelophysis baldwini is a new genus and species of theropod dinosaur from the Upper Triassic Petrified Forest Formation of the Chinle Group in north-central New Mexico. Eucoelophysis baldwini is diagnosed by the autapomorphous structure of its pubis (presence of ischio-acetabular groove), and femur, which has a sulcus in its proximal surface. It differs from Coelophysis bauri and Syntarus rhodesiensis in lacking a well-developed posterior femoral notch below the femoral head. It is further distinquished from Coelophysis bauri in having a tibia that has a distinct appressed surface along the distal two-thirds of the bone and lacks a fibular crest. The original syntypes of Coelophysis longicollis (Cope, 1887a) include a pubis with autapomorphies of Eucoelophysis baldwini and can be assigned to that taxon. Many of the other syntypes of C. longicollis, C. bauri and C. willistoni probably also belong to E. baldwini, but this cannot be demonstrated with certainty. The type horizon of E. baldwini is i...

Nodocephalosaurus kirtlandensis, gen. et sp. nov., a new ankylosaurid dinosaur (Ornithischia: Ankylosauria) from the Upper Cretaceous Kirtland Formation (upper Campanian), San Juan Basin, New Mexico

ABSTRACT A partial skull of a new ankylosaurid dinosaur, Nodocephalosaurus kirtlandensis gen. et sp. nov., differs from known ankylosaurids in possessing a distinctive post-maxillary/lacrimal (osteoderm) ridge and a prominent quadratojugal protuberance that projects anteroventrally. Furthermore, it is distinguished by semi-inflated to bulbous, polygonal, cranial osteoderms that are bilaterally and symmetrically arranged on the frontonasal region of the skull, similar to the Asian ankylosaurids Saichania chulsanensis and Tarchia gigantea. Nodocephalosaurus kirtlandensis and these Asian genera are thus interpreted as composing a clade within the Ankylosauridae. Nodocephalosaurus kirtlandensis is from the Upper Cretaceous Kirtland Formation, De-na-zin Member, now considered to be late Campanian in age. Previously collected ankylosaurid material, from the Kirtland Formation, may pertain to this taxon rather than Euoplocephalus or Panoplosaurus, but this cannot be determined with certainty.

REDESCRIPTION OF THE CERATOPSID DINOSAUR TOROSAURUS UTAHENSIS (GILMORE, 1946) AND A REVISION OF THE GENUS

Abstract The holotype of the ceratopsid dinosaur Torosaurus (=Arrhinoceratops?) utahensis (Gilmore, 1946) consists of a right squamosal, jugal, quadrate, quadratojugal, epijugal, lacrimal, and postorbital horncore/orbital region. Some elements previously described by Gilmore (1946), notably the epoccipitals and parietals, were not originally included, so they cannot be considered part of the holotype. Associated elements (lower jaws and others), which may pertain to the holotype, are described for the first time; they, too, are not formally considered part of the type material, but they provide additional information regarding the osteology of this rare chasmosaurine. Torosaurus utahensis differs from T. latus (type species) in having a squamosal that is shorter and squared-off at its distal end and an unusually expanded horncore base that lies above and anterior to the orbit. In contrast, T. latus has unusually long, attenuated triangular squamosals and a more restricted horncore base. The otic notch is more open in T. utahensis than T. latus. The genus Torosaurus is distinguished from other chasmosaurine genera by a combination of characters including a broad, thin, sheetlike parietal with relatively small, nearly circular fenestrae and broad median parietal bar; convex posterior margin of parietal; and relatively straight postorbital horncores that are oval (elliptical) in cross section. Bona fide records of T. latus from Montana, South Dakota, and Wyoming are from strata of Lancian (late Maastrichtian) age. Previous reports of Torosaurus from the Naashoibito Member of the Ojo Alamo Formation (Lehman, 1981, 1985, 1996) in the San Juan Basin and the McRae Formation (Lucas et al., 1998), New Mexico, as well as the single Torosaurus record from Saskatchewan (Tokaryk, 1986), are based on specimens that can at best be identified as Chasmosaurinae genus indeterminate, because they lack derived features of the taxon. Putative Torosaurus specimens from the Big Bend region of Texas (Lawson, 1976; Lehman, 1996) are also considered as indeterminate chasmosaurines. All records of Torosaurus are Maastrichtian in age, but records of T. utahensis appear to be older than those of T. latus.

A NEW GENUS, PARAPLACOSAURIOPS (SQUAMATA, ANGUIDAE, GLYPTOSAURINAE), FROM THE EOCENE OF FRANCE

Abstract Paraplacosauriops, gen. nov., is a ‘melanosaurin’ glyptosaurine lizard based on two isolated, nearly complete maxillae from the middle Eocene of France. Paraplacosauriops is known by one species, Paraplacosaurus quercyi (Filhol), a species previously included in the glyptosaurin genus Placosaurus. The taxon Paraplacosauriops quercyi is characterized by an unique heterodont dentition, consisting of large, crushing teeth in both the maxilla and neotype dentary. The dentary is further distinguished by a well-developed intramandibular septum fused to the ventral margin of the Meckelian canal. Paraplacosauriops is known with certainty from the middle Eocene (Lavergne, Phosphorites du Quercy). Fragmentary specimens from the early Eocene (Dormaal, Belgium) are provisionally referred to this taxon. The species Xestops abderhaldeni and X. weigelti are not referable to the genus Xestops and are formally synonymized with each other as Placosauriops weigelti.

ALAMOSAURUS (DINOSAURIA: SAUROPODA) FROM THE LATE CAMPANIAN OF NEW MEXICO AND ITS SIGNIFICANCE

The titanosauridAlamosaurus sanjuanensis Gilmore, 1922, has long been known as the last North American sauropod; its fossils from Wyoming, Utah, New Mexico and Texas have been generally agreed to be of Lancian (late Maastrichtian) age (Hunt and Lucas, 1992, 1993; Lehman, 1980; Lucas, 1980; Lucas et al. 1987; Lucas and Hunt, 1989). Lucas and Hunt (1989) coined the term ‘‘sauropod hiatus’’ to refer to the Cenomanian–late Maastrichtian absence of sauropods in North America, arguing that it resulted from the extirpation of sauropods in North America at about the end of the Albian, followed by their immigration (probably from South America) during the late Maastrichtian. During the summer of 1998, one of us (RMS) collected an incomplete sauropod tooth from the De-na-zin Member of the Kirtland Formation (Fig. 1). We refer this tooth toAlamosaurus sanjuanensis based on the earlier report of Kues et al. (1980), although we note that the type specimen ofA. sanjuanensis lacks cranial material (Gilmore, 1922). In addition, we recently have identified uncataloged, and heretofore undocumented, sauropod vertebrae, collected by a University of New Mexico (UNM) field party during 1984 from the same stratigraphic interval. We recognize that Alamosaurus is a form genus, to which we provisionally refer all Late Cretaceous sauropod material from the San Juan Basin, pending the discovery of diagnostic material. Here, we document this important new material of late Campanian age, thus shortening the ‘‘sauropod hiatus.’’ Moreover, these new records undermine the use of Alamosaurus (or sauropods in general) as an index fossil of Lancian time and thus may call into question the age of the Naashiobito Member of the Kirtland Formation. Institutional Abbreviations: NMMNH, New Mexico Museum of Natural History and Science, Albuquerque; SMP, The State Museum of Pennsylvania, Harrisburg; USNM, United States National Museum of Natural History, Washington, D.C.

Redescription of the holotype of Placosaurus rugosus gervais 1848–1852 (Squamata, Anguidae, Glyptosaurinae) from the Eocene of France and a revision of the genus

Abstract The European-Asian taxon Placosaurus is a distinct glyptosaurine lizard that differs from the North American glyptosaurine genera Glyptosaurus, Helodermoides, Paraglyptosaurus, and Proglyptosaurus. Presently, species of Placosaurus can only be discriminated based on frontal morphology. Three species are recognized: Placosaurus rugosus Gervais, 1848–1952, Placosaurus estesi, sp. nov., and Placosaurus mongoliensis, all based on frontal material. Although the Asian species P. mongoliensis is retained in the genus Placosaurus, we consider this taxonomic assignment tentative. The species P. cayluxi, P. galliae, P. gaudryi, and P. margariticeps are considered nomina dubia. “Placosaurus” europaeus, based on a dentary with teeth, is tentatively retained in the genus Placosaurus but this generic assignment is equivocal. The species “P.” quercyi pertains to a new ‘melanosaurin’ and not to Placosaurus.

BRACHYCHAMPSA MONTANA GILMORE (CROCODYLIA, ALLIGATOROIDEA) FROM THE KIRTLAND FORMATION (UPPER CAMPANIAN), SAN JUAN BASIN, NEW MEXICO

Abstract Three new specimens of the rare alligatoroid Brachychampsa montana from the upper Campanian Kirtland Formation (De-na-zin Member), San Juan Basin, New Mexico, are the first bona fide examples of this taxon from this stratigraphic interval. The most complete specimen (SMP VP-1312) consists of much of the skull table and snout and a nearly complete mandible. SMP VP-1264 consists solely of an incomplete partial skull table (parietal, right squamosal), partial basicranium (basioccipital, otoccipital), and incomplete right quadrate, whereas NMMNH P-7988 is an isolated frontal. Together, these new specimens supplement and allow for further comparison to other globidontans and to previously documented specimens of Brachychampsa. ?Brachychampsa sealeyi, from the Menefee Formation of the San Juan Basin, New Mexico, is based on a juvenile specimen that cannot be distinguished from B. montana, so it is a subjective junior synonym. The crocodylian assemblage of the Kirtland Formation consists of Brachychampsa montana, Leidyosuchus sp. and Denazinosuchus kirtlandicus. It is doubtful that tooth morphology alone can be correlated with “cheloniphagous” diet within the globidontans.

The type locality ofCoelophysis, a Late Triassic dinosaur from north-central New Mexico (USA)

KurzfassungDer Dinosaurierfundpunkt an der Ghost Ranch ist nicht die Typ-Lokalität einer der drei benannten Arten des spättriadischen CeratosaurierCoelophysis (Dinosaurier; Saurischia: Theropoda). Neu entdeckte Fundpunkte spättriadischer Ceratosaurier in der Nähe der Ghost Ranch passen dagegen besser zu der geographischen und stratigraphischen Beschreibung des ErstentdeckersDavid Baldwin. Darüber hinaus stimmen Erhaltung und Morphologie der Ceratosaurier der neuen Fundpunkte besser mit dem Originalmaterial vonBaldwin überein als das Material der Ghost Ranch. Wir nehmen daher an, daß die neuen FundpunkteBaldwins ursprüngliche Fundpunkte sind; damit werden die neuen Funde zu Topotypen vonCoelophysis. Diese Topotypen zeigen, daß sichCoelophysis deutlich vonRioarribasaurus, einem Dinosaurier von der Ghost Ranch, unterscheidet.AbstractThe dinosaur quarry at Ghost Ranch is not the type locality of any of the three named species of the Late Triassic ceratosaurian dinosaurCoelophysis (Saurischia: Theropoda). Instead, newly discovered localities near Ghost Ranch that produce Late Triassic ceratosaurs match the geographic and stratigraphic description of two of theCoelophysis type localities provided byDavid Baldwin, the original collector. Furthermore, the preservation and morphology of ceratosaur fossils from the new localities more nearly matchesBaldwin’s original material than does the Ghost Ranch quarry material. We conclude that these new localities encompassBaldwin’s localities, so the newly collected ceratosaur fossils from these localities are probable topotypes ofCoelophysis. These topotypes preserve unique morphology that suggestsCoelophysis is a taxon distinct fromRioarribasaurus, the Ghost Ranch dinosaur.