INTRODUCTION

In the early 1960s, Petrified Forest National Park naturalist Phillip Van Cleave collected the fragmentary postcranial remains of a small reptile. This specimen was originally listed by Murry and Long (1989) as a possible proterochampsid based in part on the morphology of a second specimen comprised of a right mandible and other fragmentary skull elements that had been collected by Charles Camp from the same area in 1923. Subsequently, Long and Murry (1995) recognized that the two specimens were not from the same taxon, and named two new taxa based on the material, designating the partial skull as the holotype of Acallosuchus rectori and the postcranial material as the holotype of Vancleavea campi. Long and Murry (1995) were unsure of the phylogenetic relationships of these taxa and conservatively assigned them both to Neodiapsida incertae sedis.

In recent years, Vancleavea has received more attention because of the discovery and recognition of additional material from the Late Triassic of New Mexico and Texas. In particular two articulated skeletons from the Coelophysis Quarry at Ghost Ranch, New Mexico, were assigned to Vancleavea by Hunt et al. (2002) (see also Small and Downs 2002). These skeletons are currently being described (Nesbitt et al. in review). Hunt et al. (2002) also provided an overview of all identified Vancleavea material and discussed the distribution of the taxon. This material includes a partial skeleton and isolated material reported by Polcyn et al. (2002) from the Chinle Formation near St. Johns, Arizona. Hunt et al. (2005) published the first photographs of the holotype of Vancleavea campi and provided a more detailed description and discussion of the distribution of the taxon than that provided by Long and Murry (1995) and Hunt et al. (2002). Here, we describe two new partial skeletons of Vancleavea from the Petrified Forest Member of the Chinle Formation in Petrified Forest National Park (PEFO) and further discuss the phylogenetic relationships of the taxon based on this new material. These specimens are referable to Vancleavea as they both possess the diagnostic keeled osteoderms that are characteristic of the genus (Long and Murry 1995; Hunt et al. 2002) and represent the best preserved material of Vancleavea from the Petrified Forest Member of the Chinle Formation. Because the type specimen of Vancleavea campi is fragmentary, it is desirable to supplement the original description of the taxon with other specimens from PEFO to assist other workers currently working on descriptions of material that have been tentatively referred to Vancleavea (e.g., the Ghost Ranch specimens).

Institutional Abbreviations. MNA, Museum of Northern Arizona, Flagstaff, USA; PEFO, Petrified Forest National Park, Arizona, USA; PFV, Petrified Forest National Park Fossil Vertebrate Locality; SAM-PK, South African Museum of Natural History, Cape Town, South Africa; UCMP ; University of California Museum of Paleontology, Berkeley, USA; USMN ; United States National Museum, Washington D.C., USA.