543 Harris et al., eds., 2006, The Triassic-Jurassic Terrestrial Transition. New Mexico Museum of Natural History and Science Bulletin 37. REINTERPRETATION OF THE HOLOTYPE OF MALERISAURUS LANGSTONI, A DIAPSID REPTILE FROM THE UPPER TRIASSIC CHINLE GROUP OF WEST TEXAS JUSTIN A. SPIELMANN 1 , SPENCER G. LUCAS 1 , ADRIAN P. HUNT 1 AND ANDREW B. HECKERT 2 1 New Mexico Museum of Natural History and Science, 1801 Mountain Rd., Albuquerque, NM 87104-1375; 2 Department of Geology, Appalachian State University, ASU Box 32067, Boone, NC 28608-2067 Abstract—The holotype of Malerisaurus langstoni from the Late Triassic (Otischalkian) Trilophosaurus quarry 2 of West Texas is a chimera. The holotype represents at least 6-7 individuals of four reptilian groups: Trilophosauridae, Rhynchosauridae, Parasuchidae and Aetosauria. The majority of the material, including all of the cranial fragments, are re-identified as Trilophosaurus buettneri. Based on the chimeric nature of the specimen, the holotype of M. langstoni is restricted to the skull fragments and considered a junior subjective synonym of T. buetterni. This reassessment of M. langstoni calls into question the validity of M. robinsonae from the Maleri Formation in India and suggests that at least some of the elements referred to this taxon may, in fact, be a record of Trilophosaurus. This would extend the paleogeographic range of Trilophosaurus from a taxon endemic to the American Southwest to a nearly Pangean distribution during the Late Triassic. INTRODUCTION Malerisaurus langstoni is a Late Triassic (Otischalkian) diapsid reptile known only from a single partial skeleton, the holotype, collected from Trilophosaurus quarry 2. Located in Howard County, West Texas, 25 km southeast of Big Spring, the Trilophosaurus quarries in the Colo- rado City Formation of the Chinle Group (Fig. 1; Lucas et al., 1993; Lucas and Anderson, 1993) have been among the most important Late Triassic bonebeds in the American Southwest since their initial excava- tion and collection between 1939 and 1941 by the Work Projects Admin- istration (WPA). Over the last 60-plus years, studies of the material from the various Trilophosaurus quarries have focused on osteology (Gregory, 1945; Parks, 1969; Demar and Bolt, 1981), taphonomy of the quarry and paleoecology (Elder 1978, 1987), and the quarries’ faunal composition with regard to its biostratigraphic utility (Hunt and Lucas, 1993; Lucas et al., 1993; Long and Murry, 1995). Indeed, the vertebrate fauna of the Trilophosaurus quarries is the “type” fauna of the Otischalkian land-vertebrate faunachron (lvf) of Hunt and Lucas (1993). Malerisaurus langstoni, a member of this fauna, has only been examined in detail once, in its initial description by Chatterjee (1986). In his description, Chatterjee compared the holotype of M. langstoni to the holotype and paratype of Malerisaurus robinsonae, a diapsid reptile from the Maleri Formation of India also initially described by Chatterjee (1980). Nevertheless, our examination of the holotype of M. langstoni identifies it as a chimera, consisting of the skull, axial skeleton and femora of the archosauromorph Trilophosaurus buettneri, which are locally abun- dant in quarry 2, the humeri of the rhynchosaur Otischalkia elderae, a probable aetosaur braincase and portions of a juvenile phytosaur. Here, we also photographically illustrate key elements of the holotype of M. langstoni for the first time, including the skull, braincase, axial skeleton, humerus and femur. In this paper, TMM = Texas Memorial Museum, Austin. THE HOLOTYPE OF MALERISAURUS LANGSTONI Chatterjee (1986) described the holotype of Malerisaurus langstoni, TMM 31099-11, as a nearly complete skeleton of a single individual consisting of: cranial elements; a braincase; vertebrae 2 through 8 (cervical), 10 through 25 (dorsal), 26 and 27 (sacral), 30 (proximal caudal) and 37 (distal caudal); interclavicle; shoulder girdle; humerus; radius; pelvis; femur; and tibia. We focus our discussion on the skull elements, braincase, axial skeleton, humerus and femur, all of which have diagnostic value and are generally distinct between Late Triassic reptile taxa. Skull The skull of M. langstoni (Fig. 2) is incomplete. Chatterjee (1986, p. 298) interpreted the elements present as “the posterior half of the skull roof, quadrate, left jugal, and right mandible…held together in ma- trix.” In Chatterjee’s (1986, fig. 2) diagrams of the skull there are three distinct groups of elements: the parietal/quadrate, the postorbital and the lower jaw. The initial identifications of Chatterjee (1986) will hereafter be placed in quotation marks, whereas our current interpretation will be without quotes. FIGURE 1. Index map and stratigraphic column showing the location of Trilophosaurus quarry 2 within the Late Triassic stratigraphy of West Texas.