AN ARTICULATED POPOSAURID RAUISUCHIAN ARCHOSAUR FROM THE LATE TRIASSIC DEEP RIVER BASIN, NORTH CAROLINA

PEYER Karin and CARTER Joseph G., Department of Geological Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, SUES Hans-Dieter Department of Palaeobiology, Royal Ontario Museum, Toronto, ON M5S 2C6, Canada, OLSEN Paul E. Lamont-Doherty Earth Observatory of Columbia University, Palisade, NY 10964

A poposaurid from Late Triassic age strata of the Durham sub-basin of the Deep River Basin, North Carolina, is the first articulated rauisuchian skeleton recorded from the eastern United States. The skeleton is excellently preserved and largely uncompressed, with a postcranium that is nearly seventy percent complete. The pelvic girdle is incompletely known and only includes the distal footed ends of the pubes, plate-like ischia, and a posterior ventral portion of the right ilium. Present are a nearly complete manus, ulna, radius, humerus, pes, tibia, fibula, distal right femur, interclavicle, proximal part of the scapulocoracoid, several vertebrae and ribs, a few chevron bones, and virtually the entire gastralia. The dermal armor consisted of cervical and dorsal, imbricated, paired, paramedian osteoderms and, on the tail, smaller, oak-leaf shaped osteoderms. Some of the skeletal remains show post-mortem borings produced by the trace fossil Scoyenia. The massive pectoral girdle and extended arms and tightly bound metacarpals suggest that the forelimbs were generally active in locomotion. Although the present taxon is closely related to Postosuchuskirkpatricki Chatterjee, 1985 it clearly differs in several characters of the hand, massiveness of the supra-acetabular buttress in the scapulocoracoid, stronger iliofibularis trochanter, and more blade-like ischium. The vertebral column, including ribs and osteoderms in Rauisuchus tiradentes Huene, 1942, is strikingly similar to the North Carolina taxon. Larger members of the Rauisuchia such as Fasolasuchus tenax Bonaparte, 1978 and Saurosuchus galilei Reig, 1959 seem to be more distantly related. The North Carolina taxon is in many ways more autapomorphic than Ticinosuchus ferox Krebs, 1965 but not as specialized anatomically as Chatterjee elegans Long and Murry, 1995.