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A NEW SUCHIAN ARCHOSAUR FROM THE UPPER TRIASSIC OF NORTH CAROLINA
A partial but largely articulated skeleton of a ‘rauisuchian’ archosaur from Late Upper Triassic strata of the Durham sub-basin, Deep River basin, Newark Supergroup, North Carolina, represents a new species of Postosuchus Chatterjee, 1985. It represents the first record of this taxon from eastern North America. The well preserved specimen includes cranial bones, a largely articulated right manus, right and left pedes, pubes, axis, several postaxial cervical, dorsal, and caudal vertebrae, chevron bones, osteoderms, interclavicle, clavicles, cervical ribs, a sacral rib, and a complete set of gastralia. The skeletal elements are described and compared to those of other ‘rauisuchians’. An apparant autapomorphy of Postosuchus alisonae includes a well developed flange on the proximal portion of metacarpal II fitting into strongly proximally grooved metacarpal I. The new specimen includes many bones previously unknown for Postosuchus and it allows a more complete differentiation of Postosuchus from other ‘rauisuchian’ genera. Diagnostic features of this genus include an axis with two ventral keels; postaxial cervical centra with strongly developed single ventral keels that are anteriorly and/or posteriorly extended into hypapophyses; short ribs on the anterior cervical vertebrae; heart-shaped cervical neural ‘spine tables’; a subrectangular, relatively short coracoid; and proportionately short manus with dorsoventrally compressed, reduced, blunt unguals on manual digits III and IV. Morphological comparisons indicate a close relationship between Postosuchus and Batrachotomus and possibly also Tikisuchus.
Skeletal reconstruction of Postosuchus alisonae based on the preserved elements of UNC 15575 (holotype). Preserved bones are shown in black. The reconstruction of the skull and pelvic bones are based on Postosuchus kirkpatricki (TTUP 9002). Scale bar equals 50 cm.