CRANIAL OSTEOLOGY OF HYPSOGNATHUS FENNERI, A LATEST TRIASSIC PROCOLOPHONID REPTILE FROM THE NEWARK SUPERGROUP OF EASTERN

Based primarily on two previously undescribed skulls, this paper presents a detailed description of the skull and mandible of the latest Triassic procolophonid reptile Hypsognathus fenneri Gilmore, 1928. One of the new skulls, belonging to a presumed juvenile, clearly establishes for the first time the sutural pattern, which differs signif- icantly from that in Procolophon and more basal procolophonid taxa. A number of shared derived features in the structure of the skull and mandible indicate that Hypsognathus is closely related to Leptopleuron from the Upper Triassic Lossiemouth Sandstone Formation of Scotland. Hypsognathus had a wide geographic and stratigraphic distri- bution in eastern North America during the latest Triassic (Norian-Rhaetian).