A single isolated parietal bone from the Fort Sill deposit of Oklahoma is described. It has a well-developed upper temporal opening, resembling that of the primitive South African diapsids. The parietal is compared with that of Araeoscelis and Youngopsis. Based on comparison with this parietal and the configuration of the rear skull table of millerosaurs and romeriids, the bone usually identified as tabular in younginids is designated the supratemporal. The Fort Sill parietal may belong to a form structurally, if not phylogenetically, intermediate between primitive captorhinomorphs and eosuchians.