A basal anomodont therapsid from the lower Beaufort Group, Upper Permian of South Africa

Abstract

ABSTRACT The skull of the basal anomodont therapsid Anomocephalus africanus, from the Tapinocephalus Assemblage Zone of the Beaufort Group, Upper Permian of South Africa, is described in detail. Anomocephalus is characterized by the possession of two premaxillary teeth, blunted, peg-like anterior teeth, cheek teeth with saddle-shaped tips, and the presence of a tall coronoid process. Anomocephalus is the most basal member of Anomodontia because it lacks three unambiguous and six ambiguous synapomorphies present in all other anomodonts. This basal position provides compelling support for the hypothesis that anomodonts originated in Gondwana and later dispersed into Euramerica and elsewhere across Pangea. Minimum divergence times suggest strongly that anomodonts were diversifying in central Gondwana well before the onset of Beaufort sedimentation. Accordingly, the absence of terrestrial vertebrates in the Ecca Group is most likely an artifact of preservational bias.