Systematics of the Rubidgeinae (Therapsida: Gorgonopsia)

Abstract

The subfamily Rubidgeinae, containing the largest known African gorgonopsians, is thoroughly revised. Rubidgeinae is diagnosed by the absence of a blade-like parasphenoid rostrum and reduction or absence of the preparietal. Seven rubidgeine species from the Karoo Basin of South Africa are recognized as valid: Aelurognathus tigriceps, Clelandina rubidgei, Dinogorgon rubidgei, Leontosaurus vanderhorsti, Rubidgea atrox, Smilesaurus ferox, and Sycosaurus laticeps. Rubidgeines are also present in other African basins: A. tigriceps and S. laticeps occur in the Upper Madumabisa Mudstone Formation of Zambia, and D. rubidgei, R. atrox, and the endemic species Ruhuhucerberus haughtoni comb. nov. and Sycosaurus nowaki comb. nov. occur in the Usili Formation of Tanzania. Aelurognathus nyasaensis from the Chiweta Beds of Malawi also represents a rubidgeine, but of uncertain generic referral pending further preparation. No rubidgeine material is known outside of Africa: the purported Russian rubidgeine Leogorgon klimovensis is not clearly referable to this group and may not be diagnosable. Phylogenetic analysis of rubidgeines reveals strong support for a clade (Rubidgeini) of advanced rubidgeines including Clelandina, Dinogorgon, Leontosaurus, and Rubidgea. Support for Smilesaurus as a rubidgeine is weak; it may, as previous authors have suggested, represent an independent evolution of large body size from an Arctops-like ancestor. Temporally, rubidgeines are restricted to the Late Permian, first appearing in the Tropidostoma Assemblage Zone and reaching highest diversity in the Cistecephalus and Daptocephalus assemblage zones of the Beaufort Group.