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.
Highlights
Gorgonopsians are among the most iconic of Permian animals, and feature prominently in popular literature on the period (e.g., Ward, 2004)
In the last 50 years, only a handful of papers have been published on the African record of Gorgonopsia, our primary source of data on the group (Kemp, 1969; Sigogneau, 1968; Sigogneau, 1970; Cruickshank, 1973; Parrington, 1974; Sigogneau-Russell, 1989; Laurin, 1998; Maisch, 2002; Gebauer, 2014; Kammerer, 2014; Kammerer, 2015; Kammerer et al, 2015)
Comprehensive taxonomic revision of rubidgeine gorgonopsians has greatly reduced the number of valid taxa from 36 nominal species to the nine recognized here
Summary
Gorgonopsians are among the most iconic of Permian animals, and feature prominently in popular literature on the period (e.g., Ward, 2004). The parietal is a relatively short component of the skull roof, but bears an elongate posterior process that typically mirrors the dorsal ramus of the postorbital (Fig. 1A) This process extends onto the occiput, between the tabular and squamosal, in Aelurognathus (Fig. 2B), Smilesaurus, and Sycosaurus. Aelurognathus can be distinguished from Smilesaurus by the following features shared with all other rubidgeines: absence of a frontal contribution to the orbit, expanded postorbital bar, and thickened dorsal margin of the orbit and temporal fenestra It can be distinguished from Smilesaurus by the long, narrow parasphenoid rostrum (a primitive retention), proportionally smaller canine, bulbous snout, anteriorly bulbous interchoanal body, and presence of 4–6 upper postcanines. Robust support was recovered for the genus Sycosaurus (80/2), the clade containing Clelandina, Dinogorgon, and Rubidgea (85/3), and the clade containing all rubidgeines other than Smilesaurus (71/3)
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