Abstract

The skull of a carnivorous therapsid from the Tapinocephalus Assemblage Zone of the Beaufort Group, Middle Permian of South Africa, is described as a new burnetiamorph biarmosuchian. Pachydectes elsi n. gen. and sp. is distinguished from all other therapsids by its possession of a conspicuous pachyostotic maxillary boss that sheathes the root of the upper canine. It shares the presence of a preparietal ossification with other biarmosuchians and a pachyostotic boss below the postorbital bar with other burnetiamorphs. Pachydectes is the first burnetiamorph known from along the Ecca-Beaufort contact in the eastern part of the Karoo Basin and only the second burnetiamorph to be described from the Tapinocephalus Assemblage Zone. All other South African burnetiamorphs, save Bullacephalus jacksoni, are known from much younger biozones of the Beaufort Group. Our phylogenetic analysis links Pachydectes and Bullacephalus, which are the stratigraphically lowest-occurring taxa, with Burnetia, the burnetiamorph known from the highest position in the lower Beaufort Group. This result suggests that most of the history of biarmosuchians in South Africa is unrecorded.

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