Postcranial morphology of the South African middle Permian pareiasaurs from the Karoo Basin of South Africa

Abstract

Pareiasaurs were relatively abundant and globally distributed herbivorous parareptiles of the middle to late Permian. The basal-most pareiasaurs, the Bradysauria, are restricted to the middle Permian of South Africa and went extinct at the end of the Guadalupian (Capitanian) at the top of the Tapinocephalus Assemblage Zone. Currently, three genera are recognized in this group: Bradysaurus, Embrithosaurus and Nochelesaurus, but their postcrania are poorly known, and consequently poorly understood. In this paper, our third contribution designed to improve understanding of the Bradysauria, we present a detailed comparative postcranial description and updated diagnoses for Bradysaurus baini, Embrithosaurus schwarzi and Nochelesaurus alexanderi. Bradysaurus baini has one postcranial<br />autapomorphy: anterior dorsal osteoderms smooth and strongly convex, with an incipient central boss, and very light ornamentation. Three pelvic autopomorphies of Embrithosaurus schwarzi are confirmed: anterior portion of the iliac blades flat and vertical (not everted<br />or upturned); iIiac blades diverge anteriorly, oriented at 45?60° off the sagittal plane; and a very thick pelvic symphysis. For Nochelesaurus alexanderi we remove all three of the postcranial autapomorphies previously proposed. To the diagnoses of each species, we have added several new distinguishing postcranial features, within the local group of middle Permian pareiasaurs. The results reinforce our previous cranial studies concluding that three valid species of pareiasaurs are represented in the South African middle Permian.