Taxonomic revision and new observations on the postcranial skeleton, biogeography, and biostratigraphy of the dicynodont genus Dicynodontoides, the senior subjective synonym of Kingoria (Therapsida, Anomodontia)

Abstract

ABSTRACT The postcranial skeleton of Kingoria is well-described, and previous authors noted the taxon's divergent pectoral, pelvic, and femoral morphologies. Yet, humeral morphology of Kingoria has remained enigmatic because of poor preservation and the absence of published descriptions. Here we describe new, nearly complete humeri of Kingoria collected from the Upper Permian Usili Formation, Ruhuhu Basin, Tanzania. These specimens demonstrate that the humeral morphology of K. nowacki is much more conservative than that of its pelvis or femur. There is evidence of increased importance for long-axis rotation of the humerus in K. nowacki, and the trochlea and the capitellum are partially separated, but these morphologies are not taken to the extremes observed in cistecephalid dicynodonts. Surprisingly, the new Tanzanian humeri differ from South African specimens: the best-preserved South African specimen is more gracile, with different humeral head and deltopectoral crest morphologies. We use these differences, along with new observations on skull morphology, tusk frequency, pelvic and fibular morphology, and body size to revise the taxonomy of Kingoria. Kingoria is shown to be a junior synonym of Dicynodontoides Broom, 1940, and two species are recognized: D. recurvidens from South Africa and D. nowacki from Tanzania. Finally, we review the stratigraphic and geographic ranges of Dicynodontoides, and document new occurrences in the Pristerognathus and Tropidostoma assemblage zones of the Karoo Basin, as well as its presence in the Chiweta Beds of Malawi.