New Material of Microgomphodon oligocynus (Eutherapsida, Therocephalia) and the Taxonomy of Southern African Bauriidae

Abstract

An exceptionally well-preserved specimen of the bauriid therocephalian Microgomphodon oligocynus from the Burgersdorp Formation (Early-Middle Triassic, Cynognathus Assemblage Zone) of the South African Karoo is described. In addition, a taxonomic revision of bauriid therocephalians from southern Africa, based on firsthand examination of almost all know specimens, is presented. Microgomphodon oligocynus and Bauria cynops are recognized as the only valid species of southern African bauriids. Microgomphodon oligocynus is differentiated from B. cynops on the basis of clear-cut morphological features such as the presence of a complete postorbital bar, pineal foramen, contribution of the vomer to the osseous secondary palate, comparatively large orbits, presence of a lateral fossa on the posterior portion of the horizontal ramus and on the coronoid process of the dentary, and reduced number of postcanines. Procrustes analysis of the two best-preserved specimens of these species allowed recognition of further shape differences: M. oligocynus has a taller but narrower cranium, taller snout, temporal opening more expanded laterally, pterygoid process located more anteriorly, and smaller suborbital vacuity. The mandible of M. oligocynus has a higher symphysis, relatively short corpus, and more laterally-directed coronoid process. Microgomphodon oligocynus is known from the Olenekian to what are probably late Anisian levels in South Africa and Namibia, whereas B. cynops is restricted to the early Anisian of South Africa.