SOUTHERN AFRICAN BAURIIDAE (THERIODONTA, EUTHERAPSIDA): IMPLICATIONS FOR EARLY-MIDDLE TRIASSIC BIOSTRATIGRAPHY

VAN DEN HEEVER, J.; ABDALA, F.; RUBIDGE, B. S.

Congreso; SIXTY-NINTH ANNUAL MEETING SOCIETY OF VE RTEBRATE PALEONTOLOGY AND THE FIFTY-SEVENTH SYMPOSIUM OF VERTEBRATE PALAEONTOLOGY AND COMPARATIVE ANATOMY (SVPCA); 2009

SOCIETY OF VE RTEBRATE PALEONTOLOGY

Baurids are the youngest ?therocephalian? representatives in southern Africa, being known from the late Early to the early Middle Triassic deposits of the Karoo Basin in South Africa and of the upper Omingonde Formation in Namibia. In this contribution we present a new bauriid specimen from the Cynognathus Assemblage Zone of the Karoo Basin, the best preserved of all the representatives of this group. The new material is an almost complete skull with lower jaw, five cervical vertebrae with ribs and a right manus. Unexpected features of this specimen, such as the participation of the vomer in the posterior margin of the secondary osseous palate and the presence of a dorsoventrally high parasphenoidal keel in the anterior portion of the basicranium, provide fresh morphological information about this group. Our taxonomic review of the southern African Bauriidae, based on first hand examination of most of the known specimens of this group, indicates that only two morphotypes are represented. The small-sized Microgomphodon oligocynus (including Sesamodon browni, Melinodon simus, Watsoniella breviceps and Herpetogale marsupialis) which, in addition to the features previously mentioned, has a complete postorbital bar and pineal foramen. The second morphotype, Bauria cynops, is larger and lacks the above mentioned features of M. oligocynus. Analysis of the geographic distribution of Bauriidae in southern Africa, indicate that both species occur in Subzone B of the Cynognathus Assemblage Zone in the southwestern portion of the Karoo Basin. In addition, M. oligocynus is also known from the older Subzone A of the Cynognathus Assemblage Zone in the northern portion of the Karoo Basin, as well as from the higher stratigraphic horizons of the upper Omingonde Formation of Namibia.