CONTINENTAL VERTEBRATES FROM THE LATE OLIGOCENE NSUNGWE FORMATION (SOUTHWESTERN TANZANIA) AND FAUNAL DYNAMICS IN SUB-SAHARAN AFRICA DURING THE PALEOGENE-NEOGENE TRANSITION

Field and laboratory studies of Red Sandstone Group strata in the Rukwa Rift of southwestern Tanzania document a complex basin history with at least three time-distinct tectonic and depositional events, represented by alluvial fans transitioning into fluvial and lacustrine depositional environments during the Cenozoic. Localities in the late Oligocene Songwe Member of the Nsungwe Formation predominantly preserve microfauna including rodents, macroscelideans, hyracoids, and small strepsirrhine and anthropoid primates, together with crocodylians, lepidosaurians, anurans, and a variety of invertebrates. These facies are dated at ~25 MYA using both radiometric dating of intercalated tuffs and detrital zircon geochronology. The Nsungwe 2B locality has revealed an increasingly diverse array of specimens including fossils commonly found in other localities such as micromammals, fishes, invertebrates and anurans, in addition to many larger specimens including two new catarrhine primate taxa. Nsungwe Formation discoveries offer a glimpse at the evolutionary history of late Oligocene terrestrial and freshwater habitats in eastern Africa, providing data on the complex tectono-sedimentary history of the Rukwa Rift Basin. Continued exploration offers a new window into the Paleogene-Neogene transition on continental Africa, with expanded opportunities for recognizing paleobiological diversity by sampling different habitat types within the region.