UNCOVERING THE CRETACEOUS TERRESTRIAL VERTEBRATE RECORD OF SUB-SAHARAN AFRICA: NEW INFORMATION FROM THE MIDDLE CRETACEOUS GALULA FORMATION, RUKWA RIFT BASIN (EAST AFRICAN RIFT SYSTEM), SOUTHWESTERN TANZANIA

The Cretaceous terrestrial vertebrate record from the Southern Hemisphere has improved dramatically over the past 20 years. Nonetheless, large gaps remain with regard to major regions of Gondwana. Principal among the latter is Afro-Arabia, the large, central portion of the former supercontinent. Whereas the northern half of this landmass preserves both marine and continental sequences of Cretaceous age and yields a respectable fossil record, the southern half of the continent does not. During this time most of southern Africa existed as a stable platform with the development of minimal accommodation space, resulting in few significant continental deposits and any associated fossils. Hence, any new information from this fossil-depauperate region will have immediate impact for evaluating paleobiogeographic models, not to mention providing a basis for characterizing how large-scale landform dynamics (e.g., rifting, uplift) and any climatic sequelae have influenced biotic evolution during the Cretaceous. Annual expeditions since 2002 to the Rukwa Rift Basin in southwestern Tanzania have resulted in the recovery of a novel and diverse Cretaceous terrestrial vertebrate fauna from the middle Cretaceous Galula Fm. These expeditions have revealed extensive outcrops with vertebrate fossils along a series of drainages excising through rift flank sequences. Fossils recovered to date represent of all major vertebrate clades, including fishes, crocodyliforms, dinosaurs, and the most complete mammal yet recovered from Continental Africa. Notable among them are 4 taxa each of saurischian dinosaurs and notosuchian crocodyliforms, both of which represent ideal groups for integrating into current models aimed at understanding large-scale biogeographic patterns. Specifically, the presence of both notosuchian crocodyliforms and titanosaurian sauropods that are most closely related to geographically proximate clademates from the Dinosaur Beds of Malawi suggests a regional endemism signal during the middle Cretaceous. Ongoing work will further constrain a number of novel tectono-sedimentary relationships in the region and characterize the developing faunas, floras, and paleoenvironments for integration into biogeographic and climatic models related to the Cretaceous of Gondwana.