The second titanosaurian (Dinosauria: Sauropoda) from the middle Cretaceous Galula Formation, southwestern Tanzania, with remarks on African titanosaurian diversity

ABSTRACT

The paleobiogeographic significance of continental Africa during the middle and Late Cretaceous is not well understood, in part due to incomplete sampling from large portions of the landmass during these intervals. Intensified field efforts in the Galula Formation exposed in southwestern Tanzania have revealed a diverse vertebrate fauna, including the novel titanosaurian Shingopana songwensis, gen. et sp. nov., described herein. Based on a left angular, cervical vertebrae, cervical and dorsal ribs, a left humerus, and a partial left pubis, Shingopana exhibits morphology indicating affinities with the Late Cretaceous aeolosaurine titanosaurians of South America. The bulbous expansion of the cervical vertebral neural spine is similar to the condition in Bonitasaura salgadoi, Overosaurus paradasorum, and Trigonosaurus pricei. The dorsal ribs of Shingopana also present proximal anterior and posterior flanges that previously were proposed to be unique to Overosaurus. Furthermore, Shingopana is diagnosed by a divided spinoprezygapophyseal lamina in the middle-to-posterior cervical vertebrae. Parsimony and both uncalibrated and tip-dated Bayesian phylogenetic approaches support Shingopana as the first African titanosaurian that is closely related to aeolosaurines. Comparisons with other African titanosaurians, such as the co-occurring Rukwatitan bisepultus and geographically proximate Malawisaurus dixeyi, suggest that southern African forms represent diverse taxa rather than forming a monophyletic group. Moreover, southern African forms exhibit stronger affinities with South American clades than with representative northern African form, suggesting that tectonically driven separation of the two landmasses may have influenced the development of progressively isolated southern African faunas throughout the Cretaceous.

ACKNOWLEDGMENTS

We thank D. Kamamba, E. Maro, A. Tibiajuka, J. Temu, and the late J. Temba (Tanzania Antiquities Unit), C. Mtelela, E. Mshui, and N. Boniface (University of Dar es Salaam), and the Tanzania Commission for Science and Technology (COSTECH) for logistical and administrative support; J. P. Cavigelli for assistance with mechanical preparation; members of the 2002–2004 Rukwa Rift Basin Project expeditions for field assistance; H. and M. Faessler for continued support in Tanzania; E. Gomani for specimen access in the collections at the Malawi Division of Antiquities in Lilongwe and Blantyre, Malawi; M. Lamanna provided photographs used for comparative purposes and discussions; M. D'Emic and P. Mannion for fruitful discussions; and B. Keaner, C. Pugh, and J. Sands (Holzer Clinic, Athens, Ohio) for assistance with computed tomography scanning. P. A. Gallina and A. Martinelli provided useful reviews and suggestions on the original submission of this contribution. This research was supported by the U.S. National Science Foundation (NSF EAR_0617561, EAR_0933619, EAR_1349825), the National Geographic Society (CRE), the Ohio University Heritage College of Osteopathic Medicine, Ohio University Office of Research and Sponsored Programs, Ohio University African Studies Program, Ohio University Student Enhancement Award and Original Work Grant (E.G.), the Jurassic Foundation (E.G.), and the Paleontological Society (E.G.).