Titanosauria (Dinosauria, Sauropoda) from the Upper Cretaceous (Turonian) Bissekty Formation of Uzbekistan

ABSTRACT

Exposures of the Bissekty Formation (Upper Cretaceous: middle–upper Turonian) at Dzharakuduk in the central Kyzylkum Desert of Uzbekistan have yielded abundant dinosaurian remains. We report here on cranial and postcranial remains that can be attributed to titanosaurian sauropods. This material is of considerable interest in view of the relative scarcity of sauropod fossils from the Upper Cretaceous of Central Asia. An incomplete braincase originally assigned to the ceratopsian Turanoceratops tardabilis actually belongs to a derived titanosaurian. It shares a number of features (including broad basal tubera and presence of wide depression between basal tubera) with braincases of various derived titanosaurian taxa from Asia and South America. Computed tomographic (CT) scanning of the braincase permitted digital reconstruction of a partial endocast. Overall, this endocast resembles those of other sauropods, although the pituitary fossa is considerably swollen. As in other derived titanosaurians, the abducens nerve passed lateral to the pituitary fossa. The inner ear resembles that of some other titanosaurs in having a very short lateral semicircular canal and that the anterior semicircular canal is only slightly longer than the posterior one. Isolated sauropod teeth from Dzharakuduk have slender, ‘pencil-shaped’ crowns, which often bear high-angle apical wear facets. The caudal vertebrae are gently opisthocoelous rather than procoelous, as is typically the condition on at least the anterior caudals in many other titanosaurs. An anterior caudal vertebra shows extensive pneumatization of its neural arch. The sauropod remains from the Bissekty Formation establish the presence of titanosaurians in Central Asia during the Turonian.

ACKNOWLEDGMENTS

H.-D.S. and A.A. thank A. V. Abramov, J. D. Archibald, G. O. Cherepanov, I. G. Danilov, S. Dominguez, C. King, N. Morris, C. M. Redman, A. S. Resvyi, C. Skrabec, P. P. Skutschas, E. V. Syromyatnikova, and D. J. Ward for their efforts in the field, scientific expertise, and camaraderie. The cooperation of the Zoological Institute of the National Academy of Sciences of Uzbekistan is greatly appreciated. I. Morrison carefully prepared USNM 538127. For assistance with CT scanning of CCMGE 628/12457, we thank H. Rockhold, RT, and O’Bleness Memorial Hospital, Athens, Ohio. We are indebted to M. D. D’Emic (Stony Brook University) and A. Paulina Carabajal (Museo Carmen Funes) for constructive reviews of a draft of the manuscript. H.-D.S. and A.A. gratefully acknowledge financial support from the National Science Foundation (EAR-9804771 and EAR-0207004 to J. D. Archibald and H.-D. Sues), the National Geographic Society (5901-97 and 6281-98 to J. D. Archibald and H.-D. Sues), the Navoi Mining and Metallurgy Combinat, the Civilian Research and Development Foundation (RU-G1-2571-ST-04 and RUB1-2860-ST-07), the Russian Fund of Basic Research (07-04-91110-AFGIRa) and the Russian Scientific Fund project 14-14-0015. L.M.W. and R.C.R. acknowledge support from the Ohio University Heritage College of Osteopathic Medicine and the National Science Foundation (IBN-0343744, IOB-0517257, IOS-1050154). The Ohio Supercomputing Center provided additional support.