A Sauropod Braincase from the Pab Formation (Upper Cretaceous, Maastrichtian) of Balochistan, Pakistan

Abstract

Recent geological and paleontological exploration in the Pab Formation (Upper Cretaceous) of Balochistan Province has uncovered new terrestrial vertebrate remains. Together with Cretaceous vertebrates from India, the Pab vertebrates provide information about the paleobiogeographic history of Indo-Pakistan during its northward migration towards Asia. Vertebrate remains collected from several localities in the Pab Formation include numerous, isolated postcranial bones attributable to titanosaur sauropods and a well-preserved sauropod braincase that is described here. The Pab braincase is referable to Eusauropoda, but it does not preserve characteristics diagnostic of lowerlevel sauropod clades. The Pab braincase is relatively small and diagnosed by a prominent supraoccipital wedge, pronounced proatlantal facets, and a ventrally deflected occipital condyle that forms a 120° angle with the skull roof. Sauropod braincase material collected from Lameta Formation localities in India (Bara Simla, Dongargaon) closely resembles the Pab braincase in size and general morphology and shares one or more of its diagnostic features. The Indian and Pakistani braincases likely represent the same genus or species, which was distributed across Indo-Pakistan during the Cretaceous. Further exploration in both countries will better constrain the distribution of these and other vertebrate fossils, providing a clearer picture of the Cretaceous vertebrate fauna of Indo-Pakistan.