Titanosauria is the final and most diverse radiation of sauropod dinosaurs, which is predominantly distributed throughout the Late Cretaceous of Gondwana. Previous hypotheses have suggested that Gondwana might have served as the origin for Titanosauria. However, the presence of a significant number of titanosaurs with procoelous caudal vertebrae in the Early Cretaceous of Asia indicates that the titanosaurian bauplan may have been established on the northern continents as early as the earliest Cretaceous. In contrast, the titanosaurs with procoelous both anterior and middle caudal vertebrae appeared in South America only during the Albian. The most recent research has identified the Tengrisaurus starkovi Averianov et Skutschas, 2017 from the Lower Cretaceous (Valanginian) Murtoi Formation at the Mogoito locality in Buryatia, Transbaikalia, Russia, as the earliest documented sauropod to display the titanosaurian bauplan, as evidenced by its procoelous anterior and middle caudal vertebrae. The present study reports on a recently discovered sauropod posterior cervical vertebra from the Mogoito locality, which is attributed to T. starkovi. A novel phylogenetic analysis, incorporating data from the cervical and caudal vertebrae, confirms the position of Tengrisaurus as a basal member of the titanosaurian clade Colossosauria. Consequently, the Valanginian Tengrisaurus is recognized as the earliest member of both Colossosauria and Titanosauria, which substantially supports a potential Asiatic origin of these clades.
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