Osteology of the sauropodomorph dinosaur Jaklapallisaurus asymmetricus from the Late Triassic of central India.

Abstract

The Gondwana formations exposed in the Pranhita-Godavari Valley of central India include Middle Triassic to Lower Jurassic continental deposits that provide essential information about the tetrapod assemblages of that time, documenting some of the oldest known dinosaurs and the first faunas numerically dominated by this group. The Upper Maleri Formation of the Pranhita-Godavari Basin preserves an early-middle Norian dinosaur assemblage that provides information about the early evolutionary history of this group in central-south Gondwana. This assemblage comprises sauropodomorph dinosaurs and an herrerasaurian, including two nominal species. Here, we describe in detail the anatomy of one of those early dinosaurs, the bagualosaurian sauropodomorph Jaklapallisaurus asymmetricus. The new anatomical information is used to investigate the position of the species in an updated quantitative phylogenetic analysis focused on early sauropodomorphs. The analysis recovered Jaklapallisaurus asymmetricus as a member of Unaysauridae, at the base of Plateosauria, together with Macrocollum itaquii and Unaysaurus tolentinoi from the early Norian of southern Brazil. This phylogenetic result indicates that the dispersal of early plateosaurian sauropodomorphs between the Southern Hemisphere and what nowadays is Europe would have occurred shortly after Ischigualastian times because of the extension of their ghost lineage. Thus, the presence of early plateosaurians in the early Norian of South America and India reduces a previously inferred diachrony between the biogeographic dispersals of theropods and sauropodomorphs during post-Ischigualastian times.