Triassic-Jurassic dinosaurs from India, their ages and palaeobiogeographic significance

Abstract

ABSTRACT We review the record of Late Triassic and Jurassic dinosaurs from India to determine their geological ages and palaeobiogeographic significance. The oldest Indian dinosaur, the basal saurischian Alwalkeria maleriensis, is from the early Late Triassic (Otischalkian/Carnian) lower Maleri Formation. The archosaur-dominated Upper Maleri Formation (Adamanian/late Carnian?) contains two sauropodomorph clades. The Indian Jurassic record of dinosaurs from the Pranhita-Godavari Valley is more extensive but has poor age constraints, whereas fragmentary, and better dated dinosaur remains are known from the Early Middle Jurassic of Kachchh, Gujarat and Rajasthan. The Indian Late Triassic dinosaurs fit into a picture of some degree of dinosaur cosmopolitanism across Late Triassic Pangaea, with primitive saurischians and/or theropods and primitive sauropodomorphs found in eastern Gondwana (India), western Gondwana (South America) and Euramerica. The well-known non-neosauropods Kotasaurus and Barapasaurus from the Middle Jurassic Kota Formation provide substantial evidence that India was a major centre of the early evolution of neosauropods. Tharosaurus indicus, from the Middle Jurassic strata of the Jaisalmer Basin, is a relic of a lineage that likely originated in India and swiftly expanded throughout the rest of Pangaea. This lineage further stresses the significance of Gondwanan India in elucidating the origin and early evolutionary history of neosauropod dinosaurs.