Tharosaurus

MEANING: Thar Desert lizard

PERIOD: Middle Jurassic

CONTINENT: Asia

Tharosaurus is an early-diverging dicraeosaurid sauropod, and the earliest diplodocoid currently known. Dicraeosaurids are advanced sauropods characterized by relatively small body size, short necks, and long neural spines. They were herbivorous and primarily browsed close to the ground or at mid-height, due to the shape of their necks and skulls.

Abstract from paper: The Early Jurassic and Cretaceous deposits of India are known for their diverse sauropod fauna, while little is known from the Middle and Late Jurassic. Here we report the first ever remains of a dicraeosaurid sauropod from India, Tharosaurus indicus gen. et sp. nov., from the Middle Jurassic (early–middle Bathonian) strata of Jaisalmer Basin, western India. Known from elements of the axial skeleton, the new taxon is phylogenetically among the earlier-diverging dicraeosaurids, and its stratigraphic age makes it the earliest known diplodocoid globally. Palaeobiogeographic considerations of Tharosaurus, seen in conjunction with the other Indian Jurassic sauropods, suggest that the new Indian taxon is a relic of a lineage that originated in India and underwent rapid dispersal across the rest of Pangaea. Here we emphasize the importance of Gondwanan India in tracing the origin and early evolutionary history of neosauropod dinosaurs.

Tharosaurus is from the Middle Jurassic. The Middle Jurassic, spanning from approximately 174 to 163 million years ago, was a period of increasing tectonic activity and evolutionary innovation. By this time, the supercontinent Pangaea had begun to split more significantly, with Laurasia in the north and Gondwana in the south drifting apart. This movement created new coastlines, shallow seas, and rift valleys that fostered diverse ecosystems. The climate remained generally warm and humid, promoting the spread of lush vegetation, including ferns, cycads, and conifers, which blanketed much of the land and supported a wide variety of herbivorous dinosaurs.

Though less well known than the Late Jurassic, the Middle Jurassic was an important evolutionary chapter. Several major dinosaur groups began to diversify, including the stegosaurs and more derived long-necked sauropods that would later dominate the landscape. Theropods also continued to evolve, giving rise to new lineages like the megalosaurids and the early ancestors of more derived carnivores. Fossil evidence from this interval is relatively scarce compared to later stages, but what we do have paints a picture of an increasingly complex world, setting the stage for the iconic ecosystems of the Late Jurassic.

Tharosaurus is a dicraeosaur. Dicraeosauridae was a group of sauropod dinosaurs known for their relatively short necks, tall neural spines, and more compact body plans compared to their longer-necked relatives. They lived primarily during the Late Jurassic and Early Cretaceous and are part of the larger diplodocoid lineage, though they are quite distinct from the more elongated forms that group is famous for. Instead of long, sweeping necks used to browse high vegetation, dicraeosaurs had stiff necks supported by tall vertebral spines, which may have helped them feed closer to the ground or at mid-level heights.

Members of this group are sometimes known for their elongated, paired spines running down their necks. These may have supported a sail or been used for display or defense. Dicraeosaurids are mainly known from Gondwana, suggesting they had a southern hemisphere distribution during a time when continental drift was breaking apart Pangea. Their smaller size and unique feeding strategies hint at ecological niches different from those of their more massive, high-browsing cousins, showing just how diverse and adaptable sauropods could be.