Fragments of a sauropod species Tharosaurus indicus were discovered in the Thar desert. Credit: Sunil Bajpai
A fossil unearthed from India’s Thar desert offers insights into the evolution of sauropods, the long-necked, plant-eating dinosaurs1.
Scientists at IIT-Roorkee and the Geological Survey of India have found fragments of a sauropod species, Tharosaurus indicus dating to the Middle Jurassic period. The 167-million-year-old partial skeleton is India’s first diplodocoid sauropod find. The fossil’s neck, trunk, and tail fragments predate the sauropod fossil reported from China, by two to three million years.
"This represents the earliest ever record of dicraeosaurs and diplodocoids," says Sunil Bajpai at IIT-Roorkee.
This sauropod group was ubiquitous in the Middle Jurassic to Early Cretaceous (145 million years to 100 million years ago) fauna. The Diplodocus and the Brontosaurus are more popularly known members of this group. Unlike most sauropods, T. indicus was smaller, stretching to around 15 metres, with a shorter neck and tail.
Considering alongside of sauropods, Barapasaurus and Kotasaurus, from central India, and a putative camarasauromorph (sauropod) from Gujarat, T. indicus remnants strongly suggest India was a major centre for diplodocoid dinosaurs and neosauropods. “It all happened here (Gondwanan, India),” says Bajpai.
In the Middle Jurassic period, the Thar desert, where T. indicus roamed, was a forested riverine landscape close to the Tethys Sea. The Indian subcontinent was connected to Madagascar, Africa, and South America in the Gondwana landmass. Gondwana’s northern counterpart, Laurasia, separated by the Tethys seaway, consisted of North America, Greenland, Europe, and northern Asia.
The scientists say the diplodocoids probably moved from India to South America, via Madagascar-Africa, and from there to Laurasia via North America.
If further studies support this analysis, they could shake up the conventional theory, which says diplodocoids evolved in Laurasia and spread elsewhere, says Advait Jukar, a vertebrate paleontologist at University of Arizona in the United States.
The thick sedimentary rock columns of the Jaisalmer basin, formed when Gondwana broke up, turn up unique Jurassic era fossils, including those of sharks. The fossils were dug up north of the Jethwai village between 2019 and 2021 in this basin, a geologically rich landscape of flat plains with low hills fringing the Thar Desert.
New searches in old field areas can yield significant discoveries, says Kristina Curry Rogers, a vertebrate paleontologist at Macalester College in the United States. “Even fragmentary fossils can yield critical pieces that help us answer the puzzle of ancient evolutionary stories,” she said.
