Tharosaurus

Tharosaurus (meaning "Thar Desert lizard") is an extinct genus of dicraeosaurid sauropod dinosaur from the Middle Jurassic Jaisalmer Formation of India. The genus contains a single species, T. indicus, known from several vertebrae and a rib. Tharosaurus represents the earliest diplodocoid currently known and the first described from India.^[1]

Tharosaurus Temporal range: Middle Jurassic, 168.3–166.1 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Cervical vertebrae of the holotype
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	†Sauropodomorpha
Clade:	†Sauropoda
Superfamily:	†Diplodocoidea
Family:	†Dicraeosauridae
Genus:	†Tharosaurus Bajpai et al., 2023
Species:	†T. indicus
Binomial name
†Tharosaurus indicus Bajpai et al., 2023

Discovery and naming

Speculative life restoration

The Tharosaurus holotype specimen, RWR-241 (A–K), was discovered between 2019 and 2021 in sediments of the Jaisalmer Formation near Jethwai village in Jaisalmer district of Rajasthan state in western India.^[2] The specimen consists of partial cervical, dorsal, and caudal vertebrae and a dorsal rib.^[1]

Tharosaurus type locality in Jaisalmer Formation near Jethwai village, Jaisalmer district, Rajasthan, India

In 2023, Bajpai et al. described Tharosaurus indicus as a new genus and species of dicraeosaurid sauropod based on these fossil remains. The generic name, "Tharosaurus", combines a reference to the Thar Desert where the holotype was found with the Greek word "sauros", meaning "lizard". The specific name, "indicus", refers to the discovery of the specimen in India.^[1]

Classification

Bajpai et al. (2023) recovered Tharosaurus as an early-diverging dicraeosaurid, suggesting it represents a relic of a lineage that evolved in India and later spread across the world. Tharosaurus is the oldest dicraeosaurid, as well as the oldest diplodocoid. The results of their phylogenetic analyses are shown in the cladogram below:^[1]

Diplodocoidea	Rebbachisauridae Flagellicaudata Diplodocidae Dicraeosauridae Suuwassea Lingwulong Bajadasaurus Tharosaurus Pilmatueia Amargatitanis Brachytrachelopan Dicraeosaurus hansemanni Amargasaurus

Paleoenvironment

The Jaisalmer Formation represents a deposit on the Tethyan coast of India. Other dinosaurs from this environment include a large theropod and a turiasaurian sauropod both known only from teeth,^[3][4] along with a possible spinosaurid known only from a toe claw.^[5]