Sinosaurus (meaning "Chinese lizard") is an extinct genus of basal theropod dinosaur which lived during the Early Jurassic (Hettangian-Sinemurian).

In 2003, Dong Zhiming studied the material of Sinosaurus triassicus, finding it to be quite similar to Dilophosaurus sinensis.

[12] A complete skull with a preserved mandible and 11 cervical vertebrae was described for Sinosaurus in 2023, after it was discovered near the locality where the holotype was found.

With the use of virtual skeletal mount, Liang et al. (2024) estimated that Sinosaurus was a large theropod around 5.85 metres (19.2 ft) long with a maximum body mass of 895 kilograms (1,973 lb).

The authors suggested that since the phylogenetic position of Sinosaurus is not well understood, previous estimations based on extant scaling approaches derived from femur length and circumference are unreliable.

The most distinctive feature is a pair of large crests over the antorbital fenestra, formed from the nasal and lacrimal bones, which superficially resemble those of Dilophosaurus.

[11] Eight major fenestrae are littered throughout the skull, including the nasal cavity (nostril) and the orbit (eye socket).

[1] It is possibly closer to the Antarctic theropod Cryolophosaurus, based on the fact that the anterior end of the jugal does not participate in the internal antorbital fenestra and that the maxillary tooth row is completely in front of the eye socket.

[21] Although the skull of D. sinensis sports large nasolacrimal crests superficially like those reconstructed in D. wetherilli, features elsewhere in the skeleton suggest it is closer to tetanuran theropods.

Phylogenetic analysis of this specimen, demonstrates that Sinosaurus is a more derived theropod, and is not the most basal dilophosaurid, as held by Smith et al.[2] A cladogram was identified by Christophe Hendrickx and Octávio Mateus.

[23] Eoraptor Herrerasaurus Dilophosaurus Coelophysis bauri Coelophysis rhodesiensis Elaphrosaurus Ceratosaurus Majungasaurus Masiakasaurus Cryolophosaurus Sinosaurus Chuandongocoelurus Monolophosaurus Megalosauroidea Avetheropoda Recent studies placed Sinosaurus outside the Ceratosauria+Tetanurae clade,[24][25][26] while Wang et al. (2016) considered it the basalmost ceratosaur.

Dong (2003) proposed that the notch was used to house jaw muscles, giving Sinosaurus a powerful bite.

Dong suspected that the premaxilla was covered in a narrow, hooked beak, that was used to rip open skin and abdominal flesh.

[2] The authors concluded that this finding "contributes to mounting evidence suggesting theropods were highly resilient to a broad spectrum of traumas and diseases.

[11] The type specimen of Sinosaurus triassicus IVPP V34 was recovered in the Zhangjiawa Member of the Lufeng Formation, in Yunnan, China.

These remains were discovered at the Dark Red Beds that were deposited during the Sinemurian stage of the Jurassic period, approximately 196-183 million years ago.

[32] Specimen IVPP V504, referred to Sinosaurus, a maxilla with four teeth, was collected by Lee in the 1940s, in the Dull Purplish Beds of Shawan Member of the Lufeng Formation, that were deposited during the Hettangian stage of the Jurassic period, approximately 201-199 million years ago.

[29] The D. sinensis remains, KMV 8701, a nearly complete skeleton, now referred to Sinosaurus, were recovered in the Shawan Member of Lufeng Formation.

This material was discovered in 1987 in the Dull Purplish Beds that were deposited during the Hettangian stage of the Early Jurassic, approximately 201-199 million years ago.

[34] Contemporary dinosaurs include indeterminate sauropods; the early thyreophorans Bienosaurus lufengensis and Tatisaurus oehleri; the supposed chimeric ornithopod "Dianchungosaurus lufengensis"; the prosauropods Gyposaurus sinensis, Lufengosaurus huenei, L. magnus, Jingshanosaurus xinwaiensis,[34] Kunmingosaurus wudingensis, Chinshakiangosaurus chunghoensis, Yunnanosaurus huangi, "Y."