Shuangbaisaurus in Yunnan
Shuangbaisaurus (meaning “Shuangbai reptile”安龙堡双柏龙 in Chinese) is an extinct genus of theropod dinosaur, possibly a dilophosaurid, that lived in the Early Jurassic of Yunnan Province, China. It contains a single species, S. anlongbaoensis, represented by a partial skull. Like the theropods Dilophosaurus and Sinosaurus, the latter of which was its contemporary, Shuangbaisaurus bore a pair of thin, midline crests on its skull. Unusually, these crests extended backwards over the level of the eyes, which, along with the unusual orientation of the jugal bone, led the describers to name it as a new genus. However, Shuangbaisaurus also possesses a groove between its premaxilla and maxilla, a characteristic which has been used to characterize Sinosaurus as a genus. Among the two morphotypespresent within the genus Sinosaurus, Shuangbaisaurus more closely resembles the morphotype that is variably treated as a distinct species, S. sinensis, in its relatively tall skull.
Discovery and Location:
Shuangbaisaurus is known from Yunnan Province, China, specifically from the Early Jurassic Fengjiahe Formation, dating approximately to the Hettangian stage, about 190-180 million years ago.
Description:
- Shuangbaisaurus had a robust skull measuring about 54 cm in length, with a distinctive length-to-height ratio and thin, elongated crests extending backwards over its eye sockets. These crests were primarily formed by the frontal bone and possibly the postorbital and prefrontal bones.
- Similar to Dilophosaurus and some morphotypes of Sinosaurus, Shuangbaisaurus had a groove between its premaxilla and maxilla, distinguishing it from other theropods.
- The antorbital fenestra was large, occupying a significant portion of the skull length, and the orbit was keyhole-shaped, distinguishing it from related species like Sinosaurus.
Naming and Classification:
- The genus name Shuangbaisaurus refers to Shuangbai County, where it was discovered, and the species name anlongbaoensis refers to Anlongbao Town, the locality of the fossil find.
- It is classified as a basal tetanuran theropod, possibly related to dilophosaurids like Dilophosaurus and certain morphs of Sinosaurus.
Paleoecology:
- Shuangbaisaurus coexisted with a diverse fauna in the Fengjiahe Formation, including sauropodomorphs like Yunnanosaurus and Lufengosaurus, along with diverse ichnofauna and other vertebrates and invertebrates typical of Early Jurassic ecosystems.
Significance:
- Shuangbaisaurus contributes to our understanding of early theropod evolution in Asia and adds to the diversity of dinosaurs known from Yunnan Province.
