Dinosaur assemblages from the Middle Jurassic Shaximiao Formation and Chuanjie Formation in the Sichuan-Yunnan Basin, China

Kui LI, Jian LIU, Chunyan YANG, Fang HU

Abstract


The Shaximiao Formation (Sichuan Basin, China), and the corresponding Chuanjie Formation of the neighboring Yunnan Basin (Sichuan-Yunnan Basin), representing continental Mesozoic strata, are distinguished from other Chinese Mesozoic units because of the large area over which they are distributed, their lithological characteristics and their abundant vertebrate fossils. This paper analyses and summarizes the dinosaur fossils from the Shaximiao Formation and compares them to other vertebrate groups of the same or similar ages, both in China and abroad. For the first time, this paper presents the viewpoint that the upper member of the Shaximiao Formation is of Middle Jurassic age (Bathonian–Callovian). Furthermore, we claim that the entire Shaximiao Formation is of Bajocian–Callovian age (middle-late part of Middle Jurassic). This conclusion is supported by the age inferred from invertebrate fossils and radiometric dating (165–178 Ma). The composition, evolution and geological age of the vertebrate fauna (particularly dinosaur fossils), as well as their comparison to the dinosaur fauna from the other parts of the Sichuan-Yunnan Basin (Chuanjie Fm.) is discussed. Middle Jurassic dinosaur assemblages from China show marked differences compared with other dinosaur assemblages in the world, and this is explained by geographical isolation.

Keywords


Dinosaurs; Shaximiao Formation; Chuanjie Formation; Sichuan Basin; Yunnan Basin; Middle Jurassic

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