A diversified vertebrate ichnite fauna from the Feitianshan Formation (Lower Cretaceous) of southwestern Sichuan, China

Abstract

The Bajiu tracksite exposed on a fine sandstone surface at the top of the Feitianshan Formation, close the contact with the overlying Xiaoba Formation, reveals a saurischian dominated ichnofauna consisting of four sauropod and at least eight theropod trackways. The sauropod trackways display a medium-wide gauge pattern characteristic of titanosauriforms, while the theropod trackways can be subdivided into two distinct morphotypes. One is similar to the ichnogenera Eubrontes and Megalosauripus, the other (cf. Dromaeopodus) appears to represent a functionally didactyl dromaeosaur where pedal digit II is represented only by an oval basal pad. A single swim track is possibly attributable to a turtle or crocodylian. Such sauropod-theropod dominated ichnofaunas are consistently typical of the red-bed tracksites in the region and useful for characterizing a fauna that is otherwise poorly known from body fossils. The stratigraphic position and late occurrence of the (typical Jurassic) Eubrontes-Megalosauripus morphotype is well known from other Cretaceous localities in China and seems to reflect a peculiarity in the theropod faunas of East Asia.