Theropod tracks from the Lower Jurassic of Gulin area, Sichuan Province, China

The Jiaoyuan tracksite in the Gulin area of Sichuan Province, China represents a typical saurischian-dominated assemblage with trackways of theropods and sauropods. They occur in the Lower Jurassic Da'anzhai Member of the Ziliujing Formation, a sandstone-siltstone succession of fluvial origin and deposited in the southern Sichuan Basin. Four trackways as well as isolated tracks of theropods are documented and analyzed in this first part a study of sauropod tracks will follow elsewhere. Two morphotypes and size-classes, respectively, can be observed. The larger one is 25-34 cm in length and shows weak to moderate mesaxony. The smaller is 7-15 cm in length and moderately mesaxonic. Despite a few similarities with the ichnogenus Kayentapus, the former is assigned here to Eubrontes, well known from Lower Jurassic assemblages, in North America, Europe, and southern Africa. The smaller morphotype resembles typical Grallator tracks except in its wider digit divarication and the metatarsophalangeal pad IV being positioned in line with the long-axis of digit III, similar to Jialingpus described, for example, from Upper Jurassic deposits of Sichuan. A relatively wide digit divarication in Grallator-type tracks is apparently common in Jurassic assemblages of China and may represent a distinct feature related to provinciality of theropod faunas in this region.