First report of turtle and sauropod track assemblages from the Early Jurassic of Guizhou, China

The Guizhou Province possesses a relatively limited number of tetrapod skeletal records from the Jurassic and Cretaceous periods in comparison to its renowned marine reptile fauna from the Triassic. In light of this, the discovery of track fossils represents a significant advance in the understanding of the Mesozoic fauna of the region. In contrast with previous findings of Mesozoic tracks belonging to marine reptiles, pseudosuchians and dinosaurs, this study presents the first documented occurrence of turtle tracks (cf. Chelonipus) from this region, discovered in the Ziliujing Formation of the Yaocun tracksite. The tracks are preserved on a microbial mat on the surface of reddish mudstone and are morphologically distinct from the mostly elongate tracks characterized by scratches previously found in China. This suggests that the site represents a comparatively shallow bathymetry. In addition, the presence of associated sauropod (or basal sauropodomorph) tracks on the same surface, an ichno-assemblage hitherto unknown from any other tracksites, extends the temporal range of the Chelonipus ichnocoenosis to Early Jurassic, and furthermore adds sauropodomorphs to this latter community. It enhances the faunal biodiversity of Mesozoic riparian shallow-water ecosystems on relatively short time scales, and provides further insights into the environmental constraints that define this faunal assemblage.