Theropod and turtle tracks from the Middle Jurassic Zhiluo Formation in Shaanxi, China: implications for a newly defined <i>Chelonipus</i> ichnocoenosis

An assemblage of eubrontid-type theropod tracks, representing terrestrial progression and turtle track swim tracks representing subaqueous progression characterises a newly reported site in the Middle Jurassic Zhiluo Formation in Shaanxi Province China. While eubrontid tracks are common in the Jurassic of China, turtle swim tracks have only comparatively recently been reported from the Mesozoic of China, and the present report appears to represent the oldest occurrence of the latter. The co-occurrence of theropod tracks and turtle swim tracks suggests alternating registration of tracks on emergent and subaqueous substrates as localised water-levels fluctuated. The co-occurrence can be characterised as the intersection of an eubrontid ichnocoenosis with a newly defined Chelonipus ichnocoenosis