Newly discovered tracksites from Middle Jurassic Chaya Group of Eastern Tibet, China, with the implications of saurischian distribution in around the eastern Tethys

Northeastern Tibet is one of the most important regions of the Early to Middle Jurassic dinosaur fauna in the eastern Tethys, yielding abundant skeletal and track records of brachiosaurid and cetiosaurid sauropods, coelurosaurid theropods, scelidosaurid and stegosaurid ornithischians, etc. The new discovery of two dinosaur track sites from the Middle Jurassic Dongdaqiao Formation, situated in Dongduo Village of Changdu City, Eastern Tibet, China is reported. The dinosaur tracks are co-occur with the Scoyenia ichnofacies that linked to shallow, freshwater environmrnt. The track assemblages encompass a trackway contains three consecutive large-sized theropod footprints which are consistent with the morphofamily Eubrontidae, along with isolated and tiny sauropod tracks provisionally classified as cf. Parabrontopodus isp. These sauropod tracks are notable for their tiny size, with the pes tracks ranging from 8.8 cm to 15.5 cm, comparable to the smallest sauropod tracks ever recorded in the world, and the trackmaker was probably about two to three metres long. All the new data further strengthen the previous hypothesis that southwest China, part of the eastern Tethys region, were dominated by saurischia in the Middle Jurassic.