A new deinonychosaurian track from the Lower Cretaceous Hekou Group, Gansu Province, China

摘要

Herein we describe deinonychosaurian (Dinosauria: Theropoda) tracks in the Lower Cretaceous Hekou Group at sites I and II of Liujiaxia Dinosaur National Geopark, Gansu Province, China. The site preserves 71 didactyl tracks, the largest concentration of deinonychosaurian tracks in Asia. The tracks pertain to a new dromaeopodid ichnospecies: Dromaeo? sauripus yongjingensis ichnosp. nov., which is diagnosed by: a digital pad formula of x?1?3?4?x and a mean divarication angle between digits III and IV of 19°, and having the proximal portion of digit II contacting the anterior margin of a large, rounded metatarsophalangeal pad. Six Dromaeosauripus trackways from site II comprise at least two, and possibly three, turning trackways in which the track maker(s) turned without slowing down. None of the Dromaeosauripus trackways are parallel or closely spaced, suggesting that they were made by solitary track makers. Estimates of dromaeopodid track?maker sizes are between 61–300 cm, well within the size range established by body fossils of both dromaeosaurids and troodontids.