Deinonychosaur Trackways in Southeastern China Record a Possible Giant Troodontid

The Longxiang tracksite (lower Upper Cretaceous, Shanghang Basin) includes twelve didactyl deinonychosaur tracks that fall into two morphologies, differentiated by both size and form. The smaller tracks (∼11 cm long) are referable to the ichnogenus . The larger tracks (∼36 cm long) establish the ichnotaxon . Based on the size of the tracks, has an estimated hip height of over 1.8 m, a size comparable to that of the largest known deinonychosaurs, i.e., and . The reduced form of digit IV, relative to digit III, indicates that is a probable troodontid. Gigantism evidently evolved independently at least four times within the Deinonychosauria and within at least three major lineages: the Eudromaeosauria, Unenlagiidae, and Troodontidae. In the mid-Cretaceous of Asia, the evolution of overlapped with that of early large-bodied tyrannosauroids and with previously established large allosaurids (although the latter may have been in decline).