STEGOSAUR TRACK ASSEMBLAGE FROM XINJIANG, CHINA, FEATURING THE SMALLEST KNOWN STEGOSAUR RECORD

Abstract

ABSTRACT Tracks attributable to small ornithischian dinosaurs (thyreophorans and cerapodans) are generally rare in comparison with those representing large individuals. Here we report a presumed stegosaur track (ichnogenus Deltapodus) only 5.7 cm long originating from the Lower Cretaceous Tugulu Group of Xinjiang Province, China, co-occurring with the tracks of larger individuals. This track is only 15% as long as the type of Deltapodus curriei from the same locality. This is the smallest convincing example of a Deltapodus currently known. Reports of purported diminutive stegosaur tracks from the Jurassic of North America have been refuted. A review of well-known ornithischian track ichnogenera reveals that small tracks, less than 11.0–12.0 cm are rare, with only one previous report of a Deltapodus only 8.0 cm long. Most other reported tracks of these ichnogenera represent large individuals with footprint lengths mostly in the range of 30–50 cm. The scarcity of small ornithischian tracks contrasts with the relative abundance of small theropod tracks. The reasons for this paucity of small ornithischian tracks may be due to paleobiological (ontogenetic or paleoecological) or non-paleobiological (preservational) factors.