Wide-gauge sauropod trackways from the Early Jurassic of Sichuan, China: oldest sauropod trackways from Asia with special emphasis on a specimen showing a narrow turn

Abstract

An Early Jurassic sauropod dinosaur tracksite in the Lower Jurassic Zhenzhuchong Formation at the Changhebian site in Dazu County, Sichuan, is known to have yielded the trackway of a turning sauropod. A re-study of the site shows that all in all there are more than 100 tracks organized in at least three sauropod trackways. The narrow turn in one of the trackways is confirmed and analyzed in greater detail. All of the trackways show a wide gauge similar to Brontopodus-type trackways, but simultaneously exhibit high heteropody typical for Parabrontopodus-type trackways. The relative length of pes digits I, II and III is difficult to determine, but is suggestive of a primitive condition where digit I is less well developed than in Brontopodus. Thus far, they are the stratigraphically oldest sauropod trackways known from Asia being Hettangian in age. Previously, the trackway with the narrow turn was reported as the first turning sauropod trackway from Asia, but recently several other turning trackways have been reported suggesting that this behaviour is more commonly found than previously assumed and is now documented from the Early Jurassic to Late Cretaceous. Most of these examples show tight turns of between ~90° and as much as 180° suggesting that despite their large size sauropods could quite easily and abruptly change their direction of movement.