An unusual sauropod turning trackway from the Early Cretaceous of Shandong Province, China

An unusual turning and a regular, straight sauropod trackway both left by small trackmakers, as well as additional isolated medium-sized to large sauropod tracks are described from the Early Cretaceous Dasheng Group of the Zhucheng Basin, Shandong Province, China. Based mainly on well-preserved tracks exhibiting three forwardly-directed digit/claw impressions and a pronounced heteropody, and to a lesser degree due to a predominantly narrow to medium trackway gauge, the two small trackways are assigned to the Parabrontopodus ichnotaxon. As there is no clear trackway and no well-preserved tracks amongst the medium-sized to large sauropod tracks, these tracks can only be identified as of sauropod origin but they cannot be assigned to an ichnotaxon. The unusual turning trackway is characterized by a highly variable trackway configuration (pes and manus outward rotation, gauge, pace, stride) and pattern (different degree of manus overprinting by pes tracks) along its course, evidently related to the narrow, semicircular turn to the left that the animal made. This is also associated with a pronounced change from a narrow-medium (in the straight part at the beginning) to a (very) wide (within the turn) gauge. This demonstrates that these two stances could have been used by one and the same sauropod trackmaker, even if in the present case associated with turning and not simply during straight progression, as it was already reported from a Late Jurassic tracksite from NW Switzerland and an Early Cretaceous tracksite from Spain. Such 'untypical' trackways provide important constraints for the reconstruction of locomotor characteristics of sauropods such as unsteady locomotion and changes in locomotor behavior, and they will be of particular interest in the future to model and understand the different 'locomotor styles/capabilities' sauropods were engaged in.