Late Cretaceous ornithopod-dominated, theropod, and pterosaur track assemblages from the Nanxiong Basin, China: New discoveries, ichnotaxonomy, and paleoecology

Re-examination of the Late Cretaceous Yangmeikeng tracksite, in the Zhutian Formation (Nanxiong Group) near Nanxiong, Guangdong Province, China, has led to the documentation of over 30 vertebrate tracks. The track assemblage is dominated by large and small ornithopod tracks. The larger ornithopod tracks have been assigned to Hadrosauropodus nanxiongensis and Hadrosauropodus isp. indet. The smaller ornithopod tracks are consistently incomplete, showing only three pes digit traces, without heel or manus impressions. For this reason the smaller tracks probably represent pes tracks penetrating from a higher layer, and therefore have not been assigned to any particular ichnotaxon. Previous photography at Yangmeikeng site confirms the presence of at least one small Wupus-like theropod track and a Pteraichnus-like pterosaur pes track. Large enigmatic didactyl tracks could be of deinonychosaurian affinity, but are more likely the poorly preserved prints of a tridactyl theropod trackmaker. The Nanxiong dinosaur tracks and skeleton records represent the most important and diverse ichnofauna from Upper Cretaceous strata of South China, and can be compared with the Shandong and Heilongjiang Late Cretaceous faunas. The composition of the ichnofauna, is significant because it reflects a diverse tetrapod community with hadrosaurs, avian theropods, non-avian theropods and pterosaurs, a co-occurrence not evident from the skeletal record of this region. From a global perspective this assemblage permits a unique insight into archosaur communities and interaction of animals in a typical Late Cretaceous lakeshore environment. Non-avian theropods may have been attracted by the other groups that were considered as a potential prey.