The non-avian theropod track Jialingpus from the Cretaceous of the Ordos Basin, China, with a revision of the type material: Implications for ichnotaxonomy and trackmaker morphology

Abstract

Deposits from the Ordos Basin of mid-western China are rich in body fossils and ichnofossils of Early Cretaceous vertebrates. Thousands of Early Cretaceous sauropod, theropod and bird tracks described since 1958 have been found at several localities in the basin. We report two new sites (Dijiaping and Bawangzhuang) in the Luohe Formation of the Ordos Basin, Shaanxi Province, which contain small theropod footprints that are here referred to the ichnogenus Jialingpus. The assignment is based on pad configurations including (1) the large metatarsophalangeal area positioned in line with the axis of digit III, (2) the subdivision of this part into a small pad behind digit II, which in some specimens is close to the general position of the hallux (digit I), and a large metatarsophalangeal pad behind digit IV, and (3) a distinct inter-pad space between metatarsophalangeal pads and proximal phalangeal pads of digits II and III. We re-describe the type material of the type ichnospecies Jialingpus yuechiensis from the Upper Jurassic Penglaizhen Formation of Sichuan Province, proposing a largely amended diagnosis for this ichnotaxon. The presence of a digit I trace in the holotype, indicating a relatively long hallux, and the large metatarsophalangeal area positioned in line with digit III distinguishes Jialingpus from the ichnogenus Grallator and similar tracks that all lack these features. The only difference between Jialingpus specimens from the Cretaceous of the Ordos Basin and those of the Jurassic Penglaizhen Formation is the larger digit divarication in the Cretaceous taxon. This is the fourth record of Jialingpus in China and the second in Cretaceous strata, with the first being those from the Huangyangquan locality in Xinjiang, China.