Taxonomical revision of fossil Canis in Middle Pleistocene sites of Zhoukoudian, Beijing, China and a review of fossil records of Canis mosbachensis variabilis in China

Canis mosbachensis is a widely distributed species from the Early to Middle Pleistocene in Europe. In Eastern Asia, Canis variabilis was supposed to be a local subspecies of C. mosbachensis, but such hypothesis has never been tested in details. Here we restudied the Canis materials from type locality, Loc.1 of ZKD (Zhoukoudian) of Middle Pleistocene, as well as other localities that produced important materials of this taxon (e.g. Loc.13 of ZKD). To better evaluate the variability of the Pleistocene Canis, a series of morphotypes are described. Based on morphotype and morphometric, the present study reveals there is only one species present at Loc.1 and Loc.13 of ZKD, which is quite similar to European C. mosbachensis and should be revised as a subspecies of C. mosbachensis, namely C. mosbachensis variabilis. C. m. variabilis is more derived and less hypercarnivorous than the Early Pleistocene Canis chihliensis (as well as European Canis etruscus and Canis arnensis) in craniodental characters, whereas it is less derived and less hypercarnivorous than Canis lupus. A review of fossil records of C. m. variabilis in China was made based on these different characters. Canids from Gongwangling, Lantian of Shaanxi Province (middle or late Early Pleistocene) are the earliest known representatives of C. mosbachensis in China, which are still more primitive than C. m. variabilis from the Middle Pleistocene sites of ZKD. Reliable records of C. mosbachensis are only known from the Early Pleistocene to the late Middle Pleistocene in Northern China. C. m. variabilis is not direct ancestor to C. lupus but a close relative of the latter, while it is far from the Early Pleistocene C. chihliensis. The latter remains more primitive characters that are more similar to those of European Canis etruscus and Canis arnensis.