Comparison between woolly rhino forelimbs from Longdan, Northwestern China and Tologoi, Transbaikalian region

The fossil Coelodonta nihowanensis, found from the Late Pliocene loess at Longdan in the Linxia Basin (Gansu, China), is the earliest known member of the woolly rhino. The complete skull from Longdan shows that C. nihowanensis is a primitive species different from Coelodonta antiquitatis. The cranial and dental characters of C. nihowanensis are obviously distinct from those of Coelodonta tologoijensis, and the former has a smaller body size and more slender limb bones. The associate humerus, radius, and ulna, as well as associate carpals and metacarpals of C. nihowanensis found recently from Longdan further show that C. nihowanensis has different postcranial features from C. tologoijensis, and indicate that they belong to two different species. C. nihowanensis is apparently more primitive than C. tologoijensis, and the former has better running ability, which is consistent with the chronological distributions of the two woolly rhino species and the evolutionary trend of the genus Coelodonta. C. nihowanensis may be the ancestral form of C. tologoijensis. The woolly rhino originated in northern China, and then dispersed into northern Eurasia. C. nihowanensis gradually evolved into C. tologoijensis, and finally became C. antiquitatis.