Middle Miocene elasmotheriine Rhinocerotidae from China and Mongolia: taxonomic revision and phylogenetic relationships.

Eight elasmotheriine rhinocerotid species have been described from the Middle Miocene of China and Mongolia. In this paper a revised taxonomy is presented based on direct observation and comparison of the available material. A phylogenetic analysis based on 282 morphological characters has led to the reappraisal of Procoelodonta Matthew, 1931, Caementodon Heissig, 1972 and Huaqingtherium Huang & Yan, 1983. The genus Procoelodonta is split into three subgenera: P. (Procoelodonta ) Matthew, 1931, P. (Begertherium ) Beliaeva, 1971, and P. (Pasalarhinus subg. n). The genus Caementodon is split into two subgenera: C. (Caementodon ) Heissig, 1972 and C. (Beliajevina ) Heissig, 1974. Four species are assumed to have occurred in the Middle Miocene within the area studied: Procoelodonta (Procoelodonta ) mongoliense (Osborn, 1924), ‘P. ’ (Begertherium ) borissiaki (Beliaeva, 1971), ‘Caementodon ’ (Beliajevina ) fangxianense (Yan, 1979) and Huaqingtherium lintungense (Zhai, 1978) (=‘Caementodon tongxinensis ’ Guan, 1988 =‘Huaqingtherium qiui ’ Guan, 1993 =‘Hispanotherium tungurense ’ Cerdeño, 1996). Shennongtherium hypsodontus Huang & Yan, 1983 is removed from the Elasmotheriina, owing to dental characters which suggest that it is a teleoceratine. The distribution of the main characters later seen in Elasmotherium is briefly discussed. The persistence and diversity of the Elasmotheriina throughout the Middle Miocene help explain how minute brachyodont animals gave rise to the mammoth-sized hypsodont Elasmotherium. [ABSTRACT FROM AUTHOR]