New material of Hispanotherium matritense (Rhinocerotidae, Perissodactyla) from Laogou of Hezheng County (Gansu, China), with special reference to the Chinese Middle Miocene elasmotheres

New rhinocerotid teeth from Laogou in Hezheng (Gansu, China) are described and identified as Hispanotherium matritense. Comparing the other Chinese Middle Miocene elasmotheres with material of H. matritense from Iberian localities and Laogou, we confirm the synonymy proposed previously for the species Hispanotherium lintungensis, Tesselodon fangxianensis, Caementodon tongxinensis and Huaqingtherium qiui. The larger size of Hispanotherium tungurense proves that it is a different species from H. matritense. The age of Laogou fauna corresponds to MN6. Paleoenvironments of H. matritense in China include rivers and lakes, which are somewhat different from the arid environment in the Iberian Peninsula. The origin of the Hispanotherium lineage may be in southwestern Europe. After that, it dispersed eastward to Asia.