New species of Tsaidamotherium (Bovidae,Artiodactyla) from China sheds new light on the skull morphology and systematics of the genus

A new species of Tsaidamotherium (Bovidae, Artiodactyla), T. brevirostrum, described here represents only the second discovery of the genus. Tsaidamotherium is a mid-sized late Miocene bovid with an odd-looking plate-like horn-core apparatus so far known only from northwestern China. The holotype of T. brevirostrum is a cranial part of skull from the Liushu Formation (late Miocene) of the Linxia Basin. The new species differs from the type species, T. bohlini, mainly in horn-core morphology, having the frontal horn-cores proper much smaller and less distinctly separated from the plate-shaped posterior portion. Furthermore, the new species has smaller frontal sinuses, but a thicker layer of compact bone beneath the horn-core apparatus as seen in frontal section. A complete skull with a smaller horn-core apparatus is considered to represent a female individual of T. brevirostrum. The facial part of the skull, which is first known for this genus, is very short and high, with a high nasal cavity, strongly retracted nasals, and shortened premaxillae and premolar rows. All this probably suggests that the animal with an enlarged nasal cavity, like the modern Saiga and Budorcas, may have had a special adaptation to the high plateau environment.