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.