A new Ordoviciannautiloid genus (Variabioceras) in the Xainza area, northern Xizang

The specimens described in the paper are part of the collection of nautiloid fossils from Zhakang east of the Taerma Bridge, Xainza County, Xizang. Three genera and six species are described, including one new genus Variabioceras gen. nov. and its three new species V. typicum gen. et sp. nov., V. zangbeiense gen. et sp. nov. and V. robustum gen. et sp. nov.