New material of heteromorph ammonites from the Lower Cretaceous of Lhozhag County, southern Tibet and its biostratigraphic implications

Cretaceous ammonites are still poorly known in Tibet, western China. Here we describe a new heteromorph ammonite fauna from the Lower Member of the Lakang Formation in the Lhozhag County, southern Tibet. Material of at least five genera are recognized, including Aspinoceras, ? Hemihoplites, Heteroceratidae gen. et sp. indet, ? Mortoniceras and Parancyloceras, among which three genera are reported from this area for the first time. This ammonite fauna indicates that the age of the Lakang Formation is approximately late Hauterivian to Albian (Early Cretaceous). This study proves that the Lakang Formation was not contemporaneous with the adjacent Gamba Group, which is slightly younger, different from a previous interpretation.