Very abundant and well-preserved bivalves including Neomegalodon cornutus (sp. nov. ), Quemocuomegalodon oricntus Yao et al. , Q. longitatus Yao et al. and Q. circularis (sp. nov. ), associated with Bakevellia praecursor (Quenstedt), were found from the Quemocuo area, the north part of Qinghai-Tibet Plateau. Accordingly, the fossil-bearing rocks are now placed into the Upper Triassic. These bivalves refer to the Tethy fauna. On the basis of the well-preserved dentitions, a discussion on the classfica-tion of Megalodontidae is also involved.