Class Bivalvia Linnaeus, 1758 - bivalves Subclass Autobranchia Grobben, 1894 Superorder Heteroconchia Gray, 1854 Clade Palaeoheterodonta Newell, 1965 Order Trigoniida Dall, 1889 Superfamily †Beichuanioidea Liu & Gu, 1988 [monotypic] Family †Beichuaniidae Liu & Gu, 1988