Class Bivalvia Linnaeus, 1758 - bivalves Subclass Autobranchia Grobben, 1894 Superorder Heteroconchia Gray, 1854 Clade Palaeoheterodonta Newell, 1965 Order Trigoniida Dall, 1889 1 Superfamily †Beichuanioidea Liu & Gu, 1988 [monotypic] 2 Superfamily †Megatrigonioidea van Hoepen, 1929 3 Superfamily †Myophorelloidea Kobayashi, 1954 4 Superfamily Trigonioidea Lamarck, 1819