Phylum Mollusca Linnaeus, 1758 - molluscs Class Bivalvia Linnaeus, 1758 - bivalves Subclass Palaeoheterodonta Newell, 1965 see Clade Palaeoheterodonta Newell, 1965 Order Trigonida orth. inval. [monotypic] Superfamily Trigonoidea orth. inval. [monotypic] see Superfamily Trigonioidea Lamarck, 1819 1 Family Trigoniidae Lamarck, 1819 [monotypic]