Phylum Mollusca Linnaeus, 1758 - molluscs Class Bivalvia Linnaeus, 1758 - bivalves Subclass Palaeoheterodonta Newell, 1965 see Clade Palaeoheterodonta Newell, 1965 Order Unionida Gray, 1854 Superfamily Unionoidea Rafinesque, 1820 Family Hyriidae Swainson, 1840 Subfamily Rectidentinae Modell, 1942 [monotypic] Genus Rectidens Simpson, 1900