Class Bivalvia Linnaeus, 1758 - bivalves Subclass Autobranchia Grobben, 1894 Superorder Heteroconchia Gray, 1854 Clade Palaeoheterodonta Newell, 1965 Order Unionida Gray, 1854 ?Superfamily †Archanodontoidea Modell, 1957 [monotypic] Family †Archanodontidae Modell, 1957