Chordata Bateson, 1885 - chordates Class †Ostracophori Order †Heterostraci Lankester, 1868 - heterostracans see Subclass Heterostraci Lankester, 1868 Family †Drepanaspidae [monotypic] see Family Psammosteidae Traquair, 1896 Genus †Drepanaspis Schlüter, 1887