Subclass †Heterostraci Lankester, 1868
   Family †Cyathaspididae Kiaer, 1932, nom. praeval.
     1 Subfamily †Tolypelepidinae Strand, 1934 (1932), nom. praeval. [paraphyletic]
     1.n Subfamily †Cyathaspidinae [paraphyletic]
     1.n.n.1 Subfamily †Irregulareaspidinae Denison, 1964
     1.n.n.2.1 Subfamily †Anglaspidinae Kiaer, 1932
     1.n.n.2.2.1 Subfamily †Americaspidinae Fowler, 1947
     1.n.n.2.2.2.1 Subfamily †Boothiaspidinae Elliot, 2016
     1.n.n.2.2.2.2 Subfamily †Poraspidinae Denison, 1964