Class †Placodermi McCoy, 1848
   Order †Arthrodira Woodward, 1891 see [unranked] Arthrodira Woodward, 1891
     †Aspinothoracida see [unranked] Aspinothoracidi Stensiö, 1959
       1 Family †mylostomatids? Woodward, 1891
       2.1 Genus †Gorgonichthys Claypole, 1892
       2.2.1 Genus †Heintzichthys Whitley, 1933
       2.2.2 Family †Selenosteidae Dean, 1901