Class †Placodermi McCoy, 1848 Order †Arthrodira Woodward, 1891 see [unranked] Arthrodira Woodward, 1891 †Aspinothoracida see [unranked] Aspinothoracidi Stensiö, 1959 Genus †Gorgonichthys Claypole, 1892 1 †Gorgonichthys clarki Claypole, 1892