Class †Placodermi McCoy, 1848 Order †Arthrodira Woodward, 1891 see [unranked] Arthrodira Woodward, 1891 †coccosteids Asmuss, 1856 Genus †Coccosteus Agassiz, 1844 1 †Coccosteus cuspidatus Miller, 1841 ex Agassiz