†Placodermi McCoy, 1848 †Arthrodira Woodward, 1891 †Brachythoraci Gross, 1932 †Eubrachythoraci Miles, 1971 †Coccosteomorphi Stensiö, 1944 Family †Coccosteidae Traquair, 1888 Genus †Coccosteus Miller, 1841 1 †Coccosteus cuspidatus Miller, 1841 ex Agassiz