†Placodermi McCoy, 1848 †Arthrodira Woodward, 1891 †Brachythoraci Gross, 1932 †Eubrachythoraci Miles, 1971 †Pachyosteomorphi Stensiö, 1944 Superfamily †Dunkleosteoidea Stensiö, 1963 Family †Panxiosteidae Wang, 1979 ?Genus †Plourdosteus Ørvig, 1951 1 †Plourdosteus canadensis (Woodward, 1892)