†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 †Plourdosteus canadensis (Woodward, 1892)