Class †Placodermi McCoy, 1848 Order †Arthrodira Woodward, 1891 see [unranked] Arthrodira Woodward, 1891 Suborder †Brachythoraci Gross, 1932 †"Migmatocephala" Family †Homostiidae Eastman, 1907 Genus †Homostius Asmuss, 1856 1 †Homostius milleri Traquair, 1888 2 †Homostius arcticus Heintz, 1934 3 †Homostius latus Asmuss, 1856