Vertebrata Cuvier, 1812 - vertebrates Gnathostomata Class †Placodermi McCoy, 1848 Order †Arthrodira Woodward, 1891 see Order Arthrodiriformes Grande & Eastman, 1986 Suborder †Brachythoraci Gross, 1932 Superfamily †Heterosteoidea Denison, 1984 [monotypic] 1 Family †Heterosteidae Jaekel, 1903