[Phylum] Chordata Bateson, 1885 - chordates
   Subphylum Craniata auct.
     Infraphylum Vertebrata Lamarck, 1801 - vertebrates
       Superclass Gnathostomata Gegenbaur, 1874 - jawed vertebrates
         Class †Placodermi McCoy, 1848
           †Arthrodira Woodward, 1891
             Order †Phlyctaeniiformes
               Suborder †Brachythoraci Gross, 1932
                 †Pachyosteomorphi Stensiö, 1944 - pachyosteomorphs
                   1 Family †Rhachiosteidae Stensiö, 1963
                   2 Family †Panxiosteidae Wang, 1979
                   3 Family †Dunkleosteidae Stensiö, 1963, "nom. praeval."
                   4 †Aspinothoracidi Stensiö, 1959