[Phylum] Chordata Bateson, 1885 - chordates
   Subphylum Craniata auct.
     Infraphylum Vertebrata Lamarck, 1801 - vertebrates
       Superclass Gnathostomata Gegenbaur, 1874 - jawed vertebrates
         Class †Placodermi McCoy, 1848
           Order †Ptyctodontiformes [monotypic]
             Family †Ptyctodontidae Woodward, 1891
               1 Genus †Ptyctodus Pander, 1858, nom. protect.
               2 Genus †Aulacosteus Eichwald, 1846, nom. oblit. see Genus Ptyctodus Pander, 1858, nom. protect.