[Phylum] Chordata Bateson, 1885 - chordates
   Subphylum Craniata auct.
     Infraphylum Vertebrata Lamarck, 1801 - vertebrates
       Superclass Gnathostomata Gegenbaur, 1874 - jawed vertebrates
         Class Chondrichthyes Huxley, 1880 - cartilaginous fishes
           Subclass Holocephali Bonaparte, 1832
             Order †Petalodontiformes Zangerl, 1981
               Family †Petalodontidae Newberry & Worthen, 1866
                 1 Genus †Petalodus Owen, 1840
                 2 Genus †Polyrhizodus McCoy, 1848