[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 †Helodontiformes Patterson, 1965 [monotypic]
               Family †Helodontidae Jaekel, 1898
                 1 Genus †Helodus Agassiz, 1838