[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 †Eugeneodontiformes Zangerl, 1981
               Suborder †Edestoidei
                 Family †Helicoprionidae Karpinsky, 1911
                   1 Genus †Helicoprion Karpinsky, 1899
                   2 Genus †Agassizodus St. John & Worthen, 1875