Vertebrata Cuvier, 1812 - vertebrates see Infraphylum Vertebrata Lamarck, 1801
   Gnathostomata
     Class Chondrichthyes Huxley, 1880 - cartilaginous fishes
       Subclass Elasmobranchii Bonaparte, 1838 - shark-like fishes see Infraclass Elasmobranchii Bonaparte, 1838
         Superorder Euselachii Hay, 1902 see Subclass Euselachii Hay, 1902
           Order Galeomorpha see Superorder Galeomorphii Compagno, 1973
             Suborder Heterodontoidea (Hay, 1902) [monotypic] see Order Heterodontiformes Compagno, 1973
               Family Heterodontidae Gray, 1851 - bullhead sharks