Kingdom Animalia Linnaeus, 1758 - animals
   Phylum Craniata Linnaeus, 1758 see Subphylum Vertebrata Cuvier, 1812
     Pisces
       Class Elasmobranchii Bonaparte, 1838 see Subclass Elasmobranchii Bonaparte, 1838
         Order Hexanchiformes Compagno, 1973 - six-gill sharks
           1 Family Hexanchidae Gray, 1851 - cow sharks
           2 Family Chlamydoselachidae Garman, 1884 - frill sharks