living organisms see Clade Biota Wagner 2004 [Wiemann, de Queiroz, Rowe, Planavsky, Anderson, Gogarten, Turner & Gauthier 2020]
   Superkingdom Eukaryotae see Domain Eukaryota Chatton, 1925
     Kingdom Animalia Linnaeus, 1758 - animals
       Subkingdom Eumetazoa Butschli, 1910 see [unranked] Eumetazoa Bütschli, 1910
         Phylum Chordata Bateson, 1885 - chordates
           Subphylum Vertebrata Cuvier, 1812 - vertebrates
             Class Chondrichthyes Huxley, 1880 - cartilaginous fishes
               Subclass Elasmobranchii Bonaparte, 1838 - shark-like fishes
                 Cohort Euselachii Hay, 1902 - spined sharks and relatives see Infraclass Euselachii Hay, 1902
                   Subcohort Neoselachii Compagno, 1977 - modern sharks and rays see Cohort Neoselachii Compagno, 1977
                     Superorder Squalomorphii (Compagno, 1973) see Division Squalea (Shirai, 1996)
                       Order Hexanchiformes Compagno, 1973 - six-gill sharks
                         Suborder Hexanchoidei (Hay, 1902)
                           Family Hexanchidae Gray, 1851 - cow sharks
                             1 Genus Hexanchus Rafinesque, 1810
                             2 Genus Notorynchus Ayres, 1855
                             3 Genus Heptranchias Rafinesque, 1810