Fishes
   Class Elasmobranchii Bonaparte, 1838 see Subclass Elasmobranchii Bonaparte, 1838
     Order Hexanchiformes Compagno, 1973 - six-gill sharks
       Family Hexanchidae Gray, 1851 - cow sharks
         1 Genus Heptanchus Müller & Henle, 1841
         2 Genus Heptranchias Rafinesque, 1810
         3 Genus Hexanchus Rafinesque, 1810
         4 Genus Monopterhinus Blainville, 1816
         5 Genus Notidanus Cuvier, 1816
         6 Genus Notorynchus Ayres, 1855