[Neoselachii] Compagno, 1977 - modern sharks and rays see Cohort Neoselachii Compagno, 1977 Order Hexanchiformes Compagno, 1973 - six-gill sharks Family Hexanchidae Gray, 1851 - cow sharks Genus Heptranchias Rafinesque, 1810 [monotypic] 1 Heptranchias perloᵀ (Bonnaterre, 1788) - sevengilled shark