[Neoselachii] Compagno, 1977 - modern sharks and rays see Cohort Neoselachii Compagno, 1977
   Order Hexanchiformes Compagno, 1973 - six-gill sharks
     1 Family Chlamydoselachidae Garman, 1884 [monotypic] - frill sharks
     2 Family Hexanchidae Gray, 1851 - cow sharks