Kingdom [Animalia] Linnaeus, 1758 - animals
   Subkingdom Metazoa Haeckel, 1874 see Kingdom Animalia Linnaeus, 1758
     Division Eumetazoa Butschli, 1910 see Subkingdom Eumetazoa Butschli, 1910
       Subdivision Bilateralia
         Phylum Chordata Bateson, 1885 - chordates
           Subphylum Vertebrata Cuvier, 1812 - vertebrates
             Superclass Agnatha Haeckel, 1895 see Class Agnatha Cope, 1889
               Class Cyclostomata Richards
                 Subclass Petromyzones see Order Petromyzontiformes Berg, 1940
                   1 Family Petromyzonidae Bonaparte, 1831 see Family Petromyzontidae Bonaparte, 1832