[Kingdom] Animalia Linnaeus, 1758 - animals
   Grade Enterozoa
     Grade Cœlomata
       Phylum Vertebrata Lamarck, 1801 see Infraphylum Vertebrata Lamarck, 1801
         Branch Craniata Linnaeus, 1758
           Grade Cyclostoma
             Class Hyperoartia (Müller, 1844)
               1 Genus Petromyzon Linnaeus, 1758