Phylum Chordata Bateson, 1885 - chordates
   Subphylum Vertebrata Cuvier, 1812 - vertebrates see Infraphylum Vertebrata Lamarck, 1801
     Superclass Agnatha Haeckel, 1895 see Class Agnatha Cope, 1889
       Class Monorhina Haeckel, 1895 see Class Cephalaspidomorphi Kiaer & Stensiö, 1920
         Subclass Hyperoartii see Order Petromyzontiformes Berg, 1940
           1 Superorder †Osteostraci Lankester, 1868 see Class Osteostraci Lankester, 1868
           2 Superorder Petromyzonida