Superphylum Deuterostomia Grobben, 1908 - deuterostomes see Infrakingdom Deuterostomia Grobben, 1908
   Phylum Chordata Bateson, 1885 - chordates
     Subphylum Craniata auct. see Subphylum Vertebrata Cuvier, 1812
       Vertebrata (Lamarck, 1801) - vertebrates see Subphylum Vertebrata Cuvier, 1812
         Superclass Petromyzontomorphi [monotypic]
           Class Petromyzontida [monotypic] - lampreys
             Order Petromyzontiformes Berg, 1940 - lampreys
               1 Family Petromyzontidae Bonaparte, 1832, sedis mutabilis - lampreys
               2 Family Geotriidae Gill, 1893, sedis mutabilis [monotypic]
               3 Family Mordaciidae Gill, 1893, sedis mutabilis [monotypic]
               4 Family †Mayomyzontidae Bardack & Zangerl, 1971