Superphylum Deuterostomia Grobben, 1908 - deuterostomes see Infrakingdom Deuterostomia Grobben, 1908
   Phylum Chordata Bateson, 1885 - chordates
     Subphylum Craniata auct.
       Vertebrata Lamarck, 1801 - vertebrates see Infraphylum Vertebrata Lamarck, 1801
         Superclass Petromyzontomorphi [monotypic]
           Class Petromyzontida [monotypic] - lampreys see Class Petromyzonti
             Order Petromyzontiformes Berg, 1940 - lampreys
               1 Family Petromyzontidae Bonaparte, 1831, sedis mutabilis - lampreys
               2 Family Geotriidae Gill, 1893, sedis mutabilis [monotypic] - pouched lampreys
               3 Family Mordaciidae Gill, 1893, sedis mutabilis [monotypic] - southern topeyed lampreys
               4 Family †Mayomyzontidae Bardack & Zangerl, 1971