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
               Family †Mayomyzontidae Bardack & Zangerl, 1971
                 ?Genus †Hardistiella Janvier & Lund, 1983 [monotypic]
                   †Hardistiella montanensis Janvier & Lund, 1983