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
         Myopterygii - myopterygians
           Superclass Gnathostomata Gegenbaur, 1874 - jawed vertebrates
             Grade Teleostomi Bonaparte, 1836
               Class †Acanthodii Owen, 1846
                 Order †Ischnacanthiformes Berg, 1940
                   Family †Ischnacanthidae Woodward, 1891
                     1 Genus †Atopacanthus Hussakof & Bryant, 1920
                     2 Genus †Ischnacanthus Powrie, 1864
                     3 Genus †Marsdenius Wellburn, 1902
                     4 Genus †Xylacanthus Orvig, 1967