[Phylum] Chordata Bateson, 1885 - chordates
   Subphylum Craniata auct.
     Infraphylum Vertebrata Lamarck, 1801 - vertebrates
       Superclass Gnathostomata Gegenbaur, 1874 - jawed vertebrates
         Class †Acanthodii Owen, 1846 - acanthodians
           Order †Ischnacanthiformes Berg, 1940
             1 Family †Tetanopsyridae Gagnier, Hanke & Wilson, 1999
             2 Family †Ischnacanthidae Woodward, 1891
             3 Family †Acritolepidae Valiukevičius & Burrow, 2005
             4 Family †Poracanthodidae Vergoossen, 1997