[Phylum] Chordata Bateson, 1885 - chordates
   Subphylum Craniata auct.
     Infraphylum Vertebrata Lamarck, 1801 - vertebrates
       Superclass Gnathostomata Gegenbaur, 1874 - jawed vertebrates
         Class Chondrichthyes Huxley, 1880 - cartilaginous fishes
           Subclass Euselachii Hay, 1902 - sharks, rays, and related fossils
             Infraclass Elasmobranchii Bonaparte, 1838
               Superorder Galeomorphi Compagno, 1973
                 Order †Synechodontiformes Duffin & Ward, 1993
                   Family †Palaeospinacidae Regan, 1906
                     1 Genus †Palaeospinax Egerton, 1872, nom. dub.
                     2 Genus †Synechodus Woodward, 1888
                     3 Genus †Orthacodus Woodward, 1889, nom. illeg. see Genus Sphenodus Agassiz, 1843
                     4 Genus †Paraorthacodus Glickman, 1957