Vertebrata Cuvier, 1812 - vertebrates
   Gnathostomata
     Teleostomi
       Tetrapoda Hatschek & Cori 1896 [Gauthier, Kluge & Rowe 1988]
         Amniota Haeckel, 1866 [Gauthier, Kluge & Rowe 1988] - amniotes
           Class Reptilia Linnaeus, 1758 [paraphyletic] - reptiles
             Subclass Diapsida Osborn, 1903 - diapsids see Clade Diapsida Osborn 1903 [Gauthier & de Queiroz 2020]
               Infraclass Archosauromorpha Huene, 1946 see Clade Archosauromorpha Huene 1946 [Benton 1985], nom. cl. inval.
                 Superorder Archosauria Cope, 1869 - archosaurs see Clade Archosauria Cope 1869 [Gauthier & Padian 1985], nom. cl. inval.
                   †Dinosauria Owen 1841 [Padian & May 1993], nom. cl. inval. see Clade Dinosauria Owen 1842 [Langer, Novas, Bittencourt, Ezcurra & Gauthier 2020]
                     Order †Ornithischia Seeley, 1887
                       Suborder †Ornithopoda Marsh, 1871 see Infraorder Ornithopoda Marsh, 1881
                         1 Family †Fabrosauridae Galton, 1972
                         2 Family †Heterodontosauridae Romer, 1966
                         3 Family †Dryosauridae Stefano, 1903
                         4 Family †Hypsilophodontidae Dollo, 1882
                         5 Family †Iguanodontidae Cope, 1869
                         6 Family †Hadrosauridae Cope, 1869 - hadrosaurs