Order †Ornithischia Seeley, 1887 1 Suborder †Ornithopoda Marsh, 1871 see Infraorder Ornithopoda Marsh, 1881 2 Suborder †Stegosauria Marsh, 1877 see Infraorder Stegosauria Marsh, 1877 3 Suborder †Ankylosauria Osborn, 1923 see Infraorder Ankylosauria Osborn, 1923 4 Suborder †Ceratopia