Order †Ornithischia Seeley, 1887 Parvorder †Genasauria Sereno, 1986 see Clade Genasauria Sereno 1986 Nanorder †Cerapoda Sereno, 1986 see Suborder Cerapoda Sereno, 1986 Hypoorder †Marginocephalia Sereno, 1986 see Clade Marginocephalia Sereno 1986 Suborder †Ceratopsia Marsh, 1890 see Infraorder Ceratopsia Marsh, 1890 Genus †Psittacosaurus Osborn, 1923