Order †Ornithischia Seeley, 1887 Count: - Parvorder †Genasauria Sereno, 1986 see Clade Genasauria Sereno 1986 Count: - Nanorder †Cerapoda Sereno, 1986 see Suborder Cerapoda Sereno, 1986 Count: - Hypoorder †Marginocephalia Sereno, 1986 see Clade Marginocephalia Sereno 1986 Count: - 1 Suborder †Pachycephalosauria Maryañska & Osmólska, 1974 see Infraorder Pachycephalosauria Maryañska & Osmólska, 1974 Count: - 2 Suborder †Ceratopsia Marsh, 1890 see Infraorder Ceratopsia Marsh, 1890 Count: -