Dinosauria Owen 1841 †Ornithischia Seeley 1887 see Order Ornithischia Seeley, 1887 †Genasauria Sereno 1986 †Neornithischia Cooper 1985 †Marginocephalia Sereno 1986 1 †Pachycephalosauria Maryañska & Osmólska 1974 see Infraorder Pachycephalosauria Maryañska & Osmólska, 1974 2 †Ceratopsia Marsh 1890 see Infraorder Ceratopsia Marsh, 1890