Dinosauria Owen 1841 [Padian & May 1993], nom. cl. inval. see Clade Dinosauria Owen 1842 [Langer, Novas, Bittencourt, Ezcurra & Gauthier 2020] Count: - †Ornithischia Seeley 1887 [Padian & May 1993] see Order Ornithischia Seeley, 1887 Count: - †Genasauria Sereno 1986 Count: - †Neornithischia Cooper 1985 Count: - †Marginocephalia Sereno 1986 Count: - †Pachycephalosauria Maryañska & Osmólska 1974 see Infraorder Pachycephalosauria Maryañska & Osmólska, 1974 Count: - †Pachycephalosauridae Sternberg 1945 see Family Pachycephalosauridae Sternberg, 1945 Count: - †Pachycephalosaurinae Sereno 1998 Count: - Genus †Prenocephale Maryañska & Osmólska, 1974 Count: -