Order †Pachycephalosauria Maryañska & Osmólska, 1974 see Infraorder Pachycephalosauria Maryañska & Osmólska, 1974 Family †Pachycephalosauridae Sternberg, 1945 Genus †[Hanssuesia] Sullivan, 2003 1 †Hanssuesia sternbergi (Brown & Schlaikjer, 1943) R.M. Sullivan, 2003