Order †Pachycephalosauria Maryañska & Osmólska, 1974 see Infraorder Pachycephalosauria Maryañska & Osmólska, 1974
   Family †Pachycephalosauridae Sternberg, 1945
     †Stegoceras lambei C.M. Sternberg, 1945 see Colepiocephale lambei (C.M. Sternberg, 1945) R.M. Sullivan, 2003