Order †Pachycephalosauria Maryañska & Osmólska, 1974 see Infraorder Pachycephalosauria Maryañska & Osmólska, 1974
   Family †Pachycephalosauridae Sternberg, 1945
     †Pachycephalosaurini Sullivan, 2003
       1 Genus †[Dracorex] Bakker, R. Sullivan, Porter, P. Larson & Saulsbury, 2006
       1.0 Genus †Tylosteus Leidy, 1872, nom. oblit. see Genus Dracorex Bakker, R. Sullivan, Porter, P. Larson & Saulsbury, 2006
       2 Genus †Pachycephalosaurus Brown & Schlaikjer, 1943
       2.0 Genus †"Troödon" Leidy, 1856 see Genus Troodon Leidy, 1856, nom. dub.
       3 Genus †[Stygimoloch] Galton & Sues, 1983
       3.0 Genus †Stenotholus Giffin, Gabriel & Johnson, 1987 see Genus Stygimoloch Galton & Sues, 1983