Order †Pachycephalosauria Maryañska & Osmólska, 1974 see Infraorder Pachycephalosauria Maryañska & Osmólska, 1974
   Family †Pachycephalosauridae Sternberg, 1945
     †Pachycephalosaurini Sullivan, 2003
       Genus †"Troödon" Leidy, 1856 see Genus Troodon Leidy, 1856, nom. dub.
         1 †Troödon wyomingensis Gilmore, 1931 see Troodon wyomingensis Gilmore, 1931
         2 †Troödon bexelli Bohlin, 1953 see Troodon bexelli Bohlin, 1953