Order †Pachycephalosauria Maryañska & Osmólska, 1974 see Infraorder Pachycephalosauria Maryañska & Osmólska, 1974 Family †Pachycephalosauridae Sternberg, 1945 †Pachycephalosaurini Sullivan, 2003 Genus †Pachycephalosaurus Brown & Schlaikjer, 1943 †Pachycephalosaurus wyomingensis (Gilmore, 1931) Brown & Schlaikjer, 1943