Ornithischians are abundant in the Scollard Lance, Laramie, Lance, Denver, and Hell Creek Formation. The main groups of ornithischians are ankylosaurians, ornithopods, ceratopsians, and pachycephalosaurians. Three ankylosaurians are known, "Ankylosaurus", "Denversaurus", and possibly a species of "Edmontonia" or an undescribed genus. Multiple genera of ceratopsians are known from the formation other than "Triceratops", the leptoceratopsid "Leptoceratops", and the chasmosaurine ceratopsids "Torosaurus", "Nedoceratops" and "Tatankaceratops". Ornithopods are common in the Hell Creek Formation, and are known from several species of the ornithopod "Thescelosaurus" and the hadrosaurids "Edmontosaurus", and a possible species of "Parasaurolophus". Several pachycephalosaurians have been found in the Hell Creek Formation and in similar formations. Among them are the derived pachycephalosaurids "Stygimoloch", "Dracorex", "Pachycephalosaurus", "Sphaerotholus", and an undescribed specimen from North Dakota. The first two might be junior synonyms of "Pachycephalosaurus".