Pachycephalosauria

Pachycephalosaurus (; meaning "thick-headed lizard", from Greek pachys/ "thickness", kephalon/ "head" and sauros/ "lizard") is a genus of pachycephalosaurid ornithischian dinosaur. The type species, P. wyomingensis, is the only known definitive species. The possibly synonymous taxon, Stygimoloch, might represent a distinct genus or a second species, P. spinifer. It lived during the Maastrichtian age of the Late Cretaceous period in what is now western North America. Remains have been excavated in Montana, South Dakota, Wyoming, and Alberta. Mainly known from a single skull and a few

Pachycephalosauria (; from Greek παχυκεφαλόσαυρος for 'thick headed lizards') is a clade of ornithischian dinosaurs. Along with Ceratopsia, it makes up the clade Marginocephalia. Pachycephalosaurs lived exclusively in the Northern Hemisphere during the Cretaceous period, with all members being found in North America and Asia. They were all bipedal, herbivorous/omnivorous animals with thick skulls. Skulls can be domed, flat, or wedge-shaped depending on the species, and are all heavily ossified. The domes were often surrounded by nodes and/or spikes. Partial skeletons have been found of several

Stegoceras is a genus of pachycephalosaurid (dome-headed) dinosaur that lived in what is now North America during the Late Cretaceous period, about 77.5 to 74 million years ago (mya). The first specimens from Alberta, Canada, were described in 1902, and the type species Stegoceras validum was based on these remains. The generic name means "horn roof", and the specific name means "strong". Several other species have been placed in the genus over the years, but these have since been moved to other genera or deemed junior synonyms. Currently only S. validum and S. novomexicanum, named in 2011 fro

Homalocephale (from Greek ὁμαλός, homalos, "even", and κεφαλή, kephalē, "head") is a genus of pachycephalosaurid dinosaur that lived during the Late Cretaceous period of what is now the Nemegt Formation, Mongolia. The genus was described in 1974 by Halszka Osmólska and Teresa Maryańska, and consists of a single species, H. calathocercos. Though Homalocephale has been regarded as a synonym (and juvenile form) of Prenocephale, juvenile specimens of the latter indicate that they were distinct. Homalocephale was long and possibly an omnivore.

Prenocephale (meaning "sloping head") is a genus of small pachycephalosaurid dinosaur from the Late Cretaceous Nemegt Formation of Mongolia. It was similar in many ways to its close relative, Homalocephale.

Alaskacephale is an extinct genus of pachycephalosaurid, a group of dome-headed, herbivorous ornithischian dinosaurs, that lived during the Maastrichtian stage of the Late Cretaceous period in what is now northern Alaska. The genus is one of the few known Arctic dinosaurs and was found in the Prince Creek Formation, which preserves a menagerie of fossils. The only known specimen, a squamosal bone, was found in 1999 and later described in 2005. However, Alaskacephale was not formally named until the next year.

thumb|Life reconstruction|left Wannanosaurus (meaning "Wannan lizard", named after the location where it was discovered) is a genus of basal pachycephalosaurian dinosaur from the Maastrichtian-aged (Upper Cretaceous) Xiaoyan Formation, about 70 million years ago, in what is now Anhui, China. The type species Wannanosaurus yansiensis was described by Hou Lian-Hai in 1977.

Tylocephale (meaning "swollen head") is a genus of pachycephalosaurid dinosaur, a group of dome-headed, herbivorous ornithischians, that lived during the Maastrichtian stage of the Late Cretaceous in what is now Mongolia. It is known from a partial skull and associated mandible that were unearthed in 1971 by a Polish-Mongolian Expedition to the Barun Goyot Formation of the Gobi Desert. The specimen was described in 1974 by Polish paleontologists Teresa Maryańska and Halszka Osmólska as a new genus and species.

Goyocephale is an extinct genus of pachycephalosaurian ornithischian that lived in Mongolia during the Late Cretaceous about 76 million years ago. It was first described in 1982 by Altangerel Perle, Teresa Maryańska and Halszka Osmólska for a disarticulated skeleton with most of a skull, part of the forelimb and hindlimb, some of the pelvic girdle, and some vertebrae. Perle et al. named the remains Goyocephale lattimorei, from the Mongolian гоё (goyo), meaning "decorated", and the Ancient Greek κεφαλή (kephale), for head. The species name honours Owen Lattimore.

Sphaerotholus is a genus of pachycephalosaurid dinosaur from the Upper Cretaceous of the western United States and Canada. To date, five species have been described: the type species, S. goodwini, from the Den-na-zin Member of the Kirtland Formation and possibly the Fossil Forest Member of the Fruitland Formation (Late Campanian) of San Juan County, New Mexico, USA; S. buchholtzae, from the Hell Creek Formation (Late Maastrichtian) of western Carter County, Montana, USA and the Frenchman Formation of Saskatchewan, Canada; S. edmontonensis, from the Horseshoe Canyon Formation of Alberta, Canada

Amtocephale is a genus of pachycephalosaurid dinosaur from early Late Cretaceous (Cenomanian-Coniacian stages) deposits of southern Gobi Desert, Mongolia.

Acrotholus (Greek for "highest dome"- akros meaning highest and tholos meaning dome) is an extinct genus of pachycephalosaurian dinosaur that lived during the Santonian of the late Cretaceous, in the Milk River Formation of Canada. The type species, A. audeti, was named after Roy Audet allowing access to his ranch leading to the discovery of the species. The discovery of this specimen lead to several new revelations in the fossil records questioning the preservation of small-bodied organisms along with the evolution of early pachycephalosaurs. The iconic cranial dome found on Acrotholus makes

Hanssuesia is a genus of pachycephalosaurid dinosaurs from the late Cretaceous period. It lived in what is now Alberta and Montana, and contains the single species Hanssuesia sternbergi. thumb|left|Life restoration Hanssuesia is based on a skull dome originally named Troodon sternbergi by Barnum Brown and Erich Maren Schlaikjer in 1943. The specific name honoured Charles Mortram Sternberg who found the dome in 1928 near Steveville in south Alberta. In 1945, it was transferred to Stegoceras by C.M. Sternberg himself, as a Stegoceras sternbergi.

Colepiocephale (meaning "knucklehead") is a genus of pachycephalosaurid dinosaur from Late Cretaceous (middle Campanian stage) deposits of Alberta, Canada. It was collected from the Foremost Formation. The type species, C. lambei, was originally described by Sternberg in 1945 as Stegoceras lambei, and later renamed by Sullivan in 2003. C. lambei is a domed pachycephalosaur characterized principally by the lack of a lateral and posteriosquamosal shelf, a steeply down-turned parietal, and the presence of two incipient nodes tucked under the posterior margin of the parietosquamosal border.

Gravitholus (meaning 'heavy dome') was a genus of pachycephalosaurid dinosaur from the late Cretaceous period (Campanian stage, around 75 million years ago). It was a pachycephalosaur, and like other pachycephalosaurids the skull roof formed a thick dome made of dense bone, which may have been used in head-butting contests over mates or territory. It lived in what is now Alberta, Canada, and was described in 1979 by W. P. Wall and Peter Galton. The type species is Gravitholus albertae.

Texacephale is a possibly dubious genus of pachycephalosaurid dinosaur from the Campanian stage of the Late Cretaceous. Its fossils come from the Aguja Formation of Big Bend National Park, in Texas, and were described in 2010 by Longrich, Sankey and Tanke. The generic name means Texas + "head" (kephale in Greek) in reference to its place of discovery, and the specific name langstoni honors Wann Langston. It may be a synonym of Stegoceras.

Zavacephale (meaning "origin head") is an extinct genus of pachycephalosaurian dinosaurs known from the Early Cretaceous Khuren Dukh Formation of Mongolia. The genus contains a single species, Zavacephale rinpoche, known from a partial articulated skeleton including a nearly complete skull. It is both the oldest definitive pachycephalosaur known, as well as the most complete. Its skull bears a well-developed dome structure, as seen in most members of the clade.

Platytholus is an extinct genus of pachycephalosaurid dinosaur from the Late Cretaceous (Maastrichtian) Hell Creek Formation of the United States. The genus contains a single species, P. clemensi, known from a partial skull.

Foraminacephale (meaning "foramina head") is a genus of pachycephalosaurid dinosaur from Late Cretaceous (Campanian stage) deposits of Canada.

Brontotholus () is an extinct genus of pachycephalosaurid dinosaur known from the Late Cretaceous (Campanian stage) Two Medicine and Oldman formations of Montana, United States, and Alberta, Canada, respectively. The genus contains a single species, Brontotholus harmoni, known from multiple partial domes.

Sinocephale (meaning ) is a genus of pachycephalosaurid dinosaur that lived in what is now Inner Mongolia, China, during the Cretaceous period. The genus contains a single species, Sinocephale bexelli, which was originally named as a species of the genus Troodon in 1953, and later transferred to the genus Stegoceras in 1964. After decades of being considered dubious, it was re-evaluated in 2021 and recognised as a valid taxon, being given its own genus, Sinocephale. The original holotype was lost, with modern research conducted using rediscovered plaster casts.