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Pachycephalosaurus had a small muzzle that ended in a pointed beak. The teeth were tiny, with leaf-shaped crowns. The head was supported by an S- or U-shaped neck. [26] Younger individuals of Pachycephalosaurus might have had flatter skulls and larger horns projecting from the back of the skull. As the animal grew, the horns shrunk and rounded ...
Along with Ceratopsia, it makes up the clade Marginocephalia. With the exception of two species, most pachycephalosaurs lived during the Late Cretaceous Period, dating between about 85.8 and 66 million years ago. [3] They are exclusive to the Northern Hemisphere, all of them being found in North America and Asia.
There is also evidence of advanced adductor musculature that extends from a large coronoid process on the mandible up to the ceratopsian frill, which would increase chewing force. [15] Pachycephalosaurs had gastroliths to help in digestion of food, but only primitive ceratopsians, such as Psittacosaurus, have been found to have gastroliths. [16]
Peter Dodson argued that the rarity of pachycephalosaurs in the fossil record suggests that they preferred dryer habitats farther from coasts and rivers where ceratopsians and ornithopods lived and where fossilization is more likely to occur. He also observed that many pachycephalosaur fossils show signs of damage by transport over significant ...
Pachycephalosaurs are today grouped with the horned ceratopsians in the group Marginocephalia. Stegoceras itself has been considered basal (or "primitive") compared to other pachycephalosaurs. Stegoceras was most likely herbivorous, and it probably had a good sense of smell.
Ceratopsidae (sometimes spelled Ceratopidae) is a family of ceratopsian dinosaurs including Triceratops, Centrosaurus, and Styracosaurus. All known species were quadrupedal herbivores from the Upper Cretaceous. All but one species are known from western North America, which formed the island continent of Laramidia during most of the Late ...
Ceratopsians ranged in size from 1 meter (3.3 feet) and 23 kilograms (51 pounds) to over 9 meters (30 feet) and 9,100 kg (20,100 lb). [citation needed] Ceratopsians are easily recognized by features of the skull. On the tip of a ceratopsian upper jaw is the rostral bone, an edentulous (toothless) ossification, unique to ceratopsians.
Marginocephalia is a clade of ornithischian dinosaurs that includes some of the most well-known Mesozoic animals, such as Triceratops and Pachycephalosaurus. The group is united by, and is named for, the presence of a bony margin formed mostly from the parietal and squamosal bones at the posterior end of the skull.