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Pachycephalosaurus Dinosaur Quick Facts for Kids


Pachycephalosaurus is a genus of pachycephalosaurid dinosaurs. It was an herbivorous or omnivorous creature which is primarily known from a single skull and a few extremely thick skull roofs, though more complete fossils have been found in recent years. Pachycephalosaurus was one of the last non-avian dinosaurs before the Cretaceous–Paleogene extinction event.

  • Another dinosaur, Tylosteus of western North America, has been synonymized with Pachycephalosaurus.
  • The thick skull domes of Pachycephalosaurus and related genera gave rise to the hypothesis that pachycephalosaurs used their skulls in intra-species combat.
  • Pachycephalosaurus is famous for having a large, bony dome atop its skull, up to 25 cm (10 in) thick, which safely cushioned its tiny brain.
  • The skull was short, and possessed large, rounded eye sockets that faced forward, suggesting that the animal had good vision and was capable of binocular vision.
  • Pachycephalosaurus gives its name to the Pachycephalosauria, a clade of herbivorous ornithischian (“bird hipped”) dinosaurs which lived during the Late Cretaceous Period in North America and Asia.
  • Within the tribe Pachycephalosaurini, Pachycephalosaurus is most closely related to Dracorex and Stygimoloch, although these may be juvenile forms of Pachycephalosaurus.
  • Donald Baird, in 1859 or 1860 Ferdinand Vandiveer Hayden, an early fossil collector in the North American West, collected a bone fragment in the vicinity of the head of the Missouri River, from what is now known to be the Lance Formation in southeastern Montana.
  • Its actual nature was not found until Baird restudied it over a century later and identified it as a squamosal (bone from the back of the skull) of Pachycephalosaurus, including a set of bony knobs corresponding to those found on other specimens of Pachycephalosaurus.
  • Because the name Tylosteus predates Pachycephalosaurus, according to the International Code of Zoological Nomenclature Tylosteus would normally be preferred.
  • In 1943, Barnum Brown and Erich Maren Schlaikjer, with newer, more complete material, established the genus Pachycephalosaurus.
  • Peterson et al. (2013) studied cranial pathologies among the Pachycephalosauridae and found that 22% of all domes examined had lesions that are consistent with osteomyelitis, an infection of the bone resulting from penetrating trauma, or trauma to the tissue overlying the skull leading to an infection of the bone tissue.