pachycephalosaur

dinosaur infraorder

Also known as: Pachycephalosauria, bone-headed dinosaur, domehead(Show More)

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July 23, 2026

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*Stegoceras* Skull of the pachycephalosaur *Stegoceras*.

The term "pachycephalosaur" refers to a group of dinosaurs characterized by their thickened, domed skulls. These dinosaurs, known as "bone-headed" or "dome-headed" dinosaurs, were bipedal and primarily found in North America and Asia during the Late Cretaceous period. While some species, like Pachycephalosaurus, grew up to 5 meters (16 feet) long, others were considerably smaller. The exact function of their distinctive cranial domes is debated; theories range from head-butting, similar to modern rams, to species recognition or display. Microscopic analysis of the bone structure suggests the domes were not ideally suited for absorbing impact, leading to alternative hypotheses about their purpose. Pachycephalosaurs are classified within the Ornithischia order, specifically as part of the Cerapoda group.12

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dinosaur
Pachycephalosauria
In important respects the pachycephalosaurs conformed to the basic ornithopod body plan, and there is some evidence that pachycephalosaurs actually evolved from (and are therefore members of) ornithopods, perhaps similar to hypsilophodontids. All of them appear to have been bipedal. They bore the typical…
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In important respects the pachycephalosaurs conformed to the basic ornithopod body plan, and there is some evidence that pachycephalosaurs actually evolved from (and are therefore members of) ornithopods, perhaps similar to hypsilophodontids. All of them appear to have been bipedal. They bore the typical…
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ornithischian
into the Ornithopoda, Pachycephalosauria, and Ceratopsia, though some authorities link the Pachycephalosauria and Ceratopsia together in a group called Marginocephalia. The Thyreophora consisted of the Stegosauria and Ankylosauria and their relatives.
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into the Ornithopoda, Pachycephalosauria, and Ceratopsia, though some authorities link the Pachycephalosauria and Ceratopsia together in a group called Marginocephalia. The Thyreophora consisted of the Stegosauria and Ankylosauria and their relatives.
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