← Rex's Notes
Pachycephalosaurus
Skull like a bowling ball.
Said: PACK-ee-SEF-uh-loh-SOR-us
Era: Cretaceous · 70 to 66 million years ago
Diet: Omnivore
Habitat: Upland forests of western North America
Size: about the length of a small car.
What it was like
Its skull was 25 centimeters of solid bone, thicker than a brick wall. It probably bashed sides with rivals, like a bighorn sheep.
What we know now
The head-butting hypothesis is partially supported by recent histology showing healed skull lesions consistent with intraspecific combat, though biomechanical analyses argue against high-speed direct ramming. The dome thickens with age and is sexually dimorphic. Diet is debated; sharp anterior teeth and leaf-shaped cheek teeth suggest omnivory.
Notes
- Some bumpy nubs around the dome may have been horn-like display structures.
- Stygimoloch and Dracorex are now thought to be juvenile growth stages.
- Despite the impressive skull, the brain was small and tucked low.