Pachycephalosaurus

About Pachycephalosaurus

Pachycephalosaurus had a super-thick, dome-shaped head covered in bony bumps. It lived alongside T. rex at the very end of the age of dinosaurs.

Pachycephalosaurus wyomingensis was the largest known pachycephalosaur, living in western North America in the last few million years of the Cretaceous. Its skull roof was up to about 22 cm thick, and whether it used that dome for head-butting is one of the liveliest debates about dinosaur behaviour.

Did you know?

1. The top of Pachycephalosaurus's head was about as thick as a big dictionary!
2. Its dome was ringed with bony bumps and little spikes.
3. It walked on two legs and was about as long as a car.
4. It lived at the same time and place as T. rex and Triceratops.

1. Most fossils are skull domes, because the thick bone survived better than the rest of the skeleton; the size of the whole animal is estimated from relatives.
2. In 2004 a bone-tissue study argued the domes were too spongy for head-butting and were mainly for display, but later computer stress models and a 2013 survey of healed injuries on domes support some form of head or flank butting.
3. Some scientists think Dracorex and Stygimoloch, which have flatter heads and longer spikes, may be juvenile Pachycephalosaurus, while others argue they are separate animals; the debate is unresolved.
4. Its teeth were small and leaf-shaped, so most experts see it as a plant-eater, though a few have suggested it may also have eaten fruit, seeds or occasional small animals.

Myth or fact?