Dino profile
Pachycephalosaurus
the dinosaur with a dome-shaped head
Pachycephalosaurus was a dinosaur that walked on two legs. You can spot it by its very thick skull, rounded like a dome.
Its ID card
- Its name
- “Thick-headed lizard”. [1]
- When
- At the very end of the Cretaceous, about 70 to 66 million years ago, just before the dinosaurs disappeared. [1][2]
- Where
- In North America: in the United States (Montana, South Dakota, Wyoming) and in Canada (Alberta). [1][2]
- What it ate
- Probably plants: leaves, fruit and seeds. This is not certain: maybe it also ate meat. [1][2]
- Its family
- The pachycephalosaurs, thick-headed dinosaurs. [1]
A dome-shaped head
The top of its skull formed a big bony dome, more than 20 centimeters thick. All around it, it had bumps and small spikes. [1][2]
What was this dome for? Scientists don't agree. Some think these dinosaurs butted heads, like rams. Others think they bumped their heads against each other's sides instead. [1][2]
Others still think the dome was mostly for showing off, or for several things at once, like deer antlers. [1]
In 2013, scientists found signs of bone infection on 22% of the domes they studied. For them, it is a clue that these dinosaurs fought each other. [2]
A dino that changes as it grows
It walked on its two back legs. It had a beak for cutting plants and small teeth. [1][2]
Some of its front teeth look like those of meat-eating dinosaurs. That's why some scientists think it maybe ate meat too. [1][2]
Stygimoloch and Dracorex were first seen as different dinosaurs. Today, most scientists think they are young Pachycephalosaurus: as they grew, they lost spikes and their dome grew. [1][2]
It lived in a warm, damp area, full of flowering plants. Tyrannosaurus, Triceratops and Ankylosaurus lived in the same place. [1]
Its discovery
Around 1860, American collector Ferdinand Hayden finds a small piece of bone. In 1872, it is given the name Tylosteus: at the time, people think it is a piece of a reptile's shell. [1][2]
In 1943, after other fossils are discovered, Barnum Brown and Erich Schlaikjer create the name Pachycephalosaurus. [1][2]
Later, people realize that the piece of bone Hayden found also came from a Pachycephalosaurus. In 1986, it is decided to keep the name Pachycephalosaurus. [1][2]
Scientists have only described bones from its skull. [2]
In Dino Cosmos
12 Storm Planet
It helps you in its world. One headbutt and the platform lights up again.
Sources
The information on this page comes from these sources:
- Pachycephalosaurus, Dino Directory, Natural History Museum, London (accessed November 5, 2026).
- Pachycephalosaurus, Wikipedia (English), and the publications it cites: Brown & Schlaikjer 1943, Baird 1979, Sues 1978, Carpenter 1997, Horner & Goodwin 2009, Paul 2010, Peterson et al. 2013, Benson et al. 2014 (accessed November 5, 2026).