This herbivore had a mysterious dome of solid bone at the top of its skull, but what for? One old theory is that males had head-butting contests like rams—but their curved necks might not have been able to take the force.
Another theory is that they swung their heavy heads sideways at each other like giraffes. Or perhaps their fancy heads merely served to impress mates and rivals.
Last of the dinosaurs
Pachycephalosaurus lived at the end of the Cretaceous Period and was one of the species wiped out in the dinosaurs’ mass extinction.
■ When: 65 million years ago (Late Cretaceous)
■ Fossil location: N. America
■ Habitat: Forests of N. America
■ Length: 16 ft (5 m)
■ Diet: Plants, soft fruit, seeds
By comparing Pachycephalosaurus’s few fossils with those of its relatives, scientists figure that this dinosaur was about as long as a station wagon. It probably had a bulky body but the long, slender hind legs of a fast runner. Its small teeth suggest a diet of easily digested plants or, perhaps, a mixture of plants and animal foods such as eggs.
DID YOU KNOW…?
Pachycephalosaurus is known only from one complete skull and a few skull fragments. The dome of thick bone on its skull was fringed by bony knobs and spikes, which may have been used for display. Its teeth were tiny and its eyes large.