Pachycephalosaurus, meaning "thick-headed lizard" was a herbivore that walked on 2 legs. It is well-known for the huge 10 inch (25cm) thick bony dome on top of its skull, which was used to cushion its brain whilst the males fought. However, contrary to popular belief, they would not charge at each other head-on and clash their heads together at high speed; their skulls, though thick, could not absorb the impact and would have resulted in massive (if not lethal) brain injuries. Instead, it has by hypothesized that the males would stand side by side and whack their opponent in the ribs with their spicky heads until one of them submitted (this is tactic similarly employed by modern day giraffes, who swing their horned heads into their opponent's neck when they fight). It lived in the Late Cretaceous, about 70-65mya in what is now North America. It died out in the K-T extinction.
Fact File
Height = 1.5 metres (4.5 feet)
The Dino Thunder Zord
Length = 5 metres (16 feet)
Weight = 1 ton
Diet = Herbivorous
Prey
Its teeth were not well designed for eating plants, which has lead to the conclusion that it was an omnivore, eating leaves, berries, seeds, fruits, and insects. As for its place in its ecosystem, it would have be eaten by large predators like T-Rex, and its carcass would very often be scavenged upon by other, small predators.