An animatronic Pachycephalosaurus in the temporary Dinosaur! exhibit at the Minnesota Zoo.

It's name means "thick-headed lizard" because it had a domed skull that was 10 inches thick.

This 26-foot long dinosaur had long hind limbs and short forelimbs. Standing to a height of around 13 feet, it weighed about two tons.

What They Ate: Pachycephalosaurus was an omnivore – a (plant and meat eater), the Pachycephalosaurus diet remains somewhat of a mystery. Having very small, ridged teeth, they could not have chewed tough, fibrous plants. A diet of leaves, seeds, fruit and insects may have sustained this animal.

Where Fossils Have Been Found In North America: Montana, South Dakota and Wyoming.

What They Did: While it was thought that the skull was used in “ramming rivals” for mating and dominance, research suggests otherwise. The skull is actually porous and fragile when put under pressure. Pachycephalosaurus tails were very stiff and interwoven, with powerful tendons most likely used to “butt” predators in defense.

How They Are Doing: Extinct. Lived in the Cretaceous Period, 76-65 million years ago.