Pachycephalosaurus

Type Species: Pachycephalosaurus wyomingesis
Classification: Dinosauria - Ornithischia - Marginocephalia - Pachycephalosauridae - Pachycephalosaurini
Time Period: late Cretaceous
Location: North America
Diet: Herbivore

Pachycephalosaurus, the arch-type of the pachycephalosaurs, was first discovered in Montana. Its name means "thick headed lizard," and it fits the stereotype. Its known only by a number of large domed skull roofs and one nearly complete skull. This dinosaur's domed head could be up to nine inches thick. As to the purpose of the dome, speculation ran rampant until a couple years ago. Scientists analyzed the domed skulls and discovered indentations similar to those found on the bones of modern animals that head-butt; this has led scientists to conclude that Pachycephalosaurus did indeed butt heads. Males may have engaged in contests for females or territory. A secondary purpose of the skull could've been defensive: a blow from a charging Pachycephalosaurus could splinter bone and rupture organs.

This dinosaur's snout was covered with sharp spikes and dull horns. Its teeth were simple, nothing more elegant than triangular blades used to squash food. This has led paleontologists to speculate that it probably fed on a diet consisting mainly of soft vegetation.