This dinosaur, unlike other, is a different type of dinosaur, with a 7 inch puffed head, used for defensive purposes. Small in size gave it advantage, it made it extremely agile. Agility made it faster, thus saving it from predators. It’s puffed head was used for butting, and even for territorial defence. This dino, was herbivore, and ate low lying plants.  This dino had an incredibly small arms, that was rarely even visible. Pachycephalosaurs were herding dinosaurs that lived in small groups in coastal and upland regions. Running was probably the first line of self-defense. Pachycephalosaurus lived during the late Cretaceous period, about 76 to 65 million years ago, toward the end of the Mesozoic, the Age of Reptiles. Among the contemporaries of Pachycephalosaurus were Albertosaurus and  Tyrannosaurus rexAnkylosaurus (an armored herbivore), Parasaurolophus, Corythosaurus (a crested dinosaur), and Dryptosaurus (a leaping dinosaur). Pachycephalosaurs probably evolved from Hypsilophodon, a small, agile, bipedal herbivore. Pachycephalosaurus was an herbivore, eating soft plants, fruit, and seeds. Its teeth were small and sharp. Pachycephalosaurus walked on two legs, and was not a very fast dinosaur. When it walked or ran, it probably held its back level to the ground. It may have gone on all fours to forage for low-lying plants. Pachycephalosaurus was discovered in 1938 by William Winkley on the family ranch outside of Ekalaka, Montana, USA. It was named Pachycephalosaurus in 1943 by Barnum Brown and Erich M. Schlaikjer. Although complete fossils are rare, many thick skull fragments have been found. Pachycephalosaurus and other pachycephalosaur fossils have been found in Alberta, Canada, the western United States, the Isle of Wight, Mongolia and Madagascar.