Pachycephalosaurus

Pachycephalosaurus (name meaning "Thick-Headed Lizard"), often nicknamed Pachy for short, is a genus of pachycephalosaurid dinosaur that originated during the Late Cretaceous period of what is now North America. Measuring 5 meters long and weighing 1 ton, Pachycephalosaurus is one of the world's most recognizable dinosaurs, identifiable by its thick, domed skull.

In the Series 1 finale "End of the Road," a small herd of Pachycephalosaurus, consisting of five adults and eight juveniles were went extint from Late Cretaceous Montana, 65 million years ago.

Era & Discovery
Pachycephalosaurus lived in western North America during the Late Cretaceous period, from 77 – 65 million years ago. Therefore, it died out with the other dinosaurs at the end of the Cretaceous. It shared its environment with other dinosaurs like the hadrosaurs, ceratopsians, and ankylosaurus as well as the Raptors and tyrannosaurs that saw it as prey.

Pachycephalosaurus remains were first discovered in the early 1850s but the dinosaur itself was not named until 1931 by Charles W. Gilmore. Remains have been excavated in Montana, South Dakota, and Wyoming. Pachycephalosaurus has also become one of the most well-known dinosaurs in the world.

Physical Attributes
Pachycephalosaurus is the largest known pachycephalosaur, growing to be about 6 – 7 feet (2 – 2.2 m) tall, measured 15 – 17 feet (4.6 – 5.2 m) long, and weighed around 1 ton (2,000 lbs.) It also possessed long legs and small forearms. Its head was equipped with a small beak, round eyes, and most notably an extremely thick, domed skull roof.

The thick, well over 9-inch skull domes of Pachycephalosaurus was used in infraspecific combat, for example, bashing heads during the mating season, just like the modern ibex do. It is also likely that the animals butted their heads against each other's flanks during the mating season, not unlike giraffes do today. Given the chance, it is also possible they used their heads to defend themselves against predators. Additionally, the head of Pachycephalosaurus is strong enough to burst through a concrete wall.

Behavior & Traits
Pachycephalosaurus lived in small herds of around, at maximum, six other individuals in a single herd. Like many herbivores, Pachycephalosaurus often separated while feeding, which often gave many predators an advantage to attack.

Pachycephalosaurus was generally a highly curious creature, known to follow interesting other animals like humans around and to investigate other things of interest. However, when dealing with its own kind, Pachycephalosaurus could be highly aggressive, attacking other Pachycephalosaurus (or at least what it thought to be them) with a powerful headbutt. Pachycephalosaurus also didn't seem to be highly intelligent, as it could mistake its own reflection for another Pachycephalosaurus.

Much like the larger ceratopsians, Pachycephalosaurus jousted with each other. The young did it for fun, but the adults fought for dominance. With their heads measuring more than 9 inches thick (therefore, making them in comparison to a battering ram) and their spines built to withstand the impact of the hit, it would be very painful to get hit by a Pachycephalosaurus.

Trivia

 * Pachycephalosaurus is the largest pachycephalosaur to be brought to the park.
 * The sound effects of Pachycephalosaurus are that of bull and horse sound effects.