Pachycephalosaurus

Pachycephalosauruses are normally peaceful, herbivorous dinosaurs, but they grow much more violent during mating season, when they fight one another to win over mates and warn away interlopers. They also defend themselves vehemently if potential predators stray too close to their herd. The pachycephalosaurus's skull has a distinctive dome-shaped crown surrounded by numerous blunt, bony horns. This feature, combined with the dinosaur's powerful, compact neck, allows it to make battering-ramlike charges capable of inflicting great damage.

Some humanoid groups have successfully trained pachycephalosauruses as mounts, but the creatures aren't particularly well suited to the task.

Pachycephalosauruses grow to a length of 15 feet and weigh 1,400 pounds.

Remnants from the world's primeval era, these enormous reptilian animals still exist in large numbers in remote wildernesses or underground in magical Darklands caverns. Lizardfolk, orcs, giants, and other humanoids who live near dinosaurs use the animals as mounts, guards, or hunting beasts. Occasionally, rich nobles will collect dinosaurs to display them in menageries, which almost inevitably leads to cast-offs being nursed back to health by druids and other champions of nature. When dinosaurs establish themselves in regions outside their normal habitats, it's often the result of a large collection being released.