The unique Pachycephalosaurus had a thick, dome-shaped head with some remains measuring up to 10 inches thick. While it had been believed that the Pachycephalosaurus used its thick skull to ram head-to-head against other males and predators as defense and as a sign of dominance, further studies have disproven this myth. The domed area of its skull was actually made of porous and fragile bone that would have crumpled had two skulls collided. All of the remains found so far show no signs of scarring, leading scientists to believe that Pachycephalosaurus never rammed its head into anything as hard as its own skull. More likely, it would ram another or a predator in the side, damaging internal organs and causing massive bruises while suffering little to no damage itself.

The dome-headed dino would not automatically start ramming a predator, though. Running was its first line of defense and, despite traveling in herds, it would much rather flee than risk its own life. Two powerful hind legs carried...