Predators would have had to flip the squat, four-legged animal over, exposing its unprotected underbelly, to find a weak spot. Ankylosaurus's distinctive plates did more than deflect blows—they ...

Pachycephalosaurus wyomingensis was the largest of the pachycephalosaurids—"thick-headed dinosaurs"—which featured extremely thick skullcaps. The top of a Pachycephalosaurus skull could be 9 ...