Ankylosaurus

Ankylosaurus was the ultimate defensive machine. Its entire back was covered in osteoderms — bony plates fused directly to the skin — arranged like a natural suit of armor. Even its eyelids were armored. The only vulnerable part of the animal was its underside.

But Ankylosaurus wasn't purely passive. The massive club at the end of its tail — formed from several fused vertebrae and bony knobs — could be swung with enough force to break the leg bones of a T-Rex. Predators attacking from behind faced a genuinely dangerous weapon.

Ankylosaurus lived in the same time and place as T-Rex and Triceratops — the very end of the Cretaceous. It was one of the last dinosaurs. Its fossils are surprisingly rare, which is unusual given how robust its armor was. No complete skeleton has ever been found.

The nasal passages of Ankylosaurus were elaborate, winding through the skull in a complex network. These passages may have warmed and humidified air, or possibly amplified sounds for communication — though this remains speculative.