Ankylosaurus

Ankylosaurus was a large, armored dinosaur that lived in western North America about 68 to 66 million years ago. Its name means "fused lizard," because many of its bones were joined together into thick plates. Ankylosaurus walked on four legs and ate plants. It was one of the last dinosaurs alive before the great extinction that wiped out all non-bird dinosaurs.

An adult Ankylosaurus was about 20 to 30 feet long, roughly the length of a school bus. It weighed around 4 to 8 tons, as much as a modern elephant. Its body was low and wide, close to the ground like a living tank. Even its eyelids had small bony plates that could close like shutters.

The armor was the most famous thing about this dinosaur. Hundreds of bony lumps, called osteoderms, were set into its thick skin. Rows of these lumps ran down its back and sides. Sharp spikes stuck out from its shoulders and neck. The soft belly, where its skin had no armor, was the only easy place to attack. A hungry predator would have needed to flip the whole dinosaur over, which was probably almost impossible.

The tail ended in a huge club made of fused bone. This club could weigh as much as 60 pounds. Ankylosaurus swung it sideways using strong tail muscles. Scientists think a hard hit from this club could have broken the leg of a Tyrannosaurus rex, which lived in the same time and place. A dinosaur with a broken leg would not survive long, so even a giant predator had good reason to be careful.

Ankylosaurus had a small head with a wide, beaked mouth. Its teeth were tiny and shaped like leaves. It probably clipped low ferns, flowers, and other soft plants, then swallowed them almost whole. A very large gut broke the food down slowly. Some scientists think Ankylosaurus may have eaten insects or roots too, but the evidence is not clear.

Not many Ankylosaurus fossils have been found. Most of what scientists know comes from a handful of skulls and partial skeletons. A full skeleton has never been discovered. Because of this, some details, like the exact shape of its feet and the color of its skin, are still unknown.

Ankylosaurus lived right up to the end of the age of dinosaurs. When an asteroid struck Earth 66 million years ago, this armored tank and almost every other dinosaur disappeared forever.