Ankylosaurus was the largest of all the armored dinosaurs. It lived about 70 to 65 million years ago. It was a very large dinosaur. It grew to be about 30 feet long, six feet wide and four feet tall. That’s about the size of a school bus. It weighed between three and four tons. Ankylosaurus grew thick, bony plates over its entire body. Its head was also covered with bony plates and spikes. There were even bony plates around its eyelids. The plates grew on top of each other, so Ankylosaurus could move around without showing its skin. Two rows of spikes grew along its back and two large horns grew out of its head. It was a well-protected dinosaur.
In addition to its spikes, Ankylosaurus had a heavy club at the end of its tail. It carried its tail straight out from behind, off the ground, even though it was heavy. When a predator came too close, Ankylosaurus would whip its deadly tail around. Only its belly was soft and unprotected. If a predator wanted to attack Ankylosaurus, it would have the best chance if it flipped this heavy dinosaur onto its back. Like a turtle, Ankylosaurus had a hard time getting back on its feet again. This is how it got its name, which means “stiff lizard”. Its body was close to the ground because of its short, stumpy legs. Its hind legs were bigger than its front legs. Ankylosaurus was not a very intelligent dinosaur. The hole in its skull was very small, so there wasn’t much room for a large brain.
This dinosaur was an herbivore, meaning that it only ate plants. Since it wasn’t very tall, it mostly ate plants that grew low to the ground. It was probably too heavy to stand up on its hind legs to reach for food on trees. It had to eat lots and lots of plants to stay alive. It probably had a second stomach that helped digest the plant material. This second stomach was called a gizzard. Ankylosaur trackways have been found in Bolivia, South America. Paleontologists studying these footprints think that this dinosaur could run pretty quickly, even though it had so much heavy armor. Fossils have also been found in Montana, North America and in Alberta, Canada. Ankylosaurus, along with the rest of the other dinosaurs, died 65 million years ago. This was an unusual time in the earth’s history, called the K-T boundary, when many, many dinosaurs died out at the same time.