The Ankylosaurus was named by paleontologist, Barnum Brown, in 1908. The name Ankylosaurus means fused lizard. The Ankylosaurus got its name from its heavy armor which covers its entire body. Even its eyelids were hardened. The 33 foot dinosaur had a club-like tail. The tail was hard and heavy and was probably a weapon of defense against vicious predators. The Ankylosaurus weighed in at four to five tons which is pretty heavy. The Ankylosaurus was only six feet wide and four feet tall. The Ankylosaurus's head was shaped like an equilateral triangle. It was two and a half feet long and wide. Another method of defense for the Ankylosaurus is the spikes that cover its entire back. When the Anklyosaurus was attacked it would lay and press its body against the ground. In this position the Ankylosaurus was invincible. The Ankylosaurus was a huge and heavy dinosaur, but it had small teeth and ate only plants. It needed a lot of food to keep itself going. The Ankylosaurus died out during the Cretaceous-Tertiary extinction. The extinction occurred approximately 65 million years ago.