Was heavily armoured with osteoderms fused to its skin, it even had bony plates over its eyelids. It had two triangular horns on its head and two ridges of spines running down its back. It also had a tail club made out of osteoderms fused to the end vertebrae. This was probably used as defense against predators and for defense of their territory. The only place that Ankylosaurus was vulnerable was its stomach, which did not have any osteoderms. It had 72 to teeth that were leaf shaped and not meant for grinding as they probably did not eat large plants.
Herbivores. Typically, ankylosaur fossils are found as individual specimens. Their tank-like bodies and short legs were likely inefficient for long-distance walking in herds suggesting that they lived a solitary lifestyle with a limited home range, similar to that of modern-day rhinoceros. To sustain itself Ankylosaurus probably had to eat large amounts of plants, in order to digest all of its food Ankylosaurus probably used fermentation to break it down.
Ankylosaurus was named by Barnum Brown in 1908; it is monotypic, containing only A. magniventris. The specimen (found by collector Peter Kaisen) consisted of the upper part of a skull, two teeth, part of the shoulder girdle, cervical, dorsal, and caudal vertebrae, ribs, and more than thirty osteoderms (armor plates). A handful of specimens have been excavated to date, but a complete skeleton has not been discovered. Though other members of Ankylosauria are represented by more extensive fossil material, Ankylosaurus is often considered the archetypal member of its group, despite having some unusual features.
Specimens of Ankylosaurus have been found in the Hell Creek, Lance, Scollard, Frenchman, and Ferris formations, but it appears to have been rare in its environment. Although it lived alongside a nodosaurid ankylosaur, their ranges and ecological niches do not appear to have overlapped, and Ankylosaurus may have inhabited upland areas. Ankylosaurus also lived alongside dinosaurs such as Tyrannosaurus, Triceratops, and Edmontosaurus.