Ankylosaurus is a genus of ankylosaurid dinosaur. Fossils of Ankylosaurus are found in geologic formations dating to the very end of the Cretaceous Period (between about 68–66 million years ago) in western North America. This particular Ankylosaurus is showcased in the Walt Disney feature film Dinosaur.
Ankylosaurus was a large animal by modern standards. The largest known skull measures 64.5 cm (25.4 inches) long and 74.5 cm (29.3 inches) wide. Based on this skull, and using the body proportions of smaller specimens, the largest specimen has been estimated to be 6.25 m (20.5 feet) long, 1.5 m (4.9 feet) wide, and 1.7 m (5.6 feet) tall at the hip.
The body shape was low-slung and quite wide. It was quadrupedal, with the hind limbs longer than the forelimbs. Although its feet are still unknown, comparisons with other ankylosaurs suggest Ankylosaurus probably had five toes on each foot. The skull was low and triangular in shape, wider than it was long. Like other ankylosaurs, Ankylosaurus had small, leaf-shaped teeth, which were the smallest relative to the body size, than in any other ankylosaurid species, and lacked the tooth batteries of the contemporaneous ceratopsid and hadrosaurid dinosaurs. Bones in the skull and other parts of the body were fused, increasing their strength. Ankylosaurus had only one or two natural enemies that shared its habitat; it was contemporary with the famous Tyrannosaurus Rex and the giant dromaeosaurid Dakotaraptor, both of which might have occasionally preyed on Ankylosaurus. As such, its tail club, a weapon of solid bone as wide as a washing machine, was a perfect means of defense against these predators.
In the episode "Dino World", the Callistos discover a planet inhabited by living earth dinosaurs, including a Pteranodon and Ankylosaurus. The Ankylosaurus is Loretta Callisto's favorite dinosaur, which she nicknames "Angie." During their search for Professor Rubicon, Loretta carelessly got to meet a real live Ankylosaurus. However, the Ankylosaurus she found was sleeping, and when it woke up, it got mad and chased Loretta and her family away.