Ankylosaurus is a genus of armored dinosaur. The genus name means "fused lizard", and the specific name means "great belly". A handful of specimens have been excavated to date, but a complete skeleton has not been discovered. Possibly the largest-known ankylosaurid, Ankylosaurus is estimated to have been between 20 and 26 ft long. It was an herbivore from the Upper Cretaceous Period.
It walked on four legs and its body was heavily armoured with rather smooth horn covered bone plates, embedded in its skin.