Ankylosaurus was a huge armored dinosaur, measuring about 25-35 feet (7.5-10.7 m) long, 6 feet (1.8 m) wide and 4 feet (1.2 m) tall; it weighed roughly 3-4 tons. Its entire top side was heavily protected from carnivores with thick, oval plates embedded (fused) in its leathery skin, 2 rows of spikes along its body, large horns that projected from the back of the head, and a club-like tail. It even had bony plates as protection for its eyes. Only its under-belly was unplated. Flipping it over was the only way to wound it. Ankylosaurus had four short legs (the rear legs were larger than the front legs), a short neck, and a wide skull with a tiny brain. Ankylosaurus was the last of the ankylosaurids(armored dinosaurs) to evolve, and the biggest. It lived in the late Cretaceous period, about 70-65 million years ago. Among its contemporaries were the large meat-eating Tyrannosaurus, Tarbosaurus, and Deinonychus. Short of being flipped over, the Ankylosaurus was well protected from these predators, and could even defend itself with its club-like tail. This huge, extremely heavy reptile was an herbivore (it ate only plants). It had to eat a huge amount of low-lying plant material to sustain itself so its gut must have been very large. It probably had a fermentation compartment to aid in the digestion of the tough plant material, producing prodigious amounts of gas! Ankylosaurus was however a dumb, dinosaur, whose IQ, was very low among the dinosaurs.