Ankylosaurus was the last of the armored dinosaurs (ankylosaurids) to evolve, and the biggest. This plant-eater lived during the late Cretaceous Period, about 70-65 million years ago.

Diet: 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!

Anatomy: 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 4.4 tons (4 tonnes). 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.

Name and Fossils: Ankylosaurus was named by Barnum Brown in 1908. Ankylosaurus fossils have been found in the western USA (Montana) and Canada (Alberta). Two Ankylosaurus skulls and three partial skeletons (including armor and a tail club) have been found. Ankylosaur trackways have been found near Sucre, Bolivia, South America.