Ankylosaurus: Armored Cretaceous Herbivore

Ankylosaurus was a genus of herbivorous dinosaur that lived during the late Cretaceous Period, dying out during the Cretaceous-Tertiary Extinction. It was a large, short dinosaur between 25 and 35 feet long and 6 feet wide with hind legs longer than its forelegs. Ankylosaurus represents the last and the largest group of ankylosaurids at the end of the Cretaceous Period and lived in North America. Fossils of the dinosaur have been unearthed primarily in deposits in Montana and Canada.

The most striking feature of ankylosaurus was its armor. Large, bony knobs were embedded in the skin of its back, legs, and head, which would have made it difficult, if not impossible for predators to penetrate. Today, certain reptiles like crocodiles and certain mammals like armadillos contain these specialized bony projections called osteoderms underneath their skin. In addition to this already potent defense mechanism, ankylosaurus also sported a bony club the size of a basketball at the end of its long tail. This heavy weight could have been swung with tremendous force at attackers, with enough power to shatter bone. It is these adaptations which would make ankylosaurus quite successful in the Cretaceous. After the Cretaceous-Tertiary Extinction, some mammals would adopt similar measures to carve out a niche for themselves. Mammalian glyptodonts of South America developed a dome-shaped mass of bone on their backs to protect themselves in a similar fashion.

Ankylosaurus was herbivorous, feeding on small ferns, shrubs, and low-hanging vegetation. Its mouth had several rows of leaf-shaped teeth which would have been well-suited for grinding up this vegetation. Up until this point, other families of dinosaurs like stegosaurs had been the dominant low-browsing herbivores. However, by the late Cretaceous, ankylosaurids were starting to replace them in this particular niche. Because of the size of its brain cavity and the presence of an elaborate system of structural defenses, it likely had a small brain-to-body ratio and was not especially smart. However, this is indicative of many dinosaur herbivores which merely needed to know how to eat and to run from danger. Fossilized footprints found in South America reveal that ankylosaurus was not a lumbering beast but could move along at a bit of a jog-something quite impressive for such a short, heavy dinosaur.

Ankylosaurus, along with other well-known dinosaurs like Tyrannosaurus Rex and triceratops met its end during the mass extinction event at the end of the Cretaceous period. Though the mightiest of the ankylosaurids, this tank-like beast was one of the last of one of the greatest animal dynasties on earth.