Category: Dinosaur

Ankylosaurus (an-kie-lo-sore-us) means literally ‘fused (or stiff) lizard,’ referring to its thick, short, inflexible body. It is the ‘archetypal’ representative of the Ankylosauridae, a family of armored quadrupedal dinosaur that inhabited the Late Cretaceous of both North America and Asia. Together with the duckbill Edmontosaurus, horned dinosaur Triceratops, and the theropod Tyrannosaurus, Ankylosaurus lived in the latest Cretaceous Period and so was amongst the last dinosaurs to have existed in North America before the great extinction event at the end of the Cretaceous.



Genera and Species

Classification: Thyreophora, Ankylosauridae

Species: Ankylosaurus magniventris (referring to its broad belly)


Ankylosaurus had a low, broad body with almost turtle-like or armadillo-like proportions and a wide, flattened head with two pairs of horn-like structures projecting from the back. The front of the jaws bore a beak, and the rest of the jaws contain rows of small leaf-shaped teeth. Large plates called osteoderms are embedded in the skin of the body, and half rings of bone are embedded in the skin of the neck. These bony elements tended to fused together, making the body very stiff. The tail ends in a massive bony club.


Length: 6.25 m (20.5 feet)

Weight: 6 tons.


Ankylosaurus, with its flattened broad body and short legs, probably could not have reached anything but ground-dwelling plants, using its beak to crop and its rows of small, leaf-shaped teeth to cut the vegetable matter up before swallowing. The structure of the mouth and teeth suggest that it was a generalist, feeding on a variety of vegetation. It must have been a slow moving animal, and certainly could not have outrun predators. However, the osteoderms provided good protection for the internal organs, and the heavy tail club could certainly have inflicted serious damage if it was swung sideways into a predator’s leg, so escape from a predator wasn’t really necessary.

History of Discovery

The first Ankylosaurus specimen was collected in 1906 by Peter Kaisen during an expedition of the American Museum of Natural History to what is now Montana, and described and named by the famous dinosaur hunter Barnum Brown in 1908. Curiously, although Ankylosaurus is a very familiar dinosaur, only three skulls and a few partial postcranial skeletons have ever been found. Fortunately, this is enough to give us a pretty good idea what the whole animal looked like.


Ankylosaurus lived on the coastal plain between the shores of the Western Interior Seaway, which covered much of central North America at the time, and the newly formed Rocky Mountains to the west. The climate was temperate to subtropical with abundant water. Plant life, including forests, was diverse.


  1. Paul, G. (2010). The Princeton Field Guide to Dinosaurs (pp. 5534). Princeton, New Jersey: University Press Princeton.

  2. Worth, G. (1999). The Dinosaur Encyclopaedia Dev13 (pp. 340). Scarborough, Western Australia: HyperWorks Reference Software.