Facts About Ankylosaurus, the Armored Dinosaur

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How Much Do You Know About Ankylosaurus?

Ankylosaurus was the Cretaceous equivalent of a Sherman tank: low-slung, slow-moving, and covered with thick, nearly impenetrable armor. On the following slides, you'll discover 10 fascinating Ankylosaurus facts.

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There Are Two Ways to Pronounce Ankylosaurus

Possible appearance of a Ankylosaurus according to the few bones found. Based on skeletal reconstruction in Carpenter 2004 and photographs of fossils.
Mariana Ruiz Villarreal (LadyofHats)/Wikimedia Commons

Technically, Ankylosaurus (Greek for "fused lizard" or "stiffened lizard") should be pronounced with the accent on the second syllable: ank-EYE-low-SORE-us. However, most people (including most paleontologists) find it easier on the palate to put the stress on the first syllable: ANK-ill-oh-SORE-us. Either way is fine--this dinosaur won't mind, as it has been extinct for 65 million years.

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The Skin of Ankylosaurus Was Covered with Osteoderms

Osteoderm of Ankylosaurus specimen AMNH 5895 in outer and inner view.
Barnum Brown/Wikimedia Commons

The most notable feature of Ankylosaurus was the tough, knobby armor covering its head, neck, back, and tail--pretty much everything except its soft underbelly. This armor was made up of densely packed osteoderms, or "scutes," deeply embedded plates of bone (which weren't directly connected to the rest of Ankylosaurus' skeleton) covered by a thick layer of keratin, the same protein as is contained in human hair and rhinoceros horns.

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Ankylosaurus Kept Predators at Bay with its Clubbed Tail

Reconstructed Scolosaurus thronus skeleton (based on holotype ROM 1930, formerly assigned to Euoplocephalus), an extinct ankylosaur- Took the photo at Senckenberg Museum of Frankfurt (19 August 2011).
Ghedoghedo/Wikimedia Commons

The armor of Ankylosaurus wasn't strictly defensive in nature; this dinosaur also wielded a heavy, blunt, dangerous-looking club on the end of its stiff tail, which it could whip at reasonably high speeds. What's unclear is whether Ankylosaurus swung its tail to keep raptors and tyrannosaurs at bay, or if this was a sexually selected characteristic--that is, males with bigger tail clubs had the opportunity to mate with more females.

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The Brain of Ankylosaurus Was Unusually Small

An Ankylosaurus head (cast of specimen AMNH 5214), on display at the Museum of the Rockies in Bozeman, Montana. This is from a specimen collected in Custer County, Montana.
Tim Evanson/Wikimedia Commons

As imposing as it was, Ankylosaurus was powered by an unusually small brain--which was about the same walnut-like size as that of its close cousin Stegosaurus, long considered to be the most dim-witted of all the dinosaurs. As a rule, slow, armored, plant-munching animals don't require much in the way of gray matter, especially when their main defensive strategy consists of flopping down on the ground and lying motionless (and perhaps swinging their clubbed tails).

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A Full-Grown Ankylosaurus Was Immune from Predation

Ankylosaurus, DinoPark Vyškov.
DinoTeam/Wikimedia Commons

When fully grown, an adult Ankylosaurus weighed as much as three or four tons and was built close to the ground, with a low center of gravity. Even a desperately hungry Tyrannosaurus Rex (which weighed more than twice as much) would have found it nearly impossible to tip over a full-grown Ankylosaurus and take a bite out of its soft belly--which is why late Cretaceous theropods preferred to prey on less-well-defended Ankylosaurus hatchlings and juveniles.

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Ankylosaurus Was a Close Relative of Euoplocephalus

Royal Alberta Museum -- Ankylosaurus.
jasonwoodhead23/Wikimedia Commons

As armored dinosaurs go, Ankylosaurus is much less well-attested than Euoplocephalus, a slightly smaller (but more heavily armored) North American ankylosaur that's represented by dozens of fossil remains, down to this dinosaur's scute-covered eyelids. But because Ankylosaurus was discovered first--and because Euoplocephalus is a mouthful to pronounce and spell--guess which dinosaur is more familiar to the general public?

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Ankylosaurus Lived in a Near-Tropical Climate

World Map indicating global tropic and sub-tropic regions.
KVDP/Wikimedia Commons

During the late Cretaceous period, 65 million years ago, the western United States enjoyed a warm, humid, near-tropical climate. Considering its size and the environment it lived in, it's extremely likely that Ankylosaurus possessed a cold-blooded (or at the very least homeothermic, i.e., self-regulating) metabolism, which would have allowed it soak up energy during the day and dissipate it slowly at night. However, there's virtually no chance that it was warm-blooded, like the theropod dinosaurs that tried to eat it for lunch.

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Ankylosaurus Was Once Known as "Dynamosaurus"

The "type specimen" of Ankylosaurus was discovered by the famous fossil hunter (and P.T. Barnum namesake) Barnum Brown in 1906, in Montana's Hell Creek formation. Brown went on to unearth numerous other Ankylosaurus remains, including scattered pieces of fossilized armor that he initially attributed to a dinosaur he dubbed "Dynamosaurus" (a name that has unfortunately vanished from the paleontological archives).

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Dinosaurs Like Ankylosaurus Lived All Over the World

Ankylosaurus has lent its name to a widespread family of armored, small-brained, plant-eating dinosaurs, the ankylosaurs, which have been discovered on every continent except Africa. The evolutionary relationships of these armored dinosaurs is a matter of dispute, beyond the fact that ankylosaurs were closely related to stegosaurs; it's possible that at least some of their surface similarities can be chalked up to convergent evolution.

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Ankylosaurus Survived to the Cusp of the K/T Extinction

Planetoid crashing to primordial Earth.
Don Davis/NASA

The near-impenetrable armor of Ankylosaurus, combined with its presumed cold-blooded metabolism, enabled it to weather the K/T Extinction Event better than most dinosaurs. Even still, scattered Ankylosaurus populations slowly but surely died out 65 million years ago, doomed by the disappearance of the trees and ferns they were accustomed to munching on as vast clouds of dust circled the earth in the wake of the Yucatan meteor impact.

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Strauss, Bob. "Facts About Ankylosaurus, the Armored Dinosaur." ThoughtCo, Apr. 5, 2023, thoughtco.com/things-to-know-ankylosaurus-1093772. Strauss, Bob. (2023, April 5). Facts About Ankylosaurus, the Armored Dinosaur. Retrieved from https://www.thoughtco.com/things-to-know-ankylosaurus-1093772 Strauss, Bob. "Facts About Ankylosaurus, the Armored Dinosaur." ThoughtCo. https://www.thoughtco.com/things-to-know-ankylosaurus-1093772 (accessed March 28, 2025).