an·ky·lo·saur (ăng'kə-lō-sôr') pronunciation or an·ky·lo·sau·rus (ăng'kə-lō-sôr'əs)

A large herbivorous dinosaur of the Cretaceous Period, having a squat, heavily armored body and a clubbed tail.

[New Latin Ankylosaurus, genus name : Greek ankulos, crooked, bent + Greek sauros, lizard.]


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Ankylosaurus (ăn'kələsôr'əs) , [Gr.,=crooked lizard], genus of heavily armored, herbivorous quadripedal dinosaurs, the best known of which is the species A. magniventris, the largest and heaviest of the ankylosaurs. Sturdy and built low to the ground, the largest ankylosaurs are estimated to have been 33 ft (10 m) from head to tail. Ankylosaurus was covered by tough, rounded bony plates that were keeled, like the bottom of an overturned boat. Bony plates were also embedded in the upper eyelids. The dinosaur was characterized by a large club of fused plates that it carried aloft at the end of the tail. The vertebrae of the end of the tail were fused to support the club, which is thought to have been used in defense. Like other ornithischian dinosaurs, ankylosaurus was beaked. It also had small teeth toward the back of the jaws and an intricate system of nasal sinuses, the purpose of which is unclear. Ankylosaurus flourished in the late Cretaceous period. Specimens have been found in Montana, Wyoming, and in the Red Deer River area of Alberta, Canada.

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The noun ankylosaur has one meaning:

Meaning #1: having the back covered with thick bony plates; thought to have walked with a sprawling gait resembling a lizard's
Synonym: ankylosaurus

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Conservation status: Fossil
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Archosauria
Superorder: Dinosauria
Order: Ornithischia
Suborder: Ankylosauria
Family: Ankylosauridae
Genus: Ankylosaurus


A. magniventris

Ankylosaurus was the last, largest, and most famous of the armored dinosaurs known as the ankylosaurians. Its back and sides were covered with a stiff shell of armor, but its underbelly was exposed. It also had a great club-like tail that could be used for defense against predators. Ankylosaurus was about the size of an elephant, but had a low-slung, very wide body.


Ankylosaurs weighed up to 4.5 metric tons (5 tons), and were about 10 meters (30 feet) long. While they were 1.8 meters (6 feet) wide, there were only 1.2 meters (4 feet) tall. Its legs were short, with the rear legs longer than the forelegs. It had five toes on each foot. The flat, triangular skull was thick, meaning the brain was quite small.

The flexible skin of an ankylosaur was covered with thick, hard ovals of embedded bone, which superficially resembled the plates of an armadillo. The armor completely covered the entire surface of its head and exposed body; it even had bony shelves over its eyes.

Ankylosaurus also had short spikes lining both sides of its body. A set of horns stuck out from the back of its head, the two largest protruding from the corners. Unlike the Stegosaurus, the armor of the Ankylosaurus was attached directly to its skeleton, instead of being attached to its skin.

It also had a bony club on its tail which it could swing from side to side. The tail was muscular, so it probably made an excellent weapon when used for defense. The tail was made from hardened tissue, fused to the tail bones (caudal vertebrae).


Ankylosaurus existed between 65 and 70 million years ago, in the Maastrichian age of the Late Cretaceous period, and was one of the last dinosaurs before they were wiped out by the Cretaceous-Tertiary extinction event.

They were plant-eaters (herbivores). Being stiff and low-slung, they must have grazed on low-lying vegetation.

Even giant carnivores of the Maastrichian, like Tyrannosaurus, Deinonychus, and Tarbosaurus, probably could not break through ankylosaur armor. It is believed they would lie flat on the ground, hiding their soft stomach from attackers. Like a porcupine, they were only vulnerable when flipped over, which was made more difficult by the row of short spikes running down their sides.

Classification and history

The only species in the genera, Ankylosaurus magniventris, was named by Barnum Brown in 1908. Fossiled remains have been found in Alberta, Canada, as well as in Wyoming and Montana in the United States. Euoplocephalus was originally believed to be an ankylosaur, but it now has its own genera.

The remains are fairly complete, including a couple skulls and the signature tail. A trackway of an ankylosaur was found in Sucre, Bolivia in 1996, which showed that the massive dinosaur could move fairly quickly.


The name Ankylosaurus is derived from the Greek agkylos, meaning "bent" or "crooked", and sauros, meaning "lizard". This refers to the way the bony plates on its back have fused with the thick skin, and the way many of the internal supporting structures like the backbone (vertebrae) and ribs have also fused together.

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Ankylosaurus".
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