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Ankylosaurus facts: an armored giant dinosaur with a club-like tail

66 million years ago, the world was different and one of the most protected animals, if not the most, in the history of our planet roamed the rainforests of North America, sniffing for food. The dinosaur was covered from head to toe in bony armor. And probably even Tyrannosaurus Rex himself feared and bypassed him, so as not to anger the living tank. And it is quite reasonable, because Ankylosaurus was a giant and had a bone-crushing weapon on the end of its tail. But it also had an Achilles’ heel. Here are the facts about this dinosaur.

When was Ankylosaurus first discovered

A team led by Brown discovered the archetypal member of the Ankylosauria group, A. magniventris (AMNH 5895), in the Hell Creek Formation, Montana, in 1906. It consisted of the upper part of the skull, as well as vertebrae, ribs, a fragment of the shoulder girdle, and a fragment of the shell.

The name Ankylosaurus means a bent lizard. The animal got its name from the American paleontologist Barnum Brown, in 1908. The generic name comes from the Greek ἀγκύλος (ankulos) “bent”, referring to the medical term ankylosis and σαῦρος (sauros) “lizard”.

The type species is A. magniventris; the species name is derived from the Latin words magnus, “great”, and venter, “belly”, referring to the great width of the animal’s body.


Ankylosaurus is a plant-eating, armored dinosaur that belongs to the class of reptiles, the clade of archosaurs, and the order of ornithischia.

Ankylosaurus is an extinct genus of the Dinosauria clade, family Ankylosauridae. The genus is monotypic, as it includes only one species known as Ankylosaurus magniventris.

Despite the fact that no whole skeleton of ankylosaurus has been found so far, and the fact that related dinosaurs are better studied, it is ankylosaurus that is considered the archetypal representative of armored dinosaurs.

Other ankylosaurs had similar features: a body covered with strong, heavy armor and a massive thickening, a club, on the tail. However, Ankylosaurus surpasses all its relatives in size and is the largest of all known Ankylosaurs. Ankylosaurids, in turn, are part of a broader taxon (Ankylosauridae), the Ankylosauria suborder, which also includes Nodosaurids. The latter differ from Ankylosaurids in that they have no beak.

How long did Ankylosaurus exist

Ankylosaurids appeared on Earth in the middle of the Jurassic period – about 160 million years ago.

The fossil remains of Ankylosaurus have been found in geological formations dating to the most recent Cretaceous era, in the west of the North American continent. It inhabited North America about 68-66 million years ago.

Ankylosaurus disappeared along with most other dinosaur species because of the asteroid impact 66 million years ago.

Currently, there are now a total of 15 collections of Ankylosaurus remains, two of which are in museums in Canada and the remaining 13 in museums in the United States.

Ankylosaurus protective means

Ankylosaurus Description

Ankylosaurus had a very wide, stocky body. The skull of the Ankylosaurus was low, triangular in shape, and its width exceeded its length. There was an opinion that due to its massive body the Ankylosaurus was slow and clumsy, but, according to experts, this is a delusion – on the contrary, thanks to the length of its stride this reptile could move with sufficiently high speed.

From above, Ankylosaurus looked flattened and even slightly resembled a turtle. The mouth was shaped like a beak, and four small horns were located at the four “corners” of the skull, probably serving as some kind of protection against predator bites. Two rows of triangular spines may have been located at the base of the tail, one „looking” to the left and the other to the right.   


One of the most striking features of ankylosaur’s appearance is its armor, which covered the head (the jaws and even the eyelids), upper body, tail, limbs and consisted of bumps and bone plates called osteoderms. These outgrowths are not parts of its skeleton, but are bony plates growing in the mesodermal layer of the skin

Ankylosaurus bone plates were probably covered with a hard, keratinous layer. The size of the osteoderms varied from 1 to 35.5 centimeters, and they varied in shape. 

The plates formed distinct horizontal rows stretching along the animal’s neck, back, and thigh; a large number of small growths covered the unprotected space between the larger plates.

As an additional protection, there was a thorn-like thickening in the center of each such outgrowth. These organs are also characteristic of modern crocodiles, armadillos and some lizards.

The outgrowths were fused (connected) to each other in long strips, which is one of the reasons why this dinosaur is called – “fused lizard”.

Because of this unusual cover, the dinosaur is often described as a “living tank”. Only the belly of the giant dinosaur was without armor.

Osteoderms may have played a role in thermoregulation, as in modern crocodiles. In modern times, osteoderms are found not only in crocodiles, but also in armadillos and some lizards: in fact, they perform a variety of functions. Ankylosaurus plates could also perform camouflage and ceremonial functions.

Interestingly, scientists believe that each Ankylosaurus had plates on its back that formed unique patterns that could distinguish it, like a human by facial features and lines on the palms of its hands.

What color was ankylosaurus

In 2017, a study was published where scientists partially established the coloration of the species Borealopelta markmitchelli. To do this, they searched for melanin in the organic remains of a well-preserved specimen using mass spectrometry. According to the results, the relative of the ankylosaurus weighing about 1300 kg had a camouflaging coloration.

Scientists believe that Ankylosaurs had inconspicuous coloration, which allowed them to camouflage themselves in the shady bushes and not attract the attention of carnivorous reptiles. Predators may have passed by without noticing the Ankylosaurus munching peacefully on leaves.

How did the Ankylosaurus defend itself against predators

Even with teeth as sharp as knives, many predators could not bite through the ankylosaur’s bone plates. The dinosaur turned sideways toward the enemy, and it bumped into sharp spikes. And with one blow of its mace tail, the ankylosaur could knock him down, break bones and damage internal organs. With such a serious weapon, the dinosaur made it clear to the attacking predators that they were unlikely to get a meal. The Ankylosaurus could deftly manipulate the tail club, swinging it in different directions.

If the Ankylosaurus came face to face with a predator unexpectedly and could not escape, it had the opportunity to choose another strategy: pretend to be a pebble. It could lie down on its belly to protect it. Rolling over a dinosaur weighing up to several tons was no easy task.

Since Ankylosaurus had such large enemies as Tyrannosaurus and Albertosaurus as its neighbors, it had good reason to arm itself seriously.

Ankylosaurus tail club

Theropods (predatory dinosaurs), which hunted ankylosaurs, were tall and walked on two legs, so they were less stable than the short quadruped. Its legs were short but thick, giving it excellent stability. A timely and precise punch from the ankylosaur’s heavy tail club could take a predator by surprise and knock it down, inflicting serious wounds, that could cause a long and hungry death.

Scientists believe that the thickening at the end of the tail was formed from bone knots, originally covered with skin, which, as they grew, had been joined together very tightly, so that the end of the tail was very stiff. The movements of the tail was controlled by special muscles located at the base of it, usually serving to move the hind limb backwards when walking. These tendons were somewhat hardened and lacked elasticity. When swinging the tail, the ankylosaurus was able to transmit a significant force impulse to the tail club being at risk.

A 2009 study showed that adult Ankylosaurs could break bones with its tail club, but young individuals accordingly had no such ability.

Tail swinging is a very plausible behavior of ankylosaurids, but it is unknown whether the tail was used during interspecies fighting or intraspecies fighting, or both.

It has also been suggested that the tail club was a kind of “false target” for the predator, as from a distance it could be mistaken for the head. However, this hypothesis is now widely disputed.

Ankylosaurus tail club is up to 57 centimeters wide. It is about two to three times the width of a human face.

How big was an adult Ankylosaurus

In 2004, Kenneth Carpenter revised the estimated size of the reptile according to the size of the skulls found. The biggest known specimen, CMN 8880 (this skull is 64.5 cm long and 74.5 cm wide), was estimated to be 6.25 meters long, 1.5 meters wide, and 1.7 meters in height. The smallest specimen, AMNH 5214 (skull 55.5 cm long and 64.5 cm wide), reached about 5.4 m in length and 1.4 m in height from Carpenter’s perspective.

However, in 2017, a team of researchers compared Ankylosaurus to more complete ankylosaurid fossils and calculated a length of 6.02-7.95 m for specimen AMNH 5214, and 7.56-9.99 m for CMN 8880. Nevertheless, guided by the size of vertebrae, the authors note that the upper bar of the possible size range for CMN 8880 is most likely overestimated, and the most plausible length is about 8 m. Thus, Ankylosaurus could weigh as much as an adult African elephant and rhinoceros combined.

Ankylosaurus Habitat

Ankylosaurs are found in different parts of North America. A type specimen was found in the Hell Creek Formation, Montana, while other specimens were found in the Lance Formation, Wyoming, and the Scollard Formation, Canada, Alberta, all dating to the late Cretaceous period.

Ankylosaurids are thought to have appeared first in Asia. It happened at the very beginning of the Early Cretaceous Period, when Asia and North America were connected by a strip of land. Apparently, the ancestors of Ankylosaurus came from Asia to North America via this peculiar land bridge.

The above-mentioned Hell Creek, Lance, and Scollard formations represent various sections of the west coast shallow sea that separated the western and eastern parts of the North American continent during the Cretaceous.

They represented a broad coastal plain extending westward from the seaway to the newly formed Rocky Mountains. These formations consisted for the most part of sandstone and mudstone, which is the hallmark of floodplains.

The Hell Creek Formation has been most well studied for these ancient habitats. At the time of Ankylosaurus, the region was subtropical, with a warm and humid climate, with occasional rains, tropical storms and forest fires.

Many plants grew there, mostly flowering plants; conifers, ferns, and cycads were less common. The abundance of fossilized leaves, which have been found in dozens of different deposits, suggests that the area was densely overgrown with small trees.

Ankylosaurus had a broad snout, designed to feed on a variety of plants, so it probably lived in upland areas away from the coast.

What lifestyle did Ankylosaurus lead

Many species of plant-eating dinosaurs lived in herds. But scientists have not yet found mass accumulations of ankylosaur remains. Therefore, paleontologists assume that these lizards most likely lived singly.

Although the remains of several juveniles of Pinacosaurus species have been found in Mongolia, they died at the same time. It is possible that the juveniles were gathered together for protection.

A group of dead mature ankylosaurs of the species Gastonia was found in Hungary, which may indicate their age segregation.

Ankylosaurus Food

It is also known that Ankylosaurus had a bony septum between its nose and mouth, which allowed it to eat and breathe at the same time, which is inherent, for example, in humans, but is not characteristic of most modern reptiles.

Like other reptiles of its order, Ankylosaurus was a herbivore with teeth shaped like leaves. In relation to its body, the size of its teeth was smaller than those of its relatives.

The teeth of Ankylosaurus were placed deep in the mouth, and its jaws were not adapted to grind hard plant food, but its digestive system had a special design, specialized for digestion of uncut vegetation.   

However, a fish was recently found in the remains of the species Liaoningosaurus paradoxus in the area of the intestine. If this is not a simple coincidence (a fish could get into the decayed remains of a dinosaur), then this species is the first known predatory ankylosaurid.

Ankylosaurs had an excellent appetite, as evidenced by the volume of their digestive organs. It is calculated that a large Ankylosaurus, being a warm-blooded animal, must have eaten about 60 kg of vegetation per day, although most likely it could reduce this number by eating more nutritious fruits. 

The remains of Nodosaurs, the closest relatives of Ankylosaurs, were found to contain rocks that the animal swallowed to digest hard food. Ankylosaurus could do this, too.

Although the remains of the feet of this dinosaur have not yet been discovered in full, based on comparisons with other Ankylosaurs, it can be assumed that representatives of this species had five toes on each foot, equipped with claws. Thanks to them, the Ankylosaurus could easily reach the roots of trees.

Ankylosaurus’ powerful turtle-like beak helped it bite off even hard tree branches.

Ankylosaurs ate only the leaves of trees, bushes, and other greenery that they could reach to.

What Scientists Found Out by Studying Ankylosaurus’ Brain

Based on the analysis of skull fossils, experts concluded that this dinosaur had a well-developed sense of smell. Perhaps even its sense of smell was stereophonic, with each nostril catching smells from different directions. In fact, Ankylosaurus’ nose is its unique feature. The nostrils were elliptical and pointed downward and outward. In all other known ankylosaurs, they looked obliquely forward or upward.

After three years of work, scientists discovered that the ankylosaur brain mass is at least half of what would be expected based on comparisons with modern animals – about 26.5 g for a three-meter-long Bissektipelta specimen. The volume of the dinosaur brain can be compared to two walnuts.

Nevertheless, ankylosaurs survived on the planet for 100 million years, were quite successful in terms of evolution. This may have been the result of the fact that a large part of their brain was occupied by the odor recognition area. It was about 60 percent of the size of the large hemispheres. A good sense of smell helped the animal to look for food, to find relatives of the opposite sex, and to sense in time the approach of predators.

An important discovery was also made while analyzing the inner ear of the dinosaur. It turned out that the range of frequencies at which the dinosaur could hear was from 300 to 3000 hertz. This is about the same range that modern crocodiles hear. There is a rule – the larger the animals, the more low-frequency sounds they make and hear. Ankylosaurs could not hear well.

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