Ankylosaurus

Ankylosaurus is a genus of extinct herbivorous reptiles from the dinosaur superorder, the Ankylosaurid family. The genus is monotypic, as it includes only one species known to science - Ankylosaurus magniventris. Ankylosaurus fossils were found in geological formations dating from the latest epoch of the Cretaceous period (66.5-66 million years ago), in the west of the North American continent.

Despite the fact that an entire ankylosaurus skeleton has not yet been found, and despite the fact that related dinosaurs have been studied better, it is ankylosaurus that is considered to be the most typical representative of armored dinosaurs. Moreover, it is one of the most famous dinosaurs, despite such scant fossil material. Other ankylosaurids had similar features: a body covered with powerful, heavy armor, and a massive thickening on the tail. Ankylosaurus is one of the largest known ankylosaurids.Ankylosaurus by modern standards can be considered a very large animal, the size of a rhinoceros or even an adult male African elephant. According to early estimates, its length reached 7-9 or even more than 9 meters, and its mass was up to 6 tons. However, in 2004 Kenneth Carpenter revised the estimated size of the lizard in accordance with the size of the found skulls. The length of the largest known specimen, CMN 8880, was estimated at 6.25 meters, width - 1.5 meters, and hip height - 1.7 meters. The smallest specimen, AMNH 5214, from Carpenter's point of view reached about 5.4 m in length and 1.4 m in height. However, in 2017, a group of researchers compared ankylosaurus with more complete ankylosaurid fossils and calculated a length of 6.02-7.95 m for the sample AMNH 5214, 6.45—8.51 m for AMNH 5895 and 7.56—9.99 m for CMN 8880. Nevertheless, focusing on the size of the vertebrae, the authors note that the upper limit of the possible size range for CMN 8880 is most likely overstated, and the length of about 8 meters is the most plausible. Guided by the structure of the limbs, they also calculated a weight of 4.78 tons for AMNH 5214 and 7.95 tons for CMN 8880. Thus, ankylosaurus was the largest or one of the largest representatives of its family.

Ankylosaurus had a very broad, squat, stocky body. He was four-legged, the hind limbs were longer than the forelegs. Although the remains of the feet of this dinosaur have not yet been fully found, based on a comparison with other representatives of ankylosaurs, it can be assumed that representatives of this species had five toes on each foot. There was an opinion that due to the massiveness of its body, ankylosaurus was slow and unwieldy, but, according to experts, this is a misconception - on the contrary, due to the length of its stride, this reptile could move at a sufficiently high speed.

Ankylosaurus skull was low, had a triangular shape, and its width exceeded the length. Based on the analysis of the skull fossils, experts concluded that this dinosaur had a well-developed sense of smell. It is also known that there was a bone septum between the nose and mouth of ankylosaurus, which allowed it to eat and breathe at the same time, which is inherent, for example, in humans, but uncharacteristic for most modern reptiles.

Like other lizards from this group, ankylosaurus was a herbivore with teeth shaped like leaves, which were well suited for tearing vegetation. In relation to the body, the teeth of this lizard were smaller than those of its relatives. Due to the fact that it hardly needed to chew vegetation, it had no grinding devices, its teeth were located deep in the mouth and were very small and weak; the mouth had the shape of a beak, which is also characteristic of some other ankylosaurids. It is calculated that a large ankylosaur, being a warm-blooded animal, had to eat about 60 kg of vegetation per day, although most likely it could reduce this number by eating more nutritious fruits. The bones of the skull and other body parts of ankylosaurus were tightly connected to each other, which increased their strength.

One of the most striking features of the ankylosaur's appearance is its armor, consisting of massive cones and bone plates or shields, called osteoderms. They grew into the skin, and despite the fact that they were not parts of the skeleton, they played an important role in the life of the lizard. In modern times, such features are found in crocodiles, armadillos and some lizards: they perform a variety of functions.

The bone plates of ankylosaurus were probably covered with a hard, keratinized layer of keratin on top. The plates formed special horizontal rows stretching along the neck, back and thigh of the animal, even the lizard's eyelids were armored; a large number of small growths covered the unprotected space between the large plates. Smaller shields were located on the limbs and tail. Moreover, as an additional protection, there was a thickening in the form of a spike in the center of each such growth. The growths were connected to each other by long strips. In view of such an unusual dinosaur cover, it is often described as a "living tank". Previously, ankylosaur osteoderms were supposed to have mainly a protective function — only the lizard's belly remained without armor, but he could protect it by bending his legs and burrowing deep into the soil, thereby depriving the enemy of the opportunity to roll him over on his back. However, as further studies have shown, the strength of ankylosaurus osteoderms was lower than that of other ankylosaurids, and this indicates that they performed ceremonial, masking or thermoregulatory functions rather than protective. Apparently, the armor of ankylosaurs and other ankylosaurids was not an obstacle for large theropods at all, and their main method of protection from predators was camouflage.