Ankylosaurus

Ankylosaurus dinosaur belongs to a genus of armored dinosaurs. Its fossil records have been found in the geological formations about 68 to 66 million years ago from the Cretaceous Period in western North America. It was named by Barnum Brown and the genus name means “fused lizard”. It belongs to the family Ankylosauridae. It is thought that these are slow-moving animals thus whenever it is required they can make quick movements. It has a broad muzzle. Sinuses and nasal chambers that are present in the snout may have been to balance the heat and water or they may have played a role in the process of vocalization. The tail club is used for defense against their predators or in intraspecific combat. Ankylosaurus has been found in the regions of Scollard, Frenchman, and Ferris formations. Their ranges and the ecological niches do not appear as overlapped, and the Ankylosaurus genus may have inhabited the upland areas. Ankylosaurus genus also lived alongside the dinosaurs such as Triceratops, Tyrannosaurus, and Edmontosaurus.

Brown considered that the Ankylosaurus dinosaur so distinct that he made it a type of genus of a new family, Ankylosauridae. These are specified by triangular skulls, short necks, stiff backs, osteoderms, and broad bodies. He also classified the genus Palaeoscincus and Euoplocephalus as a part of the family. For comparison only a few specifications were present in their incomplete members of the family, he believed that a group was part of the suborder Stegosauria. In the year 1923 Osborn coined the term Ankylosauria, thereby placing the ankylosaurids in their own suborder. Ankylosaurus was the largest-known Ankylosaurine dinosaur and it was possibly the largest ankylosaurid. In the year 2004 Carpenter estimated that the individual Ankylosaurus with the largest-known skull.

[Image will be Uploaded Soon]

Ankylosaurus Dinosaur - History

In 1906, an American paleontologist Barnum Brown in the American Museum of Natural History expedition discovered an Ankylosaurus magniventris. This specimen that was discovered consisted of the upper part of a skull, a pair of teeth, part of the shoulder girdle, ribs, more than thirty osteoderms called armor plates, and dorsal, cervical, and caudal vertebrae. Brown scientifically described the animal in the year 1908 where the genus name was derived from the Greek words ankulos which means 'bent' or 'crooked'. The name can be translated as “fused lizard”, “stiff lizard”, or “curved lizard”. The species name magniventris is derived from the Latin word Magnus and venter, which refers to the great width of the body of the animal.

Many of the traditional depictions which are popular show that the Ankylosaurus in a squatting posture and with a huge tail club being dragged over the ground. Modern reconstructions show that this animal has a more upright limb posture and a tail that is held off the ground. Likewise, there are large spines that are projecting from the body similar to those of nodosaurid ankylosaurs. The armor of Ankylosaurus has been conflated with that of Edmontonia, which was earlier referred to as Palaeoscincus. In addition to this Ankylosaurus has being depicted with spikes.

Ankylosaurus Dinosaur - Description

Paleoenvironment: Ankylosaurus dinosaurs lived on the plains of the coastal regions in between the shores of the Western Interior Seaway. This covered most of central North America at that time and the newly formed Rocky Mountains to the western part. The suitable climate for sustainability was temperate to subtropical with an abundant amount of water. Plantlife includes forests which were diverse in nature.

Skull: The three known skulls of Ankylosaurus differ in various details. The skull was triangular in shape, and it is low and wider. The backside of the skull was broader and low. At the region of premaxillae, the skull had a broad beak. The orbits or the eye sockets were almost round to slightly oval in shape and they don’t face directly sideways because the skull was tapered towards the front. As in the other ankylosaurines, the braincase was short and robust. Crests that are present above the orbits are merged into the upper squamosal horns, which are pointed back from the skull to the sides of the skull. Below the location of the upper horns, the jugal horns were present, which are pointed backward and down. The horns that may have originally been considered as the osteoderms are fused into the skull. The cranial ornamentation which is scale-like in nature is found on the surfaces of the Ankylosaurs skulls, it is called "caputegulae". These scale-like ornamentations destroy the sutures that are present in between the skull elements, which is found common for adult ankylosaurs. The caputegulum pattern of the skull was variable in between the specimens. The caputegulae pattern is named according to their position found on the skull. Ankylosaurus dinosaurs include comparatively large, hexagonal, or diamond-shaped nasal caputegulum at the front of the snout. It was found in between the nostrils, which consists of loreal caputegulum on each side. Above each orbit, it consists of an anterior and posterior supraorbital caputegulum, and a ridge of nuchal caputegulae present at the back of the skull.

Postcranial Skeleton: The structure of most of the skeletons of Ankylosaurus, including the tail, pelvis, and feet, is still unknown. It was a quadrupedal and its hind limbs were found longer than its forelimbs. In the holotype specimen, the scapula measures about 61.5 cm in length and it was fused with the coracoid which is a rectangular bone that is connected to the lower end of the scapula. It also had connective tissue for various types of muscle attachments.

The cervical vertebrae consist of broad neural spines which were increased in height towards the body. The front part of the neural spines had well-developed connective tissue or entheses, which was common among adult dinosaurs, and it indicates the presence of the indicating massive head. The neural spines had ossified tendons, which also found overlapped in some of the vertebrae. The ribs of the back vertebrae especially the last four were fused to form diapophyses and parapophyses and in this part of the body, the ribcage was found very broad.

Armor: A prominent feature of the Ankylosaurus dinosaur was its armor, it consists of knobs and plates of bone which are known as osteoderms or scutes, these are found embedded in the skin. Since these have not been found in the articulation, their exact placement on the body is still unknown. The osteoderms ranged from one centimeter in diameter to 35.5 cm in length and varied in shape. The osteoderms of Ankylosaurus were generally thin-walled and hollowed on the underside. Many smaller osteoderms and ossicles have probably occupied the space that is present in between the larger ones. The osteoderms that cover the body are very flat, even though with a low keel at one margin. Ankylosaurus had smaller osteoderms along with a keel that is found across the midline.

Limb Movements: Reconstructions of the musculature of the forelimbs of ankylosaur which was made by Coombs in the year 1978 suggest that the forelimbs bore the majority of the weight of the animal. These were adapted for the high force delivery on the front side of the feet, possibly for the purpose of food gathering. In addition to this Coombs also suggested that these may have been capable diggers, even though the hoof-like structures found on the manus would have limited the fossorial activity. Ankylosaurs were likely to have been slow-moving and sluggish animals, even though they may have been capable of making quick movements whenever necessary.

Growth: The largest Ankylosaurus specimen squamosal horns are blunter than those of the smallest specimen, which is also the case in Euoplocephalus, which may represent ontogenetic variation. The forelimbs have strongly increased in a good condition while the hindlimbs relative to the rest of the skeleton didn’t become larger. The underlying bone band in the cervical half-rings are developed as outgrowths that connecting them with the underlying osteoderms. These simultaneously fused to each other. On the skull at the snout and the rear rim region, the middle bone plates first get ossified, with the process of ossification these gradually extend towards the middle regions. On the rest of the body, ossification progressed from the neck backward in the direction of the tail.

Defense: The osteoderms that were found on the ankylosaurids were thin when compared to those of other ankylosaurs, and they appear to have strengthened by cushions of the collagen fibers that are distributed randomly. The ankylosaurids with armor thus provided with covering that was both lightweight and highly durable in nature. It was being resistant to the breakage and penetration of the ostederms by the teeth of predators. The palpebral bones present over the eyes may have been provided the additional protection for them. Carpenter suggested in 1982 that the heavily vascularized armor may also have had a role in thermoregulation as in modern crocodilians.

The tail club of the Ankylosaurus seems to have been as an active defensive weapon that is capable of producing enough amount of impact to break the bones of an assailant. The tendons of the tail club were partially ossified and they were not very elastic, allowing great force to be transmitted to the club when it was used as a weapon. Coombs suggested in 1979 that several hindlimb muscles would have controlled the swinging of the tail, and that violent thrusts of the club would have been able to break the metatarsal bones of large theropods. The study also found that while adult ankylosaurid tail clubs were capable of breaking bones, those of juveniles were not.