Stegosaurus | Facts & Information

The dinosaur Stegosaurus lived in the Mesozoic era, in the Upper Jurassic, 145 million years ago. Because of its bony shell on the dorsal side it was called”the dinosaur with the roof on its back".

This animal with armor became the emblem of the US State of Colorado. Over the years he was the most studied and largest of the group of dinosaurs with armor, being considered a follower of the first sauropods. Stegosaurus is easily recognized from all prehistoric creatures precisely by the presence on the dorsal side of two strings of very large bone plates.

These plates are shaped like huge arrowheads, arranged along the spine, starting from the head area to the tip of the tail. Some of these boards were up to 30 cm in width. Also on the tip of the tail there were two pairs of thick, very sharp spines, which were about 1 m long.

The skeleton of a beautiful specimen was reconstructed at the Natural History Museum in Denver-Colorado. But when it was found it did not have the huge bone plates attached to the skeleton. That is why some paleontologists have considered that there is a possibility that these plates were simply implanted in the skin, to defend as a shield the back of the animal.

There is also the possibility that they were positioned vertically, alone or in pairs. The length of this dinosaur was estimated at 7-9 meters, height at 4 meters, and weight at about 2 tons.

This thorny Ridge would appear to have been covered with a hard substance just like the horns of today's cattle. Other researchers have hypothesized that these plaques may have been covered with a membrane rich in blood vessels – through which the dinosaur controls its body temperature with the environment, just as it does with the ears in elephants. In this case the arrangement of the plates on the back of the animal would have been zigzag, alternating. The heat would have been absorbed very quickly by the immense irrigation of the plates with blood, and when exposed to the wind, the movement of the plates caused a loss of heat.

The forelimbs were small and short, so when the animal moved on all fours it had to keep its head close to the ground. The paws of the front limbs were massive, they had heavier and longer hooves than those of the hind paws. The hind limbs were longer and more muscular.

The head was quite small, 40 cm long, had a sharp muzzle with a horny beak and jaws with teeth. The cranial box housed a very small brain that weighed only 60 grams. Following research, paleontologist Othniel Charles Marsh concluded that the Stegosaurus had the smallest brain of all the herbivorous dinosaurs discovered.

The researchers also observed a cavity in the spine, about above the hind limbs, and deduced that this space would have housed a tissue that had the role of a second brain. This tissue would have received certain stimuli (from the posterior region of the body) through which it would have coordinated the movements of the hind limbs. There is also the possibility that this cavity also harbors a glycogen – producing gland-a substance that would have added energy to the hind limbs in case of danger.

The skull of this dinosaur showed that the jaws and masticatory muscles were not very developed, the front teeth were missing, it had only triangular and small teeth, and the polished teeth were positioned in the posterior part of the mouth, which led paleontologists to conclude that the giant Stegosaurus was a herbivorous animal, which fed on various plants and tender leaves and lived in wooded areas.

With his small snout he tore mostly small plants off the ground and used to swallow stomach stones – gastroliths – to tear the plant food out of his stomach, and when they rounded up they were regurgitated and replaced with new ones with straighter edges.

When attacked by predatory dinosaurs, the Stegosaurus defends itself with the help of its tail or points its armor with bone plates to protect its vulnerable sides. The Thorns at the tip of the tail were similar to the horns of today's Bulls and served as an attack weapon, by rotating the tail managing to put all the attackers on the run.

With this armor on his back, heavy legs and massive body with curved backs it is clear that this dinosaur was not a fast runner. They were best defended when they were in flocks and acted together against predators.

During the mating season these dinosaurs showed their availability by coloring the plates – which changed their hue due to the strong vascularization inside them.

Also, the plates were a means of communication with other dinosaurs that were part of the herd. When one of the individuals notices a possible danger they signal their anxiety by changing the color of these plaques.

The Stegosaurus dinosaur belongs to the order Ornithischia and the family Stegosauridae. There are several species that are part of this family, such as: Stegosaurus armatus (the first species discovered, had relatively small plates and measured in length 9 meters), Stegosaurus longispinus (species discovered in Wyoming-USA, measure in length 7 m) and Stegosaurus stenops (species discovered in Colorado in 1887, had wider and larger plates, measure in length 7 m).