Stegosaurus lived in the Mezozoic era, in Jurassic, 145 million years ago. Due to its dorsal bone carcass, it was called “the dinosaur with the roof in the back”.
The fossil remains of these dinosaurs were discovered in 1877 by the great American paleontologist Othniel Charles Marsh in regions where these prehistoric animals used to travel once and where Montana, Colorado, Wyoming, Utah, Oklahoma are now.
This armored animal has become the emblem of the American state of Colorado. Over the years he was the most studied and the largest in the group of dinosaurs with armor, being considered a descendant of the first stegosaurus. Stegosaurus is readily recognizable from all prehistoric creatures by the presence on the dorsal side of two very large bones.
These plates have the shape of huge arrowheads along the spine, starting from the head to the tip of the tail. Some of these plates were up to 30 cm in width. Also on the tip of the tail there were two pairs of thick, very sharp spikes, which were about 1 m long.
The skeleton of a beautiful copy was reconstituted at the Denver-Colorado Natural History Museum. But when it was found, it did not present the huge skeleton plates. That’s why some paleontologists thought there was a possibility that these plates were simply implanted into the skin to defend themselves as a shield behind the animal.
There is also the possibility that they have been positioned vertically, alone or in pairs. The length of this dinosaur was estimated at 7-9 meters, the height at 4 meters, and the weight at about 2 tonnes.
This spiny crest would seem to be covered with a hard substance just like the present horns of the cattle. Other researchers have hypothesized that these plates would have been covered with a very rich membrane in blood vessels – by which the dinosaur controlled its body temperature with the environment, just as it did with the ears on the elephants. In this case, the layout of the plates on the back of the animal would have been zigzag, alternately. The heat would have been absorbed very quickly by the immense irrigation of the blood plaques, and when exposed to the wind, the movement of the plates caused a loss of heat.
The previous limbs were small and short, so when the animal moved on the four paws it had to keep its head close to the ground. The forelegs of the front limbs were massive, with holes that were heavier and longer than those of the hind paws. The posterior members were longer and more muscular.
The head was small enough, 40 cm long, had a sharp knife with a crown and a tooth jaw. The cranial box housed a very small brain, weighing only 60 grams. Following research, paleontologist Othniel Charles Marsh concluded that Stegosaurus had the smallest brain out of all herbivorous dinosaurs discovered.
The researchers also observed a cavity in the spine, slightly above the posterior limbs, and deduced that this space would have housed a brain that had the role of a second brain. This tissue would have received some stimuli (in the posterior region of the body) by which it would coordinate the movements of the limbs in the back. There is also the possibility that this cavity also shelters a glycogen-producing gland – the substance that would give the posterior limbs more energy in case of danger.
The skull of this dinosaur showed that the maxillary and masticatory muscles were not very developed, the front teeth were missing, had only triangular and small teeth, and the polished masses were positioned in the posterior part of the mouth, which led the paleontologists to conclude that the giant Stegosaurus was a animal herbivor, feeding on different plants and leafy leaves and living in wooded areas.
With his little snout, he mostly broke the small plants on the ground and used to swallow stomach stones to break up their vegetal food from the stomach, and when they were rounded they were regurgitated and replaced with new ones, straight.
When attacked by predatory dinosaurs, the Stegosaurus defenses with his tail or turns his armored bones armor to protect his vulnerable sides. The tails at the tip of the tail were similar to the present-day bull’s horns and served as the weapon of attack by rotation of the tail that managed to escape all the attackers.
Having this armor on his back, his heavy legs, and his massive curved spine, it is clear that this dinosaur was not a fast runner. They best appeared when they were flocking and acting together against the predators.
During the mating season, these dinosaurs showed their availability through the color of the tiles – which changed their nuances due to the strong vascularity inside them.
Plates were also a means of communicating with other dinosaurs that were part of the herd. When one of the individuals noticed a possible danger, they reported their anxiety by changing the color of these plates.
The Stegosaurus is part of the Order of Ornithischia and the Stegosauridae family. There are several species of this family, such as Stegosaurus armatus (the first species found, had relatively small plates and a length of 9 meters), Stegosaurus longispinus (species found in Wyoming, USA, measuring 7 meters long) and Stegosaurus stenops (species discovered in Colorado in 1887, had larger and larger plates, measuring 7 m in length).