The Stegosaurus brain was the size. Other ancient reptiles. Stegosaurus in art

They were herbivorous dinosaurs with a double row of bone plates and spines on their backs, but stegosaurs were clumsy. The plates supposedly grew from the skin, but were not connected to other bones. It is now very difficult to restore the exact location of these plates and spikes. Even about their real purpose, scientists are still arguing. They could serve both for thermoregulation of blood in the animal's body and for its protection from predators. The tail of the stegosaurus resembled a mace with its impressive size spikes.

Stegosaurus:

These lizards reached a weight of three tons and were considered the largest representatives of their family. Their body had very unusual proportions: the hind legs were much larger than the front ones, which led to the arching of the back into a huge hump. The brain, the size of a nut, was placed in a small head, which the reptiles constantly tilted down. Like other dinosaurs of this genus, the front part of the snout of stegosaurus was like a beak with teeth in the back of the jaw. On the tail were heavy spikes that could cause serious damage to the enemy. Two rows of high plates, most likely, served to scare off their rivals, and not for the sake of protection from predators. There is also an opinion that with the help of the plates, the dinosaur warmed up by exposing them to the sun, and turning them in parallel, lowered the temperature of its body. While eating, they were supposedly on four legs, however, according to a group of scientists, they could rise on two legs to reach the tops of trees.
Maximum length: 9 m
Time:
Fossil finds: Northwest America, Europe (England).

On the example of the five animals presented here (in the picture), the types of “weapons” of stegosaurs are shown. Tuoyangosaurus (2) and Stegosaurus (1) had a double row of broad, pointed dorsal plates. The plates look impressive, although many paleontologists believe that they were too thin and could not serve as protection. In Lexovisaurus (4), Ketrosaurus (5), and Dacentrurus (3), the plates were somewhat narrower and took the form of spines closer to the tail. Each of the five animals shared features common to all members of the family—elephant-like legs, arched backs, and a small, narrow head.

A unique genus, recognizable by scientists even at a distance. Why? is the accepted Latin name. But it comes from two Greek words: roof (stegos) - lizard (sauros). The animal received it due to the main distinguishing feature - the presence of a number of large leaf-shaped plates on the back. Against the background of a large body, a small head is especially contrasting.

Time and place of existence

They lived at the end of the Jurassic period about 155.7 - 145.5 million years ago. All species are found in the closer to the west of the United States (Colorado and Wyoming).

At that time, a warm, almost tropical climate prevailed there - ideal for such herbivorous dinosaurs as the Stegosaurus. The vegetation that grew on the continent, at first glance, resembled a modern rainforest, but today's plant species did not exist at that time. So, there were no flower plants. Everywhere, next to ferns and coniferous trees, ancient palm trees grew, which, in their appearance, resembled modern ones.

The drawing by Zdeněk Burian is one of the reconstructions in the habitat. There are clear footprints in the wet soil, which could have been used by predators such as Allosaurus or Ceratosaurus to detect stegosaurids.

INTERESTING INFORMATION. DO YOU KNOW THAT…

• Fossilized remains of a relative of the Stegosaurus have been found in Western Europe.
• Obviously, stegosaurs lived for a short time in the Jurassic period. The remains of these dinosaurs are found only in the upper layers of rocks.
• Some modern reptiles look like smaller versions of extinct dinosaurs.
• The lizard, which lives in Africa, has spikes on its head and body, similar to those that were in a stegosaurus. However, this lizard is 60 times smaller than a Stegosaurus, and its length reaches only 60 cm.

Types and history of discovery

Three types of stegosaurs are now considered generally recognized. The rest either did not find sufficient evidence, or were included in the main ones. Stegosaurus armatus was described by the famous professor G. Marsh in 1877. It was also one of the first officially found remains of dinosaurs in general. They were excavated north of the small American town of Morrison. Stegosaurus stenops and Stegosaurus longispinus were smaller.

body structure

The body length of this creature reached 9 meters (comparative dimensions are shown in the figure). The height is up to 4 m. The representative weighed 4.5 tons.

On the back was a whole series of plates. The discoverer of the skeleton, G. Marsh, erroneously assumed that they were connected to each other like tiles covering the back. However, it is now known that they were located perpendicular to the body of the animal. Namely, two parallel rows at some distance from each other in such a way that the sheet of one row was opposite the gap of the other. There was also a gap between the "leaves" of the stegosaurus. Really handsome - do not say anything.

The purpose of the plates is still not exactly known. The discoverers at first assumed that the plates protected it from the attacks of carnivorous dinosaurs. However, a detailed study of these by the scientific community in 1970 showed that they were fragile and did not pose any physical danger. Yes, and the attackers could easily hit the side of the body. Thus, now there are three options: defensive and two peaceful.

The first suggests that the plates were painted in bright colors (and maybe the whole Stegosaurus). Appearing in such a prickly painted form near a predator, he could scare away or at least puzzle the offender. If the second happened, then the tail came to the rescue, with which it was possible to deliver an aimed blow.

The second option - each plate was pierced by large blood vessels. This design of the circulatory system made it possible to cool the body in case of extreme heat and, conversely, quickly accumulate heat on cold mornings. After all, the Stegosaurus was a cold-blooded reptile.

The third case - the shape and color of the plates may have played a significant role in building relationships in a group of animals. Moreover, they could be used by males in mating games. There is also Robert Becker's suggestion that stegosaurus could even move bone decorations up and down. Such nine-meter peacocks moving the plates and filling them with blood more than compensate for grace with assertiveness. In fact, all three assumptions could be true - it was a universal tool.

Separately, it is worth mentioning the tail. At the end of it, sharp spikes were attached, which, unlike plates, could cause significant damage to a careless predator. The blow of a powerful tail was able to stun and leave even a mortal wound.

Stegosaurus skeleton

The photo shows museum exhibits of the species Stegosaurus stenops.

Skull on close examination of the same species.

The head was small, especially considering the enormous body of the dinosaur. The skull did not exceed 40 cm in length.
The brain also did not differ in large sizes - the size of a walnut.
Due to underdeveloped jaws, only tender leaves had to be eaten.

Appointment of plates and tail spikes

So it has not yet been clarified exactly why these ancient ornithischians needed plates. The theory put forward in early times that plates of stegosaurus served as protection when attacked from above, it did not stand up to criticism, since the horn plates were very fragile, and in no way resembled defensive shields. It was not difficult for predators such as allosaurs to gnaw them, not to mention tyrannosaurs and other giant predatory theropods. In addition, in a collision with them, no special damage could be inflicted, since they were sometimes so blunt that they not only could not cut through the rough cellular skin of predators, but, on the contrary, they themselves could be injured from a strong blow to them.

Some have suggested that predators, in view of their narrow mind, like real dogs, bite their teeth into everything that sticks out and into everything that is convenient to cling to. These very features were possessed by the dorsal plates of stegosaurus. While allosaurs and other predators ruffled their plates, the animal itself, spreading its limbs widely, led the defense with its spike-like tail, and after the defeat of one or several aggressive individuals, the predators allegedly simply retreated without causing any tangible damage to the stegosaurus.

Another assumption of scientists is based on the fact that plates were needed by stegosaurus for thermoregulation. It is possible that these porous horn formations could be completely saturated with a frequent network of small blood vessels, and thus perfectly suited to cool the body in extreme heat according to the principle of elephant or hare ears.

The fact that stegosaurs could quite effectively defend themselves and deliver lethal blows with their powerful spiked tail is evidenced by excavations. A considerable number of the same allosaurs with holes in the body have already been found, one to one suitable for the size and other parameters of the tail spikes of stegosaurus.

Nutrition and lifestyle

Stegosaurs cut low vegetation with adapted teeth. However, there are suggestions that grass and shrubs were not the only food. The dinosaur's hind limbs were much larger than its front limbs, so there is a possibility that it could stand on them (for a short time) to pluck the lower branches of trees.

It is a symbol of the American state of Colorado, where it was first excavated in the 19th century by the pioneers of paleontology.

In culture

• The stegosaurus appeared in Jurassic Park 2: The Lost World, then there was a small scene with a stegosaurus in the background in Jurassic Park 3.
• In the computer game ParaWorld, a stegosaurus either roams lava-scorched glades and savannahs, or transports people and weapons. Also available in Jurassic Park: Operation Genesis.
• The Stegosaurus features in the BBC documentaries Walking with Dinosaurs (Time of the Titans series) and The Ballad of Big Al.
• Several stegosaurus are featured in the Jurassic segment of the Discovery movie "When Dinosaurs Roamed America". One of them digs a hole during a drought, trying to get to the aquifer, a couple of others are attacked by a ceratosaurus. Having fought off a predator with the help of a spiked tail, the male shows his brightly colored dorsal plates to the female, but she is not ready for mating. A few days later, he repeats the mating ritual, this time successfully.
• Also, the most modern and colorful image of the stegosaurus turned out in the "Fight Club of the Jurassic Period" ("Lost Worlds").
• Stegosaurus can be farmed in Zoo Tycoon 2 Extinct Animals.
• The Stegosaurus appears in Arthur Conan Doyle's The Lost World.
• He appears in Jurassic World: The Game, where he is somewhat underestimated, as he loses to the Spinosaurus, although in reality he would be stronger than him. However, it is equal in strength to the Allosaurus, which corresponds to reality.

Video

Sources

http://dinosaurs.afly.ru/stegosauria/48-stegosaurus

Detachment - Ornithischians

Family - Stegosaurs

Genus/Species - Stegosaurus stenops. Stegosaurus

Basic data:

DIMENSIONS

Length: up to 9 m.

Weight: 6-8 tons.

Head length: about 45 cm.

Brain size: 3 cm

Back plates: up to 60 cm high.

Tail spikes: length 1 m.

BREEDING

Mating period: time unknown; perhaps there were fights between males for the right to fertilize the female.

Laying time: probably several times a year.

LIFESTYLE

Habitat: in the tropics.

Food: vegetation.

Habits: stegosaurus (see picture) probably led a herd lifestyle.

RELATED SPECIES

A 5 meter long Kentrosaurus that lived in Africa.

The dinosaur Stegosaurus lived about 170 million years ago. Despite the intimidating appearance, he was a peaceful herbivore. It is likely that he lived in herds. They gave him security more by their numbers than by the militancy of the members of the herd.

FOOD

Stegosaurus was a herbivore and fed on many kinds of plants. In that historical period, a tropical climate prevailed on Earth in America, the earth was covered with lush vegetation.

Studies of stegosaurus fossil skeletons have shown that stegosaurus had fairly strong dorsal muscles associated with outgrowths on the hips at the base of the tail. These muscles apparently allowed the stegosaurus to stand up on its hind legs, thanks to which it reached plants that grew high. It is interesting to know that his body was not specially adapted to plant foods - his teeth were small and weak. It is believed that he, like other dinosaurs and modern crocodiles, swallowed stones to grind plant fibers.

BREEDING

One of the reasons that makes studying dinosaurs such a fascinating activity is that very little is known about them. Therefore, you can always make some kind of discovery, and the finds can be hidden in the ground right under our feet.

Dinosaurs, including Stegosaurus, are known to have laid several relatively small eggs in shallow holes dug in the ground. They covered the eggs with sand so that the sun's rays warmed them. Newborn cubs grew very quickly, thereby avoiding the fate of becoming easy prey for predators.

During the defense against attackers, the cubs were placed in the center of the herd. Since the Stegosaurus was a herd animal, the males competed for the right to possess the female and be the leader of the herd. In such situations, herbivores only make threatening sounds and demonstrate their strength to other males, but do not enter into an open fight.

ENEMIES

The peace-loving stegosaurus often fell prey to predatory dinosaurs, such as the dangerous one.

The Stegosaurus was most likely rather slow and defenseless, especially when attacked from the side and in the leg area. He was slow and therefore could not run away from predators. He defended himself by unexpectedly hitting the attacker with his tail, which was covered with spikes. Each of the spikes on the tail was about 1 m long. Stegosaurus had two pairs of them.

Some species related to Stegosaurus had four pairs of spines. The spikes were quite keratinized and could seriously injure the enemy if he fell into their reach.

SPECIAL SIGNS. DESCRIPTION

Stegosaurus is one of the dinosaurs that has a double row of bony plates along its back.

There are many theories that try to explain the purpose of the plates, the highest of which is 60 cm high. Some argue that the plates were needed for self-defense. According to other theories, they served to regulate the temperature.

If the plates were covered with skin with many blood vessels, then, being turned towards the sun, they could serve the animal for heating the body, and when placed in the shade, they cooled the body.

The Stegosaurus had four spikes at the end of its tail, which it apparently used to protect itself.

Stegosaurus did not belong to the largest dinosaurs, however, its body length reached 9 meters. The forelimbs were half as long as the hind ones, so the stegosaurus moved by leaning forward strongly.

The head of the Stegosaurus was very small, about 45 centimeters long, and almost touched the ground. His brain was also small - only about 3 cm.

WHERE THE DINOSAUR STEGOSAUR LIVED

Stegosaurus lived over 170 million years ago on the ancient continent that would later form North America.

At that time, a warm, almost tropical climate prevailed there - ideal for such herbivorous dinosaurs as the Stegosaurus. The vegetation that grew on the continent, at first glance, resembled a modern rainforest, but today's plant species did not exist at that time. So, there were no flower plants. Everywhere, next to ferns and coniferous trees, ancient palm trees grew, which, in their appearance, resembled modern ones.

INTERESTING INFORMATION. DO YOU KNOW WHAT...

• Fossilized remains of a relative of the Stegosaurus have been found in Western Europe.
• Obviously, stegosaurs lived for a short time in the Jurassic period. The remains of these dinosaurs are found only in the upper layers of rocks.
• Some modern reptiles look like smaller versions of extinct dinosaurs.
• The lizard, which lives in Africa, has spikes on its head and body, similar to those that were in a stegosaurus. However, this lizard is 60 times smaller than a Stegosaurus, and its length reaches only 60 cm.

CHARACTERISTIC FEATURES OF THE STEGOSAUR

Back plates: went from head to tail. There are many theories that explain their purpose, including one that suggests that they served to regulate body temperature.

Head: small compared to the large body. The brain is the size of a walnut.

Forelimbs: much shorter than the rear, designed for walking.

Hind limbs: strong, capable of bearing the weight of the entire body of the animal.

- Habitat of Stegosaurus

WHERE AND WHEN THE STEGOSAUR LIVED

The dinosaur Stegosaurus lived during the late Jurassic period 170 million years ago in North America. Its fossilized footprints have been found in Colorado, Oklahoma, Utah, and Wyoming. It is not uncommon for Stegosaurus footprints to be found in large numbers and extend for many kilometers. Other members of the Stegosaurus family lived in places like Western Europe, East Asia, and East Africa.

What in Latin sounds like "covered lizards" or "roof lizards" are a genus of herbivorous ornithischian herbivorous dinosaurs that existed on Earth during the breakup of the supercontinent Pangea in the Middle Jurassic (Fig. 1). The main number of diverse individuals assigned to this infraorder, scientists find in the deposits of the Kimmeridgian stage, and dates back to 155-145 million years ago. n.

Opening of the infraorder "Stegosaurs"

The first more or less preserved Stegosaurus skeleton, namely - stegosaurus armatus, was discovered by Yale University professor Charles Marsh during excavations north of the town of Morrison in Colorado back in 1877. Name "Stegosaurus" was given to the reptile on the grounds that its skeleton was covered from above with horny plates, which Marsh at first perceived as a kind of peculiar “roof”, vaguely resembling a tortoise shell, but at the same time located only on the back of a dinosaur, while the tortoise shell covers all of them whole body.

Subsequently, many varieties of stegosaurs were found on other continents of the planet, but scientists suggest that the ancestors of this infraorder are considered to be the ancient ovoid archosaurs that evolved in the African part of the supercontinent. Subsequently, from there they spread to South and North America, and already in the Jurassic period they settled along Pangea, which was not yet split in the northern part, into the Eurasian territory.

Rice. 1 - Stegosaurus

In our country, from time to time, paleontologists also managed to find fragmentary parts of the skeletons of these ancient creatures. But the most complete and well-preserved remains of a stegosaurus found on the territory of Russia are the skeleton of an individual found in the Krasnoyarsk Territory among the Carboniferous deposits of the Jurassic period, dated 170-165 million years ago. n.

The vicissitudes of the description of the stegosaurus

Several incidents are associated with the description of this genus of dinosaurs.

For the first time, the Stegosaurus of the Middle Jurassic period was described by the same professor of paleontology, Charles Marsh, literally in the same year in which this find happened.

At first, the stegosaurus was described by him as an ancient tortoise, since the scientist mistook the thyroid dorsal segments for a broken shell. In that district, excavations now did not stop, and archaeologists removed from the earth more and more remains of ancient animals, as a rule, belonging to the same variety and differing only in minor deviations in the structure of certain bones. Marsh worked tirelessly, and between 1879 and 1887 he was able to describe with varying success as many as six varieties of stegosaurs, sometimes based on only a few bones of one or another individual. Finally, in 1891, it was first published illustrated reconstruction of a stegosaurus, which Marsh has been working on for the past few years.

But in 1902, another no less prominent American paleontologist, Frederick Lucas, refuted Marsh's theory that the bone plates were a kind of underdeveloped shell for the dinosaur, which was a kind of “gable roof”. He put forward his theory that the shields, located along the spine, were pointed upwards, went in two rows along it from the head to the very tail, ending in massive spikes. Lucas also suggested that they served the animal as protection against flying lizards and dinosaurs, which were larger than the stegosaurus in height, in other words, they protected the animal's back from an attack from above. Less than a year later, Lucas changed his mind about the placement of the plates. If earlier he assumed that the plates went in two rows and in pairs to each other, now he claimed that they were arranged in a checkerboard pattern.

In 1910, another Yale University professor, Richard Lall, entered into a controversy with him, arguing that the staggered order of the plates was caused by the displacement of the skeleton in the ground, that is, the unevenness of its occurrence in the rocks, as a result of which the shields paired with each other shifted, thereby forming " Lukasovsky" chess order. Participating in the first reconstruction of the Stegosaurus skeleton at the Peabody Museum of Natural History, he insisted that the plates of the dinosaur be arranged exactly in pairs, in accordance with Lucas's earlier theory.

Charles Gilmour continued the argument. In 1914, he issued a statement that, having analyzed a number of stegosaur skeletons and their occurrence in the soil, he did not find evidence that the staggered arrangement of their plates was caused by rock shifting or any other natural causes and external factors, and that it was in reality is natural.

Rice. 2 - Stegosaurus Skeleton

In the end, Gilmour and Lucas prevailed in this almost half-century dispute, and subsequently, in 1924, stegosaurus reconstruction in the Peabody Museum has been modified in accordance with their theory, which is considered justified and generally accepted to this day.

Commonly accepted description of Stegosaurus

Infraorder Stegosaurus, in fact, in addition to the well-known representatives of the same name, it has two more varieties, namely, kentrosaurs and hesperosaurs. But, despite the fact that they differ slightly in their internal structure, skeletal structure and longitudinal dorsal growths, in general, in appearance, these individuals almost do not differ from each other.

For the most part, these herbivorous ornithischian representatives of the thyrophora reached 9 meters in length, 4 meters in height and weighed an average of 2 tons. Their jaws in front were equipped with a powerful beak, behind which there was a row of sharp small teeth. With their beaks, the animals broke off branches, with their teeth they ground them, and the greens on them, into porridge. Stegosaurus moved on four limbs, but occasionally they could also rise on their hind legs, for example, to pluck foliage from high-lying branches. At first, Marsh thought that the stegosaurus was a bipedal lizard, but later abandoned this assumption, although the dinosaur's forelimbs were indeed half as short and less developed than the hind ones. It is possible that an offshoot of the ancient Early Triassic thyreophores, which became the progenitors of the infraorder Stegosaurs, initially preferred to move on their hind limbs, due to which the forelimbs began to decrease in size. But later, for some reason, the animals again preferred to stand on four legs.

Sacral thickening of stegosaurus

What is characteristic, with its impressive dimensions brain of stegosaurus weighed no more than 70 grams, which gave the right to Charles Marsh, the first to discover the skeleton of a stegosaurus, to conclude that these reptiles were exceptionally short in their mental development.

But upon further study of the skeleton in its sacral part, Marsh discovered a thickening of the spinal canal, which gave reason to say that this receptacle contained 20 times more brain tissue than the brain itself. From that moment on, theories were put forward, one more contradictory than the other. Most scientists came down to the assumption that it was this section of the spinal cord that was responsible for all the reflexes of the body, thereby greatly unloading the brain and leaving a wide space for thought processes.

Another theory was that since the Stegosaurus was basically a massive and well-protected herbivore, there was absolutely nothing for it to think about, except that it needed to constantly chew, swallow, or sometimes stand on its hind limbs in order to get more attractive thread. For this, it is quite possible to get by with a 5-sanimeir brain. But for defense in a battle with predators, you would have to think, but this function was elevated to the category of reflex, for which the more extensive sacral brain.

Rice. 3 - Sacral thickening of a stegosaurus

But, as it turned out later, stegosaurs were not the only representatives of the animal world, the spine of which contained a specific thickening in this place. This anomaly was also found in the spines of many sauropods, and, most importantly, in the spines of modern birds, from which the scientists were able to conclude that in this section there was a kind of glycogen body, the purpose of which is still unknown, but it is precisely established that it is by no means way cannot help vertebrates to think. It simply supplies the brains of animals with glycogen, but for what it is needed, there is no answer yet.

Appointment of plates and tail spikes

So it has not yet been clarified exactly why these ancient ornithischians needed plates. The theory put forward in early times that plates of stegosaurus served as protection when attacked from above, it did not stand up to criticism, since the horn plates were very fragile, and in no way resembled defensive shields. It was not difficult for predators such as allosaurs to gnaw them, not to mention tyrannosaurs and other giant predatory theropods. In addition, in a collision with them, no special damage could be inflicted, since they were sometimes so blunt that they not only could not cut through the rough cellular skin of predators, but, on the contrary, they themselves could be injured from a strong blow to them.

Some have suggested that predators, in view of their narrow mind, like real dogs, bite their teeth into everything that sticks out and into everything that is convenient to cling to. These very features were possessed by the dorsal plates of stegosaurus. While allosaurs and other predators ruffled their plates, the animal itself, spreading its limbs widely, led the defense with its spike-like tail, and after the defeat of one or several aggressive individuals, the predators allegedly simply retreated without causing any tangible damage to the stegosaurus.

Another assumption of scientists is based on the fact that plates were needed by stegosaurus for thermoregulation. It is possible that these porous horn formations could be completely saturated with a frequent network of small blood vessels, and thus perfectly suited to cool the body in extreme heat according to the principle of elephant or hare ears.

The fact that stegosaurs could quite effectively defend themselves and deliver lethal blows with their powerful spiked tail is evidenced by excavations. A considerable number of the same allosaurs with holes in the body have already been found, one to one suitable for the size and other parameters of the tail spikes of stegosaurus.

Habitats and food of stegosaurus

Scientists suggest that all ornithischians began to spread across the ancient continent of Pangea, which in the early Triassic was still a single supercontinent, from its African territory. Since the path to the European part, which was more distant at that time, was closed by the ancient ocean, ancestors of stegosaurs, early thyreophores were evenly distributed throughout Africa and South America and Antarctica, between which at that time there was no water separation. Further, the animals moved north to the territory of North America and Europe, and after that they settled throughout the entire Asian territory of Pangea. At the end of the Triassic, the beginning of the Jurassic, the separation of the continents from the main part of the supercontinent began, and in the Cretaceous period this already acquired a pronounced global scale, due to which individual branches of animals subsequently evolved in their own way. In various continental parts, between which migratory routes have been disrupted, more and more new varieties of stegosaurs are still found, although they often differ from the main branch only in their size and neck length.

Rice. 4 - Stegosaurus

So, in areas where low types of vegetation flourished, reptiles did not need long necks. It was not difficult to pick juicy foliage from the trees here. But in places where taller trees grew, evolution had to work hard to produce reptiles with a longer neck, equipped with additional cervical vertebrae. One of these varieties was Miragayalongicollum, which lived in the Upper Jurassic on the territory of present-day Europe and, in particular, in Portugal, where the remains of these individuals were found. If the main varieties of stegosaurus number of cervical vertebrae varied from 12 to 13, then this species had as many as 17. This gives the right to say that Miragaya, having all the features of a stegosaurus, namely, horny dorsal shields and tail spikes, looked more like a diplodocus or on other sauropods.

The genus Stegosaurid differed mainly in that instead of shield plates, its back along the vertebra had two rows of long and massive spikes. In the case of kentrosaurs, those spikes that are located only on the tail in ordinary stegosaurs go all over the body through the entire neck up to the back of the head, with the only difference being that they become slightly wider closer to the neck, which indicates that that earlier they most likely had the form of plates.

Rice. 5 - Kentrosaurus

(Fig. 5) reached a length of up to 5.5 m and at the same time had a relatively low height - only 1.5-2 m. In order to eat, according to scientists, he quite often had to stand on his hind legs, since the animal had a very short neck and short forelimbs. By the way, on the shoulder blades of the forelimbs, Kentrosaurs also had a massive spike-like formation.

Hesperosaurs

Another genus stegosaurus belonging to the stegosaurid family. The main distinguishing feature of this variety is that in this lizard, the thyroid growths along the vertebrae went only in one row, and although they were extremely massive, they were located much less frequently from each other than in the "chess" varieties.

Hesperosaurs reached an average length of 6.5 m with a total weight of more than 3.5 tons. These varieties lived in the North American part of Pangea, in what is now the state of Wyoming.

With the general diversity and abundance of stegosaurs in the Jurassic, it is very strange that these ornithischians are almost never found in the Cretaceous deposits. This gives reason to say that for some reason the overwhelming number of species of these animals died out at the border of the Jurassic and Cretaceous.

A unique genus, recognizable by scientists even at a distance. Why? is the accepted Latin name. But it comes from two Greek words: roof (stegos) - lizard (sauros). The animal received it due to the main distinguishing feature - the presence of a number of large leaf-shaped plates on the back. Against the background of a large body, a small head is especially contrasting.

Business card

Time and place of existence

They lived at the end of the Jurassic period about 155.7 - 145.5 million years ago. All species are found in the closer to the west of the United States (Colorado and Wyoming).

The drawing by Zdeněk Burian is one of the reconstructions in the habitat. There are clear footprints in the wet soil, which could have been used by predators such as Allosaurus or Ceratosaurus to detect stegosaurids.

Types and history of discovery

Three types of stegosaurs are now considered generally recognized. The rest either did not find sufficient evidence, or were included in the main ones. Stegosaurus armatus was described by the famous professor G. Marsh in 1877. It was also one of the first officially found remains of dinosaurs in general. They were excavated north of the small American town of Morrison. Stegosaurus stenops and Stegosaurus longispinus were smaller.

body structure

The body length of this creature reached 9 meters (comparative dimensions are shown in the figure). The height is up to 4 m. The representative weighed 4.5 tons.

On the back was a whole series of plates. The discoverer of the skeleton, G. Marsh, erroneously assumed that they were connected to each other like tiles covering the back. However, it is now known that they were located perpendicular to the body of the animal. Namely, two parallel rows at some distance from each other in such a way that the sheet of one row was opposite the gap of the other. There was also a gap between the "leaves" of the stegosaurus. Really handsome - do not say anything.

The purpose of the plates is still not exactly known. The discoverers at first assumed that the plates protected it from the attacks of carnivorous dinosaurs. However, a detailed study of these by the scientific community in 1970 showed that they were fragile and did not pose any physical danger. Yes, and the attackers could easily hit the side of the body. Thus, now there are three options: defensive and two peaceful.

The first suggests that the plates were painted in bright colors (and maybe the whole Stegosaurus). Appearing in such a prickly painted form near a predator, he could scare away or at least puzzle the offender. If the second happened, then the tail came to the rescue, with which it was possible to deliver an aimed blow.

The second option - each plate was pierced by large blood vessels. This design of the circulatory system made it possible to cool the body in case of extreme heat and, conversely, quickly accumulate heat on cold mornings. After all, the Stegosaurus was a cold-blooded reptile.

The third case - the shape and color of the plates may have played a significant role in building relationships in a group of animals. Moreover, they could be used by males in mating games. There is also Robert Becker's suggestion that stegosaurus could even move bone decorations up and down. Such nine-meter peacocks moving the plates and filling them with blood more than compensate for grace with assertiveness. In fact, all three assumptions could be true - it was a universal tool.

Separately, it is worth mentioning the tail. At the end of it, sharp spikes were attached, which, unlike plates, could cause significant damage to a careless predator. The blow of a powerful tail was able to stun and leave even a mortal wound.

Stegosaurus skeleton

The photo shows museum exhibits of the species Stegosaurus stenops.

Skull on close examination of the same species.

Nutrition and lifestyle

Stegosaurs cut low vegetation with adapted teeth. However, there are suggestions that grass and shrubs were not the only food. The dinosaur's hind limbs were much larger than its front limbs, so there is a possibility that it could stand on them (for a short time) to pluck the lower branches of trees.

It is a symbol of the American state of Colorado, where it was first excavated in the 19th century by the pioneers of paleontology.

Video

An excerpt from the documentary "Mammals vs Dinosaurs". On the plain, where a group of stegosaurs peacefully grazes, a thunderstorm of the late Jurassic - Allosaurus is selected. The first mammals tremblingly watch the giants from the high thickets.