Stegosaurus is a predator or herbivore. Ankylosaurs. Spiny Dinosaurs: Stegosaurus

Stegosaurus

Stegosaurs(Latin Stegosaurus - “roof lizard”) - a genus of Late Jurassic herbivorous dinosaurs that existed 155-145 million years ago (Kimmeridgian Stage). It contains three species. Thanks to the spines on the tail and the bony plates on the back, they are one of the most recognizable dinosaurs.

The first fossil remains of a stegosaurus (Stegosaurus armatus) were discovered by G. Marsh in 1877 north of the town of Morrison, Colorado. The name was compiled by Marsh from the Greek. στ]γος (roof) and σαρος (lizard), since the paleontologist believed that the plates lay on the back of the dinosaur and formed something like a gable roof. At first, many species of stegosaurs were described, which were later combined into three.

Marsh believed that the stegosaurus walked only on two legs, since the forelimbs were significantly shorter than the hind limbs. However, already in 1891, having assessed the physique of the dinosaur, he changed his mind.

Stegosaurus had a brain the size of Walnut; however, thanks to the bone plates, he was able to perfectly control his body temperature and defend himself. The stegosaurus was forced to spend most of its time looking out for any of its many ferocious predators on the horizon. But at the slightest opportunity, this plate-protected dinosaur used its toothless beak and ate the nearby vegetation.

The skeletal remains of a stegosaurus are easily distinguishable thanks to the impressive row of plates running along the entire back of this animal. These plates served as good armor, protecting at least to a certain extent from predators such as the terrible Allosaurus. The tail was equipped with spikes and thus could be used to deliver effective side blows.

But these plates were useful even when there were no predators nearby. If on an early Jurassic morning, when the temperature was probably quite low, the stegosaurus turned its side to the sun so that the sun's rays fell on the wide sides of the plates, its whole body gradually warmed up.

At midday, however, it could become too hot. This animal could then turn itself so that the plates would not absorb as much heat.

In many respects, such a heating system is similar to absorbent solar heat special panels that some modern houses are equipped with. The scientists also found signs on the plates that there may have been blood vessels running through them. At first, some scientists even argued that these plates could change their position, so that the stegosaurus could lower them horizontally. But today this theory does not find much support.

Recognized species:

Stegosaurus armatus - first open view, known from two incomplete skeletons, two skulls, and individual bones from at least 30 individuals. It had 4 spikes on its tail and relatively small plates, reaching a length of 9 meters.

Stegosaurus stenops - Described by Marsh in 1887 from fossils from Colorado. A complete skeleton of a representative of the species and about 50 fragmentary ones were found. It was smaller than S. armatus, reaching only 7 meters, but had larger plates.

Stegosaurus longispinus - described by Charles Gilmore from one incomplete skeleton from Wyoming. It also reached 7 meters, but had the longest spines. Some researchers refer to the genus Kentrosaurus.

The only one in Russian Federation skeleton of a stegosaurus found in Jurassic deposits (170-165 million years ago) of a coal mine in the Sharypovsky region Krasnoyarsk Territory, exhibited in the Krasnoyarsk Museum of Local Lore.

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

Time and place of existence

Lived at the end Jurassic period about 155.7 - 145.5 million years ago. All species are found in the western United States (Colorado and Wyoming).

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

The drawing by Zdenek Burian shows one of the reconstructions in the habitat. There are clear tracks in the wet soil that could have been used by predators such as Allosaurus or Ceratosaurus to detect stegosaurids.

INTERESTING INFORMATION. DID YOU KNOW THAT...

• IN Western Europe The fossilized remains of a relative of the stegosaurus were found.
• Obviously, stegosaurs lived for a short time in the Jurassic period. The remains of these dinosaurs are found only in upper layers rocks.
• Some modern reptiles his appearance resemble smaller copies of extinct dinosaurs.
• The lizard, which lives in Africa, has spines on its head and body, similar to those on the stegosaurus. However, this lizard is 60 times smaller than a stegosaurus, and its length reaches only 60 cm.

Types and history of discovery

There are currently three generally accepted species of stegosaurs. 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 back in 1877. These were also one of the first officially found remains of dinosaurs in general. They were excavated north of the small American city Morrison. Stegosaurus stenops And Stegosaurus longispinus were smaller in size.

Body structure

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

There was a whole series of plates on the back. The discoverer of the skeleton, G. Marsh, mistakenly 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. Precisely 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 - nothing to say.

The purpose of the plates is still unknown exactly. Discoverers first theorized that the plates protected it from attacks predatory dinosaurs. However, a detailed study of them scientific community in 1970 showed that they were fragile and did not pose any physical danger. And the attackers could easily hit the side of the body. Thus, now there are three options left: defensive and two peaceful.

The first suggests that the plates were painted in bright colors (and perhaps the entire stegosaurus). Presenting itself in such a spiky, painted form near a predator, it could scare away or at least puzzle the offender. If the latter happened, then the tail came to the rescue, with which it was possible to deliver a targeted blow.

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

The third case is that 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 an assumption by Robert Becker that stegosaurs could even move bone decorations up and down. These nine-meter-tall peacocks, moving their 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 were attached sharp spikes, which, unlike plates, could cause significant damage to an unwary predator. The blow of the powerful tail could stun and even leave a mortal wound.

Stegosaurus skeleton

The photo shows museum exhibits of the species Stegosaurus stenops.

A close-up view of the skull of the same species.

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

Purpose of plates and tail spikes

It is still not clear exactly why these ancient ornithischians needed plates. The theory put forward in early times, that Stegosaurus plates served as protection when attacked from above, did not stand up to criticism, since the horny plates were very fragile and did not in any way resemble defensive shields. It was not difficult for predators such as allosaurs to chew them, not to mention tyrannosaurs and other giant predatory theropods. In addition, in a collision with them, no special damage could be caused, since they were sometimes so blunt that they not only could not pierce the cellular, rough skin of predators, but, on the contrary, from strong blow they themselves could have been injured.

Some have suggested that predators, due to their narrow-mindedness, like real dogs, bite their teeth into everything that sticks out and into everything that is convenient to grab onto. The dorsal plates of stegosaurs had these same features. While allosaurus and other predators ruffled their plates, the animal itself, with its limbs spread wide, defended itself with its spike-shaped tail, and after defeating one or several aggressive individuals, the predators allegedly simply retreated without causing any significant damage to the stegosaurus.

Another assumption of scientists is based on the fact that stegosaurs needed plates for thermoregulation. It is possible that these porous horny formations could be completely saturated with a dense network of small blood vessels, and thus were excellent for cooling the body in extreme heat based on the principle of elephant or hare ears.

Excavations indicate that stegosaurs could defend themselves quite effectively and deliver lethal blows with their powerful spiked tail. A considerable number of the same allosaurs with holes in the body have already been found, one to one matching the size and other parameters of the tail spines of stegosaurs.

Nutrition and lifestyle

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

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

In culture

• Stegosaurus appeared in the film Jurassic Park 2: lost World", then there was a small scene with a stegosaurus on background in Jurassic Park 3.
• IN computer game"ParaWorld" stegosaurus either wanders through lava-scorched glades and savannas, or transports people and weapons. Also found in the game Jurassic Park: Operation Genesis.
• Stegosaurus appears in the BBC documentaries Walking with Dinosaurs (Time of the Titans) and The Ballad of Big Al.
• Several stegosaurs are depicted in the Jurassic segment of Discovery's 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 the predator with the help of his spiked tail, the male shows the female his brightly colored dorsal plates, but she is not ready for mating. A few days later he repeats marriage ritual, this time successfully.
• Also, the most modern and colorful depiction of a stegosaurus was obtained in “Jurassic Fight Club” (“Lost Worlds”).
• Stegosaurus can be raised in Zoo Tycoon 2 Extinct Animals.
• Stegosaurus appears in Arthur Conan Doyle's The Lost World.
• Appears in the game "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

Spiny Dinosaurs: Stegosaurus

The group of spiny dinosaurs includes one of the most mysterious and amazing appearance The dinosaur is a stegosaurus. What makes it unusual?

In North America, several unusual bone plates were found during excavations among dinosaur bones. The researchers suggested that the body of the discovered fossil animal was covered, by analogy with scaly animals, with a tight-fitting protective shell of horny scales. Therefore, it was precisely because of the presence of plates, presumably arranged like roofing tiles, that this lizard was called “stegosaurus”, which means “roof lizard”, or “lizard covered with scaly plates”. In fact, as it turned out later, on the back of the stegosaurus, from the neck to the tip of the tail, there were two rows of these unusual bone spikes or plates, loosely attached to the skin. It is still difficult to say how these plates were arranged, interspersed or in pairs one after the other.

The largest stegosaurus was found in North America: its length was about eight meters and it weighed over two tons. There were spiky spines only at the end of the tail, and plates protruded throughout the body, the largest of which was 76 centimeters high. Centurosaurus, a spiny-tailed dinosaur that lived in East Africa, the plates on the body gradually turned into prickly spines towards the tail, and Dacentrus, the fossilized remains of which are widely represented in Europe, had only spines on the body.

Scientists still have not come to a common opinion: what were the plates used for? The answer must be found in their lifestyle. Stegosaurs and other spiny dinosaurs were four-legged herbivores. They needed protection from predators and certain means to repel enemies. However, the bone plates themselves, which were relatively light and porous, were unsuitable for active protection. It is quite possible that the animals could deliberately direct some of their sharp spines at an enemy or predator. The stegosaurus's spiny tail, when it swung it, was dangerous for any opponent.

It is possible that the bone (horny) plates were covered thin skin and are penetrated by numerous blood vessels, and served to regulate body temperature.

The head, in size, was very small, especially when compared with the size of the body.

The head of spiny dinosaurs had a kind of beak equipped with small teeth suitable for eating soft plant food in the form of foliage and young shoots. To reach high leaves and branches, animals had to stand on their hind limbs.

Spiny and armored dinosaurs had the smallest brains compared to body size. Thus, a stegosaurus the size of an elephant had a brain only the size of a walnut! And apparently, such a brain was quite enough for the dinosaur, serenely grazing under the protection of its formidable spines, because spiny dinosaurs existed for many millions of years. More than a century ago, the American paleontologist Othniel Marsh, who first examined the complete skeleton of a giant dinosaur, stated with amazement: “The very small size of the head and brain suggests that the reptile was a stupid and slow animal...”. This opinion is so ingrained that even in everyday life the word “dinosaur” has become synonymous with antiquity and stupidity.

However, as it turned out, in the femoral region of the spine of dinosaurs there was another, relatively large cavity for the nerve center. Apparently, as some researchers claim, this thickening of the spinal cord constituted a kind of “second brain.”

More precisely, it was the control center for the nerve pathways of the back of the body and tail. And now, in most vertebrates with long tails the spinal cord has a noticeable thickening in this place. And in stegosaurs, the tail was not just huge, longer than the entire body, but also performed a vital function - it served as a weapon of defense. In order to accurately control all the muscles of the tail during a targeted strike, a sufficiently developed nervous system at the beginning of the tail.

However, the real brain is only the one contained in the skull.

Long-necked stegosaurus found in Portugal

In Europe, Portugal, an employee of the New University of Lisbon, Octavio Matheus, managed to excavate the remains of a dinosaur previously unknown to science in the village of Miragaia near the city of Lourinho. Paleontologists extracted the skull, forelimb bones and parts of the spine. They belonged to a member of the stegosaur genus, which Matheus christened Miragaia longicollum, meaning “long-necked one from Miragaia.”

The long-necked stegosaur Miragaia longicollum, which existed 150 million years ago, had a neck twice as long as other members of the genus. Stegosaurus had spines on its tail and 17 bony plates along its spine. The brain weighed about 80 g, and the stegosaurus itself pulled 4.5 tons.

Portuguese researchers were amazed by the number of its cervical vertebrae. Stegosaurs usually have 12-13 of them. Miragai saurus has 17 of them, making it similar to Diplodocus and other sauropods.

“Traditionally, stegosaurs were depicted as animals that fed on low-growing vegetation due to their short forelimbs and necks, and small heads. We have created a description of a new stegosaur that lived in Portugal during the Upper Jurassic, which refutes this traditional version. Miragaia longicollum had at least 17 cervical vertebrae, more than sauropods known for their long necks. Our study demonstrates the ecological diversity of stegosaurs,” says the scientist.

Matheus calculated that during the life of the Miragai saur, its neck reached 1.5-1.8 m and amounted to about 30% of its body length, which is twice as long as the neck of a regular stegosaurus. Short-necked stegosaurs, such as Huayangosaurus, which lived 170 million years ago, had only nine cervical vertebrae. The long neck could have appeared as a device for attracting mates or as a result of a transition to a different type of food, as happened in giraffes.

Which translates from Latin as "covered lizards" or "roof lizards" are a genus of ornithischian herbivorous dinosaurs that existed on Earth during the breakup of the Pangea supercontinent in the Middle Jurassic (Fig. 1). Scientists find the main number of various individuals assigned to this infraorder in the deposits of the Kimmeridgian Stage, and date back to 155-145 million years ago. n.

Discovery of the infraorder "Stegosaurs"

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. Title "Stegosaurus" was given to the reptile on the basis that its skeleton was covered on top with horny plates, which Marsh initially perceived as some kind of “roof”, vaguely reminiscent of the shell of a turtle, but located only on the back of the dinosaur, while the shell of turtles covers all of them whole body.

Subsequently, many species of stegosaurs were found on other continents of the planet, but scientists suggest that the ancestors of this infraorder are considered to be ancient ovociform 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 had not yet been split in the northern part, into Eurasian territory.

Rice. 1 - Stegosaurs

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 to this day found on the territory of Russia is the skeleton of an individual found in the Krasnoyarsk Territory among the coal deposits of the Jurassic period, dated 170-165 million years ago. n.

The vicissitudes of the description of the stegosaurus

There are several incidents associated with the description of this genus of dinosaurs.

The stegosaurus of the Middle Jurassic period was first described by the same professor of paleontology, Charles Marsh, literally in the same year in which this discovery occurred.

At first, the stegosaurus was described by him as ancient turtle, since the scientist mistook the thyroid dorsal segments for a broken shell. In that area, excavations now did not stop, and archaeologists extracted from the ground more and more remains of ancient animals, as a rule, belonging to the same species 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 as many as six species of stegosaurs with varying degrees of success, sometimes based on only a few bones of a particular individual. Finally, in 1891, it was published for the first time illustrated reconstruction of a stegosaurus, which Marsh has been working on for the past few years.

But in 1902, another equally outstanding 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 directed with their tips upward, running in two rows along it from the head to the tail, ending in massive spikes. Lucas also suggested that they served as protection for the animal from flying lizards and dinosaurs that 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 view on the arrangement of the plates. If earlier he assumed that the plates were double-rowed and in pairs, now he argued that they were arranged in a checkerboard pattern.

Another Yale University professor, Richard Lall, entered into a debate with him in 1910, arguing that the checkerboard 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 “ Lucas' chess order. Participating in the first reconstruction of the stegosaurus skeleton at the Peabody Museum of Natural History, he insisted that the dinosaur's plates be arranged in pairs, in accordance with Lucas's earlier theory.

Charles Gilmore continued the argument. In 1914, he made a statement that after analyzing a number of stegosaur skeletons and their occurrence in the soil, he found no evidence that the staggered arrangement of their plates was caused by shifting rocks or any other natural causes and external factors, and that it is in fact natural.

Rice. 2 - Stegosaurus skeleton

In the end, Gilmour and Lucas prevailed in this almost half-century dispute, and subsequently, in 1924, Stegosaurus reconstruction at the Peabody Museum was changed according to 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 centrosaurs 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 are almost no different from each other.

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

Sacral thickening of stegosaurs

What is characteristic, given its impressive dimensions Stegosaurus brain weighed no more than 70 grams, which gave the right to the first discoverer of the stegosaurus skeleton, Charles Marsh, to conclude that these reptiles were extremely slow in their mental development.

But upon further study of the skeleton in the sacral part, Marsh discovered a thickening spinal canal, which gave reason to say that this container 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 Stegosaurus was basically a massive and well-protected herbivore, it had absolutely nothing to think about, except that it had to constantly chew, swallow, or sometimes stand on its hind limbs in order to reach 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 one 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 Stegosaurus

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

Purpose of plates and tail spikes

It is still not clear exactly why these ancient ornithischians needed plates. The theory put forward in early times that Stegosaurus plates served as protection when attacked from above, it did not stand up to criticism, since the horn plates were very fragile and did not in any way resemble defensive shields. It was not difficult for predators such as allosaurs to chew them, not to mention tyrannosaurs and other giant predatory theropods. In addition, when colliding with them, no particular damage could be caused, since they were sometimes so blunt that they not only could not pierce the cellular, rough skin of predators, but, on the contrary, they themselves could be injured from a strong blow to them.

Some have suggested that predators, due to their narrow-mindedness, like real dogs, bite their teeth into everything that sticks out and into everything that is convenient to grab onto. The dorsal plates of stegosaurs had these same features. While allosaurus and other predators ruffled their plates, the animal itself, with its limbs spread wide, defended itself with its spike-shaped tail, and after defeating one or several aggressive individuals, the predators allegedly simply retreated without causing any significant damage to the stegosaurus.

Another assumption of scientists is based on the fact that stegosaurs needed plates for thermoregulation. It is possible that these porous horny formations could be completely saturated with a dense network of small blood vessels, and thus were excellent for cooling the body in extreme heat, similar to the principle of elephant or hare ears.

Excavations indicate that stegosaurs could defend themselves quite effectively and deliver lethal blows with their powerful spiked tail. A considerable number of the same allosaurs with holes in the body have already been found, one to one matching the size and other parameters of the tail spines of stegosaurs.

Habitats and food of stegosaurs

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. So, like the path to a more distant one at that time European part was closed by the ancient ocean, ancestors of stegosaurs, early thyreophores were evenly distributed throughout Africa and South America and Antarctica, between which there was no water division at that time. Then the animals moved north into the territory North America and Europe, and then settled throughout the Asian territory of Pangea. At the end of the Triassic and the beginning of the Jurassic, the separation of continents from the main part of the supercontinent began, and in Cretaceous period this has already acquired a pronounced global scale, which is why individual branches of animals subsequently evolved in their own way. In various continental parts, between which migration routes were disrupted, new varieties of stegosaurs are still being 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. Here, picking succulent foliage from the trees was not particularly difficult. But in places where more tall trees, evolution had to work hard to produce reptiles with more long neck, equipped with additional cervical vertebrae. One of these species was Miragaialongicollum, which lived in the Upper Jurassic in what is now Europe and, in particular, in Portugal, where the remains of these individuals were found. If the main species of stegosaurs 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 spines, in appearance was more similar in body structure to Diplodocus or on other sauropods.

The genus stegosaurus differed mainly in that instead of shield plates, its back along the vertebrae had two rows of long and massive spikes. In the case of centrosaurs, those spines, which in ordinary stegosaurs are located only on the tail, go along its entire body through the entire neck up to the occipital part of the head, with the only difference that closer to the neck they become slightly wider, 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 feed, according to scientists, it quite often had to stand on its hind legs, since the animal had a very short neck and short forelimbs. By the way, centrosaurs also had a massive spike-like formation on the shoulder blades of the forelimbs.

Hesperosaurs

Another genus stegosaurs, belonging to the family Stegosauridae. Main distinctive 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 “chessboard” varieties.

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

Given the general diversity and number of stegosaurs in the Jurassic period, it is very strange that these ornithischians are almost never found in Cretaceous deposits. This gives reason to say that for some reason the overwhelming number of species of these animals became extinct at the boundary of the Jurassic and Cretaceous.

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

Business card

Time and place of existence

The drawing by Zdenek Burian shows one of the reconstructions in the habitat. There are clear tracks in the wet soil that could have been used by predators such as Allosaurus or Ceratosaurus to detect stegosaurids.

Types and history of discovery

Body structure

There was a whole series of plates on the back. The discoverer of the skeleton, G. Marsh, mistakenly 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. Precisely 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 - nothing to say.

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

The first suggests that the plates were painted in bright colors (and perhaps the entire stegosaurus). Presenting itself in such a spiky, painted form near a predator, it could scare away or at least puzzle the offender. If the latter happened, then the tail came to the rescue, with which it was possible to deliver a targeted blow.

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

The third case is that 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 an assumption by Robert Becker that stegosaurs could even move bone decorations up and down. These nine-meter-tall peacocks, moving their 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 were attached sharp spikes, which, unlike plates, could cause significant damage to an unwary predator. The blow of the powerful tail could stun and even leave a mortal wound.

Stegosaurus skeleton

A close-up view of the skull of the same species.

Nutrition and lifestyle

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

Video