Jurassic period the most famous of all periods of the Mesozoic era. Most likely, such fame Jurassic period acquired thanks to the film "Jurassic Park".

Jurassic tectonics:

At first Jurassic period the single supercontinent Pangea began to break up into separate continental blocks. Shallow seas formed between them. Intense tectonic movements at the end Triassic and at the beginning Jurassic periods contributed to the deepening of large bays, which gradually separated Africa and Australia from Gondwana. The gulf between Africa and America has deepened. Depressions formed in Eurasia: German, Anglo-Paris, West Siberian. The Arctic Sea flooded the northern coast of Laurasia. It was due to this that the climate of the Jurassic period became more humid. Jurassic period.

During the Jurassic period The outlines of the continents begin to form: Africa, Australia, Antarctica, North and South America.
And although they are located differently than now, they were formed precisely in

This is what the Earth looked like at the end of the Triassic - the beginning

Jurassic period

about 205 - 200 million years ago Jurassic period This is what the Earth looked like at the end of the Jurassic period around 152 million years ago. Jurassic climate and vegetation: Volcanic activity of the end of the Triassic - the beginning caused sea transgression. The continents were divided and the climate in Jurassic period Jurassic period became wetter than in the Triassic. In place of deserts Jurassic period Triassic period
, V Jurassic period lush vegetation grew. Huge areas were covered with lush vegetation. Forests mainly consisted of ferns and gymnosperms. Warm and humid climate Jurassic period ginkgos were very widespread. Groves of ginkgo trees grew throughout the belt.
The southern plant belt was dominated by cycads and tree ferns.
Ferns Jurassic period and are still preserved in some parts of the wild today. Horsetails and mosses were almost no different from modern ones. Places where ferns and cordaites grow Jurassic period now occupied by tropical forests, consisting mainly of cycads. Cycads are a class of gymnosperms that predominated in the green cover of the Earth mainly consisted of ferns and gymnosperms.. Nowadays they are found here and there in the tropics and subtropics. Dinosaurs roamed under the shade of these trees. Externally, cycads are so similar to low (up to 10-18 m) palm trees that they were even initially identified as palm trees in the plant system.
IN Jurassic period Ginkgos are also common - deciduous (which is unusual for gymnosperms) trees with an oak-like crown and small fan-shaped leaves. Only one species has survived to this day - Ginkgo biloba. The first cypress and, possibly, spruce trees appear precisely during the brisk period. Coniferous forests Jurassic period were similar to modern ones.

Land animals Jurassic period:

Jurassic period - Dawn of the Age of Dinosaurs. It was the lush development of vegetation that contributed to the emergence of many species of herbivorous dinosaurs. The increase in the number of herbivorous dinosaurs gave impetus to the increase in the number of predators. Dinosaurs settled all over the land and lived in forests, lakes, and swamps. The range of differences between them is so great that family ties between them are established with great difficulty. Jurassic period Diversity of dinosaur species in

it was great. They could be the size of a cat or chicken, or they could reach the size of huge whales. Jurassic period One of the fossil creatures , combining the characteristics of birds and reptiles, is Archeopteryx

, or first bird. His skeleton was first discovered in the so-called lithographic shales in Germany. The discovery was made two years after the publication of Charles Darwin's On the Origin of Species and became a strong argument in favor of the theory of evolution. Archeopteryx still flew quite poorly (gliding from tree to tree), and was approximately the size of a crow. Instead of a beak, it had a pair of toothy, albeit weak, jaws. It had free fingers on its wings (of modern birds, only hoatzin chicks have them).

Kings of the Jurassic Sky: Jurassic period IN Jurassic period Winged lizards - pterosaurs - reigned supreme in the air. They appeared in the Triassic, but their heyday was precisely Pterosaurs were represented by two groups pterodactyls And .

Pterodactyls were in most cases tailless, varying in size - from the size of a sparrow to a crow. They had wide wings and a narrow skull elongated forward with a small number of teeth in the front. Pterodactyls lived in large flocks on the shores of the lagoons of the Late Jurassic Sea. During the day they hunted, and at nightfall they hid in trees or rocks. The skin of pterodactyls was wrinkled and bare. They ate mainly fish or carrion, sometimes sea lilies, mollusks, and insects. In order to fly, pterodactyls were forced to jump from cliffs or trees.

IN Jurassic climate and vegetation: the first birds or something in between birds and lizards appear. Creatures that appeared in Jurassic period and having the properties of lizards and modern birds are called Archeopteryx.

The first birds were Archeopteryx, the size of a pigeon. Archeopteryx lived in forests. They ate mainly insects and seeds. Jurassic period But Jurassic period is not limited to just animals. Thanks to climate change and rapid development of flora.

, the evolution of insects accelerated dramatically, and as a result, the Jurassic landscape was eventually filled with the endless buzzing and crackling sounds of many new species of insects crawling and flying everywhere. Among them were the predecessors of modern ants, bees, earwigs, flies and wasps

Masters of the Jurassic Seas: Jurassic period As a result of the split of Pangea,

, new seas and straits were formed, in which new types of animals and algae developed. Jurassic period Compared to the Triassic, in mainly consisted of ferns and gymnosperms. The population of the seabed has changed greatly. Bivalves displace brachiopods from shallow waters. Brachiopod shells are replaced by oysters. Jurassic climate and vegetation: Bivalve mollusks fill all life niches of the seabed. Many stop collecting food from the ground and switch to pumping water using their gills. In warm and shallow seas Other important events also took place. IN folds up

new type Jurassic period reef communities, approximately the same as what exists now. It is based on six-rayed corals that appeared in the Triassic. The resulting giant coral reefs sheltered numerous ammonites and new species of belemnites (old relatives of today's octopuses and squids). They also housed many invertebrates, such as sponges and bryozoans (sea mats). Gradually, fresh sediment accumulated on the seabed. crocodiles, widely spread across the globe. There were also saltwater crocodiles with long snouts and sharp teeth for catching fish. Some of their varieties even grew flippers instead of legs to make swimming more convenient. Tail fins allowed them to develop in water higher speed

than on land.

New species of sea turtles have also appeared.

All dinosaurs of the Jurassic period Herbivorous dinosaurs: Jurassic geological period, Yura,

Jurassic system

, middle Mesozoic period. It began 206 million years ago and lasted 64 million years.

Jurassic deposits were first described in the Jura (mountains in Switzerland and France), hence the name of the period. The deposits of that time are quite diverse: limestones, clastic rocks, shales, igneous rocks, clays, sands, conglomerates, formed in a variety of conditions.

190-145 million years ago during the Jurassic period, the single supercontinent Pangea began to break up into separate continental blocks. Shallow seas formed between them.

Climate

The climate in the Jurassic period was humid and warm (and by the end of the period - arid in the equator region). During the Jurassic period, vast areas were covered with lush vegetation, primarily diverse forests. They mainly consisted of ferns and gymnosperms.

Cycads

- a class of gymnosperms that predominated in the green cover of the Earth. Nowadays they are found here and there in the tropics and subtropics. Dinosaurs roamed under the shade of these trees. Externally, cycads are so similar to low (up to 10-18 m) palm trees that even Carl Linnaeus placed them among palm trees in his plant system.

Compared to the Triassic, the population of the seabed has changed greatly. Bivalves displace brachiopods from shallow waters. Brachiopod shells are replaced by oysters. Bivalve mollusks fill all life niches of the seabed. Many stop collecting food from the ground and switch to pumping water using their gills. A new type of reef community is emerging, approximately the same as what exists now. It is based on six-rayed corals that appeared in the Triassic.

Land animals

One of the fossil creatures of the Jurassic period, combining the characteristics of birds and reptiles, is Archeopteryx, or the first bird. His skeleton was first discovered in the so-called lithographic shales in Germany. The discovery was made two years after the publication of Charles Darwin's On the Origin of Species and became a strong argument in favor of the theory of evolution. Archeopteryx still flew quite poorly (gliding from tree to tree), and was approximately the size of a crow. Instead of a beak, it had a pair of toothy, albeit weak, jaws. It had free fingers on its wings (of modern birds, only hoatzin chicks have them).

During the Jurassic period, small, furry, warm-blooded animals called mammals lived on Earth. They live next to dinosaurs and are almost invisible against their background.

Dinosaurs of the Jurassic period (“terrible lizards” from Greek) lived in ancient forests, lakes, and swamps. The range of differences between them is so great that family ties between them are established with great difficulty. They could be the size of a cat or chicken, or they could reach the size of huge whales. Some of them walked on all fours, while others ran on their hind legs. Among them were dexterous hunters and bloodthirsty predators, but there were also harmless herbivores. The most important feature common to all their species is that they were terrestrial animals.

Page 3 of 4

Jurassic period- This is the second (middle) period of the Mesozoic era. It begins 201 million years before our times, lasts 56 million years and ends 145 million years ago (according to other sources, the duration of the Jurassic period is 69 million years: 213 - 144 million years). Named after the mountains Yura, in which its sedimentary layers were first identified. Notable for the widespread proliferation of dinosaurs.

Main subsections of the Jurassic period, its geography and climate

In accordance with the classification adopted by the International Union of Geological Sciences, The Jurassic period is divided into three divisions- Lower - Leyas (stages - Hettangian, Sinemurian, Pliensbachian, Toarcian), Middle - Dogger (stages - Aalenian, Bayocian, Bathian, Callovian) and Upper Small (stages - Oxfordian, Kimmeridge, Tithonian).

Jurassic period	Departments	tiers
	Leyas (Lower)	Hettangian
		Sinemyursky
		Pliensbachian
		Toarsky
	Dogger (Medium)	Aalensky
		Bayocian
		Bathian
		Callovian
	Small (Upper)	Oxford
		Kimmeridge
		Titonian

During this period, the division of Pangea into component blocks - continents - continued. Upper Laurentia, which later became North America and Europe, finally separated from Gondwana, which again began to move south. As a result of this, the connection between global continents was disrupted, which had an important impact on the further evolution and development of flora and fauna. The differences that arose at that time are sharply expressed to this day.

The Tethys Sea, which expanded even more as a result of the divergence of the continents, now occupied most modern Europe. It originated from the Iberian Peninsula and, crossing the south and southeast of Asia diagonally, came out in Pacific Ocean. Most of what is now France, Spain and England were under its warm waters. On the left, as a result of the separation of the North American section of Gondwanaland, a depression began to emerge, which in the future became the Atlantic Ocean.

With the beginning of the Jurassic era, the average temperature on the globe gradually began to decrease, and therefore in the lower part Jurassic climate was close to temperate - subtropical. But closer to the middle, the temperature began to rise again, and by the beginning of the Cretaceous period the climate became a greenhouse.

Ocean levels rose and fell slightly throughout the Jurassic, but the average sea level height was an order of magnitude higher than in the Triassic. As a result of the divergence of continental blocks, a great many small lakes were formed, in which both plant and animal life began to develop and progress very quickly, so that the quantitative and qualitative level of flora and fauna of the Jurassic period soon caught up and surpassed the Permian level to the point of worldwide mass extinction.

Sedimentation

With a drop in temperature throughout the earth, multiple precipitation began to fall abundantly, which contributed to the advancement of vegetation, and then the animal world, into the depths of the continents, which is due to Jurassic sedimentation. But the most intense products for this period are the formation of the earth's crust under the influence of continental shifts, and as a consequence - volcanic and other seismic activity. These are various igneous, clastic rocks. There are large deposits of shale, sand, clay, conglomerates, and limestone.

The warm and stable climate of the Jurassic period greatly contributed to the rapid development, formation and evolutionary improvement of both previous and new life forms.

(Fig. 1) rose to a new level in comparison with the sluggish Triassic, which did not particularly shine with varieties.

Rice. 1 - Animals of the Jurassic period

The Jurassic seas were full of various marine invertebrates. Belemnites, ammonites, and all kinds of crinoids were especially numerous. And although there were an order of magnitude fewer ammonites in the Jurassic than in the Triassic, they for the most part had a more developed body structure than their ancestors from the previous era, with the exception of phyloceras, which did not change at all during the millions of years of transition from the Triassic to the Jurassic. It was at that time that many ammonites acquired their indescribable mother-of-pearl coating, which has survived to this day. Ammonites were found in large quantities, both in the distant oceanic depths and in the warm coastal and inland seas.

Belemnites reached unprecedented development in the Jurassic era. They gathered in flocks and roamed the depths of the sea in search of unwary prey. Some of them at that time reached three meters in length. The remains of their shells, nicknamed “devil’s fingers” by scientists, are found almost everywhere in Jurassic sediments. There were also numerous bivalve mollusks belonging to the oyster species. At that time, they began to form peculiar oyster banks. Numerous sea ​​urchins

, which abundantly populated reef areas at that time. Some of them have successfully survived to this day. But many, such as elongated hedgehogs of irregular shapes that had a jaw apparatus, became extinct. Insects also took a big step in their development. Their visual, flying and other devices were increasingly improved. More and more varieties appeared among barnacles, decapods, and leaf-footed crustaceans; most freshwater sponges and caddisflies multiplied and evolved. Ground Jurassic insects a large number of pollinating insects that feed on flower nectar.

But it was reptiles that achieved the greatest development in the Jurassic era - dinosaurs. By the middle of the Jurassic period, they completely took over all land areas, displacing or destroying their reptilian predecessors, from whom they descended, in the pursuit of food.

In the depths of the sea, already at the beginning of the Jurassic period, dolphin-like ichthyosaurs. Their long heads had strong elongated jaws, studded with rows of sharp teeth, and large, highly developed eyes were framed by bone-plate rings. By the middle of the period they had become real giants. The length of the skull of some ichthyosaurs reached 3 meters, and the body length exceeded 12 meters. The limbs of these aquatic reptiles evolved under the influence of underwater life and consisted of simple bony plates. Elbows, metatarsals, hands and fingers ceased to differ from each other; one huge flipper supported more than a hundred bone plates of various sizes. The shoulder and pelvic girdles became underdeveloped, but this was not necessary, since mobility in the aquatic environment was ensured by additionally grown powerful fins.

Another reptile that seriously and permanently settled in the depths of the sea was plesiosaur. They, like ichthyosaurs, arose in the seas during the Triassic period, but in the Jurassic period they branched into two varieties. Some had a long neck and a small head (plesiosaurs), others had an order of magnitude larger head, and a much shorter neck, which made them look more like underdeveloped crocodiles. Both of them, unlike ichthyosaurs, still needed rest on land, and therefore often crawled onto it, becoming the prey of land giants, such as, for example, a tyrannosaurus or herds of smaller predatory reptiles. Very agile in the water, on land they were the clumsy fur seals of our time. Pliosaurs were much more maneuverable in the water, but what plesiosaurs lacked in agility they made up for with their long necks, which allowed them to instantly grab prey no matter what position their bodies were in.

All kinds of fish species multiplied unusually in the Jurassic period. The water depths were literally teeming with a motley variety of coral ray-finned, cartilaginous and ganoids. Sharks and rays were also diverse, still constituting, due to their extraordinary agility, speed and agility developed over hundreds of millions of years of evolution, Jurassic underwater reptile predators. Also during this period, many new varieties of turtles and toads appeared.

But the terrestrial diversity of reptile dinosaurs was truly remarkable.

(Fig. 2) were from 10 centimeters to 30 meters in height. Many of them were simple harmless herbivores, but often there were also ferocious predators.

Rice. 2 - Jurassic Dinosaurs One of the largest herbivorous dinosaurs was brontosaurus

(now - Apatosaurus). Its body weighed 30 tons, its length from head to tail reached 20 meters. And despite the fact that his height at the shoulders reached only 4.5 meters, with the help of his neck, which reached a length of 5-6 meters, they perfectly ate up tree foliage. But the largest dinosaur of that era, as well as the absolute champion among all animals of the Earth of all times, was a 50-ton herbivore brachiosaurus

. With a body length of 26 m, he had such a long neck that when it stretched upward, his small head was 13 meters above the ground. To feed itself, this huge reptile needed to consume up to 500 kg of green mass every day. It is noteworthy that with such truly gigantic body sizes, his brain weighed no more than 450 grams. It is appropriate to say a few words about predators, of which there were also many in the Jurassic period. The most gigantic and dangerous predator of the Jurassic is considered to be 12 meters tyrannosaurus , but as scientists have proven, this predator was more opportunistic in its views on food. He rarely hunted, often preferring carrion. But they were truly dangerous allosaurus

. With a height of 4 meters and a length of 11 meters, these reptile predators hunted prey that was many times larger than them in weight and other parameters. Often they, huddled in a herd, attacked such herbivorous giants of that era as the Camarasaurus (47 tons) and the aforementioned Apatosaurus.

In view of the ever-increasing danger from predatory individuals, evolution has awarded some herbivorous individuals with formidable elements of defense. For example, such a herbivorous dinosaur as centrosaurus was endowed with elements of protection in the form of huge sharp spikes on the tail and sharp plates along the ridge. The spikes were so large that with a strong blow, the Kentrosaurus would have pierced through a predator such as a Velociraptor or even a Dilophosaurus.

For all that animal world Jurassic period was carefully balanced. The population of herbivorous lizards was regulated by predatory lizards, predators were restrained by many smaller predators and aggressive herbivores, like stegosaurs. Thus, the natural balance was maintained for many millions of years, and what contributed to the extinction of dinosaurs in Cretaceous period it is still not known.

By the mid-Jurassic period, the airspace was filled with many flying dinosaurs such as Pterosaurs were represented by two groups and other pterosaurs. They glide quite skillfully in the air, but in order to take to the skies, they needed to climb to impressive heights. These, for the most part, were not very mobile specimens of ancient mammals, but from the air they could very successfully track and attack prey in a pack method. Smaller representatives of flying dinosaurs preferred to make do with carrion.

In Jurassic sediments, the remains of a fledgling archaeopteryx lizard, which has long been considered by scientists to be the ancestor of birds, were found. But, as was recently scientifically proven, this species of lizard was a dead end. Birds evolved mainly from other species of reptiles. Archeopteryx had a long feathered tail, jaws studded with small teeth, and the feathered wings had developed fingers, with the help of which the animal grabbed branches. Archeopteryx flew poorly, mainly gliding from branch to branch. Basically, they preferred to climb tree trunks, digging into their bark and branches with the help of sharp curved claws. It is noteworthy that in our time only the chicks of the hoatzin bird have fingers on their wings.

The first birds, represented by small dinosaurs, jumped high either in an attempt to reach insects fluttering in the sky, or in order to escape from predators. In the process of evolution, they became more and more feathered, their jumps became longer and longer. During the jumping process, the future birds helped themselves more and more intensively by waving their forelimbs. Over time, their now wings, and not just forelimbs, acquired more and more powerful muscles, and the structure of their bones became hollow, as a result of which total weight birds became much easier. And all this led to the fact that by the end of the Jurassic period, the air space of the Jurassic, along with pterosaurs, was plowed by a large number of all kinds of ancient birds.

During the Jurassic period, small mammals also actively reproduced. But still they were not allowed to express themselves widely, since the ubiquitous power of dinosaurs was too overwhelming.

Since, during the process of climate change, the vast deserts of the Triassic began to be abundantly irrigated by precipitation, this created the preconditions for the advancement of vegetation further into the continents, and closer to the middle of the Jurassic period, almost the entire surface of the continents was covered with lush vegetation.

All low-lying places are abundantly overgrown with ferns, cycads and coniferous thickets. The sea coasts were occupied by araucarias, thujas and, again, cycads. Also, vast land masses were occupied by ferns and horsetails. Despite the fact that by the beginning of the Jurassic period the vegetation on the continents of the northern hemisphere was relatively uniform, by the middle of the Jurassic two already established and strengthened main belts of vegetation massifs were formed - northern and southern.

Northern belt was notable for the fact that at that time it was formed mainly by ginkgo plants mixed with herbaceous ferns. With all that half all vegetation northern latitudes Jurassic period consisted of varieties of ginkgo, today only one species of these plants has miraculously survived.

Southern belt were mainly cycads and tree ferns. At all Jurassic plants(Fig. 3) more than half still consisted of various ferns. Horsetails and mosses of those times were almost no different from today. In those places where cordaite and ferns grew en masse during the Jurassic period, tropical cycad jungles now grow. Of the gymnosperms, cycads were the most common in the Jurassic. Nowadays they can be found only in tropical and subtropical zones. It was these, with their crowns reminiscent of modern palm trees, that most herbivorous dinosaurs fed on.

Rice. 3 - Plants of the Jurassic period

In the Jurassic period, deciduous ginkgos first began to appear in northern latitudes. And in the second half of the period, the first spruce and cypress trees appeared. Jurassic coniferous forests were very similar to modern ones.

Minerals of the Jurassic period

The most pronounced mineral resources dating back to the Jurassic period are European and North American chromite deposits, Caucasian and Japanese copper-pyrite deposits, Alpine deposits of manganese ores, tungsten ores of the Verkhoyansk-Chukotka region, Transbaikalia, Indonesia, and the North American Cordillera. Also to this era can be attributed deposits of tin, molybdenum, gold and other rare metals scattered throughout, formed in the late Cimmerian era and thrown to the surface as a result of granitoid mechanisms associated with the separation of continents that took place at the end of the Jurassic period. Iron ore deposits are numerous and widespread. There are uranium ore deposits on the Colorado Plateau.

Eras. Lasted for 56 million years. Began 201 million years ago and ended 145 million years ago. The geochronological scale of the history of the Earth of all eons, eras and periods is located.

The name “Jura” was given by the name of the mountain range of the same name in Switzerland and France, where deposits of this period were first discovered. Later, geological strata of the Jurassic period were discovered in many other places on the planet.

During the Jurassic period, the Earth almost completely recovered from the largest in history. Various life forms - marine organisms, land plants, insects and many animal species - begin to flourish and increase their species diversity. In the Jurassic period, dinosaurs reigned - large, and sometimes simply gigantic lizards. Dinosaurs existed almost anywhere and everywhere - in the seas, rivers and lakes, in swamps, forests, and open spaces. Dinosaurs have become so diverse and widespread that over millions of years of evolution, some of them began to differ radically from each other. Dinosaurs included both herbivores and carnivores. Some of them were the size of a dog, while others reached a height of more than ten meters.

One of the species of lizards in the Jurassic period became the ancestor of birds. Archeopteryx, which existed just at this time, is considered an intermediate link between reptiles and birds. In addition to lizards and giant dinosaurs, warm-blooded mammals already lived on earth. Mammals of the Jurassic period were mostly small in size and occupied rather insignificant niches in the living space of the earth of those times. Against the background of the prevailing number and diversity of dinosaurs, they were practically invisible. This will continue throughout the Jurassic and subsequent periods. Mammals will become the rightful masters of the Earth only after the Cretaceous-Paleogene extinction, when all dinosaurs disappear from the face of the planet, opening the way for warm-blooded animals.

Animals of the Jurassic period

Allosaurus

Apatosaurus

Archeopteryx

Barosaurus

Brachiosaurus

Diplodocus

Dryosaurs

Giraffatitan

Camarasaurus

Camptosaurus

Kentrosaurus

Liopleurodon

Megalosaurus

Pterodactyls

Rhamphorhynchus

Stegosaurus

Scelidosaurus

Ceratosaurus

To protect your home or property, you must use best systems security. Alarm systems can be found at http://www.forter.com.ua/ohoronni-systemy-sygnalizatsii/. In addition, here you can purchase intercoms, video cameras, metal detectors and much more.

160 million years ago rich vegetable world provided food for the giant sauropods that had emerged by this time, and also provided shelter for a huge number of small mammals and lizards. At this time, conifers, ferns, horsetails, tree ferns and cycads were widespread.

A distinctive feature of the Jurassic period was the appearance and flourishing of giant lizard-hipped herbivorous dinosaurs, sauropods, the largest land animals that ever existed. Despite their size, these dinosaurs were quite numerous.

Their fossilized remains are found on all continents (except Antarctica) in rocks from the Early Jurassic to the Late Cretaceous, although they were most common in the second half of the Jurassic. At the same time, sauropods reach their largest sizes. They survived until the Late Cretaceous, when the huge hadrosaurs ("duck-billed dinosaurs") began to dominate the terrestrial herbivores.

Externally, all sauropods looked similar to each other: with an extremely long neck, an even longer tail, a massive but relatively short body, four column-like legs and a relatively small head. U various types Only the position of the body and the proportions of individual parts could change. For example, such sauropods of the Late Jurassic period as brachiosaurs (Brachiosaurus - “shouldered lizard”) were higher in the shoulder girdle than in the pelvic girdle, while contemporary diplodocus (Diplodocus - “double appendage”) were significantly lower, and at the same time their hips rose above their shoulders. Some sauropod species, such as Camarasaurus ("chamber lizard"), had a relatively short neck, only slightly longer than the body, while others, such as diplodocus, had a neck more than twice as long as the body.

Teeth and diet

The external similarity of sauropods masks the unexpectedly wide diversity in the structure of their teeth and, consequently, in their feeding methods.

The Diplodocus skull helped paleontologists understand the feeding method of this dinosaur. The abrasion of the teeth indicates that he plucked leaves either from below or from above him.

Many books on dinosaurs used to mention the "small, thin teeth" of sauropods, but it is now known that the teeth of some of them, such as Camarasaurs, were massive and strong enough to grind even very hard plant food, while the long and thin ones Diplodocus's pencil-shaped teeth do appear unable to withstand the significant stress of chewing hard plants.

diplodocus (Diplodocus). Its long neck allowed it to “comb” food from the tallest coniferous plants. It is believed that Diplodocus lived in small herds and ate tree shoots.

In a study of diplodocus teeth carried out in last years in England, unusual wear on their side surfaces was discovered. This pattern of tooth wear provided the key to understanding how these huge animals could feed. The side surface of the teeth could only wear down if something moved between them. Apparently, Diplodocus used its teeth to tear apart tufts of leaves and shoots, acting as a comb, while its lower jaw could move slightly back and forth. Most likely, when the animal stripped plants captured below by moving its head up and back, the lower jaw was moved back (the upper teeth were located in front of the lower ones), and when it pulled the branches of tall trees located above down and back, it pushed the lower jaw forward (the lower teeth were in front of the upper teeth).

Brachiosaurus probably used its shorter, slightly pointed teeth to pluck only high-lying leaves and shoots, since the vertical orientation of its body, due to the longer front legs, made it difficult to feed on plants growing low above the soil.

Narrow specialization

Camarasaurus, somewhat smaller in size than the giants mentioned above, had a relatively short and thicker neck and most likely fed on leaves located at an intermediate height between the feeding levels of brachiosaurs and diplodocus. It had a tall, rounded and more massive skull compared to other sauropods, as well as a more massive and stronger lower jaw, indicating a better ability to grind hard plant food.

The details of the anatomical structure of sauropods described above show that within the same ecological system (in the forests that covered most of the land at that time), sauropods ate different plant foods, obtaining them differently at different levels. This division by feeding strategy and type of food, which can be seen in herbivore communities today, is called “tropical partitioning.”

Brachiosaurus reached more than 25 m in length and 13 m in height. Their fossilized remains and fossilized eggs are found in East Africa and North America. They probably lived in herds like modern elephants.

The main difference between today's herbivore ecosystems and those of the Late Jurassic, which were dominated by sauropods, concerns only the mass and height of the animals. No modern herbivores, including elephants and giraffes, reach a height comparable to that of most large sauropods, and no modern land animals require such heights. great amount food like these giants.

The other end of the scale

Some sauropods that lived in the Jurassic period reached fantastic sizes, for example, the brachiosaurus-like Supersaurus, whose remains were found in the USA (Colorado), probably weighed about 130 tons, that is, it was many times larger than a large male African elephant. But these supergiants shared land with tiny creatures hiding underground that did not belong to dinosaurs or even reptiles. The Jurassic period was a time of existence of numerous ancient mammals. These small, furred, viviparous, milk-feeding warm-blooded animals were called multitubercular because of the unusual structure of their molars: numerous cylindrical “tubercles” fused together to form uneven surfaces, perfectly adapted to grinding plant food.

Polytubercles were the largest and most diverse group of mammals of the Jurassic and Cretaceous periods. They are the only omnivorous mammals of the Mesozoic era (the others were specialized insectivores or carnivores). They are known from Late Jurassic deposits, but recent finds show that they are close to a little-known group of extremely ancient mammals of the Late Triassic, the so-called. Haramides.

The structure of the skull and teeth was very similar to today's rodents; they had two pairs of protruding incisors, giving them the appearance of a typical rodent. Behind the incisors there was a gap that did not contain teeth, followed by molars to the very end of the small jaws. However, the multitubercle teeth closest to the incisors had an unusual structure. In fact, these were the first false-rooted (premolar) teeth with curved sawtooth edges.

This unusual dental structure has reappeared in the process of evolution in some of the modern marsupials, for example, in the rat kangaroos of Australia, whose teeth are of the same shape and located in the same place in the jaw as the false-rooted teeth of polytubercles. When chewing food at the moment of closing the jaws, multituberculates could move the lower jaw back, moving these sharp saw-toothed teeth across the food fibers, and the long incisors could be used to pierce dense plants or the hard exoskeletons of insects.

A saurian megalosaurus (Megalosaurus) and its young that overtook an ornithischian scelidosaurus (Scelidosaurus). Scelidosaurus is an ancient species of dinosaur of the Jurassic period with unevenly developed limbs, reaching 4 m in length. Its dorsal shell helped protect itself from predators.

The combination of sharp front incisors, serrated blades and chewing teeth means that the feeding apparatus of multitubercles was quite versatile. Today's rodents are also a very successful group of animals, thriving in a wide variety of ecological systems and habitats. Most likely, it was the highly developed dental apparatus, which allows them to eat a variety of foods, that became the reason for the evolutionary success of multitubercles. Their fossilized remains, found on most continents, belong to different species: some of them apparently lived in trees, while others, reminiscent of modern gerbils, were probably adapted to exist in arid desert climates.

Changing Ecosystems

The existence of multitubercles covers a period of 215 million years, extending from the Late Triassic through the entire Mesozoic era before the Oligocene epoch Cenozoic era. This phenomenal success, unique among mammals and most terrestrial tetrapods, makes polytubercles the most successful group of mammals.

Small animal ecosystems of the Jurassic period also included small lizards of a wide variety of species and even their aquatic forms.

Thrinadoxon (cynodont species). Its limbs protruded slightly to the sides, and were not located under the body, as in modern mammals.

They and the rarely encountered reptiles of the group of synapsids (“beast-like reptiles”), tritylodonts, who survived to this time, lived at the same time and in the same ecosystems as polytubercular mammals. Tritylodonts were numerous and widespread throughout the Triassic period, but, like other cynodonts, suffered greatly during the Late Triassic extinction event. They are the only group of cynodonts to survive into the Jurassic period. By appearance they, like multitubercular mammals, closely resembled modern rodents. That is, a significant part of the ecosystems of small animals of the Jurassic period consisted of animals resembling rodents: trilodonts and polytubercular mammals.

Polytuberculates were by far the most numerous and diverse group of mammals of the Jurassic period, but other groups of mammals existed at this time, including: morganacodonts (the oldest mammals), amphilestids (peramurids), amphitherids (amphitherids), tynodonts ( tinodontids) and docodonts.

All these small mammals looked like mice or shrews. Docodonts, for example, developed distinctive, wide molars well suited for chewing hard seeds and nuts. At the end of the Jurassic period, significant changes occurred at the other end of the size scale in the group of large bipedal predatory dinosaurs, theropods, represented at this time by allosaurs (AUosaurus - “strange lizards”). At the end of the Jurassic period, a group of theropods became isolated, called spinosaurids (“spiny or spiny lizards”). distinctive feature

which had a crest of long processes of the trunk vertebrae, which, perhaps, like the dorsal sail of some pelycosaurs, helped them regulate body temperature. Spinosaurids such as Siamosaurus (“lizard from Siam”), which reached a length of 12 m, along with other theropods shared the niche of the largest predators in the ecosystems of that time.

Spinosaurids had non-serrated teeth and elongated, less massive skulls compared to other theropods of this time. These structural features indicate that they differed in their feeding method from such theropods as allosaurs, Eustreptospondylus (“highly curved vertebrae”) and ceratosaurs (Ceratosaurus - “horned lizard”), and most likely hunted other prey.

In Late Jurassic time, other types of theropods arose, very different from such huge, weighing up to 4 tons, predators as allosaurus. These were ornithominids - long-legged, long-necked, small-headed, toothless omnivores, strikingly reminiscent of modern ostriches, which is why they got their name “bird imitators”.

The earliest ornithominid, Elaphrosaums ("light lizard"), from the Late Jurassic deposits of North America had light, hollow bones and a toothless beak, and its limbs, both hind and forelimbs, were shorter than those of later Cretaceous ornithominids, and, accordingly, it was a slower animal.

Another ecologically important group of dinosaurs that arose in the Late Jurassic are the nodosaurs, four-legged dinosaurs with massive, shell-covered bodies, short, relatively thin limbs, a narrow head with an elongated snout (but with massive jaws), small leaf-shaped teeth, and a horny beak. Their name (“knobby lizards”) is associated with the bony plates covering the skin, protruding processes of the vertebrae and growths scattered across the skin, which served as protection from attacks by predators. Nodosaurs became widespread only in the Cretaceous period, and in the Late Jurassic they, along with huge tree-eating sauropods, were only one of the elements of a community of herbivorous dinosaurs that served as prey for a number of huge predators.