Jurassic period of the Mesozoic era. Jurassic period, description of the Jurassic period, dinosaurs of the Jurassic period, lizards of the Jurassic period Where is the Jurassic period located
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 Jurassic period caused sea transgression. The continents were divided and the climate in Jurassic period Jurassic period
became wetter than in the Triassic. On the site of deserts of the Triassic period, in Jurassic period lush vegetation grew. Huge areas were covered with lush vegetation. Forests consisted mainly of ferns and gymnosperms., about 195 million years ago Throughout the northern hemisphere, the vegetation was quite monotonous. But already starting from the middle of the Jurassic period, about 170-165 million years ago, two (conditional) plant belts were formed: northern and southern. The northern plant belt was dominated by ginkgo and herbaceous ferns. Jurassic period IN
ginkgos were very widespread. Groves of ginkgo trees grew throughout the belt.
The southern plant belt was dominated by cycads and tree ferns. Jurassic period 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 consisted mainly of ferns and gymnosperms. now occupied by tropical forests, consisting mainly of cycads. Cycads are 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 they were even initially identified as palm trees in the plant system. Jurassic period 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
were similar to modern ones. Land animals
Jurassic period: 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.
Diversity of dinosaur species in Jurassic period it was great. They could be the size of a cat or chicken, or they could reach the size of huge whales. One of the fossil creatures, 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:
IN Jurassic period Winged lizards - pterosaurs - reigned supreme in the air. They appeared in the Triassic, but their heyday was precisely Jurassic period Pterosaurs were represented by two groups pterodactyls And Rhamphorhynchus .
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.
. 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. 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 The population of the seabed has changed greatly. Bivalves displace brachiopods from shallow waters. Brachiopod shells are replaced by oysters. consisted mainly of ferns and gymnosperms. 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 Jurassic climate and vegetation: Other important events also took place. IN
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. The resulting giant coral reefs sheltered numerous ammonites and new species of belemnites (old relatives of today's octopuses and squids). Jurassic period They also housed many invertebrates, such as sponges and bryozoans (sea mats). Gradually, fresh sediment accumulated on the seabed.
On land, in lakes and rivers
There were many different species of crocodiles that spread widely 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. The tail fins allowed them to develop greater speed in the water than on land.
Jurassic period: New species of sea turtles have also appeared. All dinosaurs of the Jurassic period Herbivorous dinosaurs:
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- 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.
Jurassic period: | 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). | |
Departments | ||
tiers | ||
Leias (Lower) | ||
Hettangian | Sinemyursky | |
Pliensbachian | ||
Toarsky | ||
Dogger (Medium) | ||
Aalensky | Bayocian | |
Bathian | ||
Callovian |
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 of modern Europe. It originated from the Iberian Peninsula and, crossing the south and southeast of Asia diagonally, entered the 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.
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, also received an impetus for their development. 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 were replenished with new varieties of dragonflies, beetles, cicadas, bugs, etc. Along with the emergence of a huge number of flowering plants, a large number of pollinating insects began to appear, feeding 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(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.
There were also smaller predators, for example, such as 3-meter dilophosaurs, weighing only 400 kg, but flocking together, they attacked even larger predators.
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, the animal world of the 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 caused the extinction of dinosaurs in the Cretaceous period is still not known.
By the mid-Jurassic period, the airspace was filled with many flying dinosaurs such as pterodactyls 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 wings, and not just their forelimbs, acquired increasingly powerful muscles, and the structure of their bones became hollow, as a result of which the overall weight of the birds became much lighter. 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.
Jurassic geological period, Jura, 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 wide 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.
During the Jurassic period, groves of ginkgo trees grew throughout the then temperate zone. Ginkgos are deciduous (unusual for gymnosperms) trees with an oak-like crown and small fan-shaped leaves. Only one species has survived to this day - Ginkgo biloba. Conifers were very diverse, similar to modern pines and cypresses, which flourished at that time not only in the tropics, but had already mastered the temperate zone.
Marine organisms
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.
And was replaced by chalk, and had a duration of about 56 million years.
Geography and climate
During the Jurassic period, the supercontinent Pangea began to split into two separate continents:
- the northern part known as Laurasia (which eventually split into North America and Eurasia, opening basins to the Atlantic Ocean and the Gulf of Mexico)
- the southern part - Gondwanaland - drifted east (and eventually divided into Antarctica, Madagascar, India and Australia, and its western part formed Africa and South America).
This process of Pangea's separation, along with warmer global temperatures, allowed reptiles such as dinosaurs to diversify and dominate the Earth for long periods of time.
Plant life
During the Mesozoic era, plants developed the ability to lead a terrestrial lifestyle and not be limited only to the oceans. By the beginning of the Jurassic, life came from bryophytes, low-growing bryophytes and liverworts, which had no vascular tissue and were limited to wet, marshy areas.
Ginkgo trees
Ferns and gingaceae, which had roots and vascular tissue for transporting water and nutrients, and reproduced by spores, were the dominant plants of the Early Jurassic. During the Jurassic period, a new way of plant reproduction appeared. Gymnosperms, such as conifers, have evolved pollen that is dispersed over long distances by the wind to pollinate female cones. This method of reproduction made it possible to significantly increase the number of gymnosperms by the end of the Jurassic period. Flowering plants did not evolve until the Cretaceous period.
Age of Dinosaurs
As depicted in the movie Jurassic Park, reptiles were the dominant animal life form during the Jurassic period. They overcame evolutionary obstacles that limited . Reptiles had strong, ossified skeletons with advanced muscular systems to support and move the body. Some of the largest animals that ever lived were the dinosaurs of the Jurassic period. Reptiles could also develop amniotic eggs that were incubated on land.
sauropods
Sauropods (lizard-footed dinosaurs) are herbivorous quadrupeds with long necks and heavy tails. Many sauropods, such as brachiosaurs, were huge. Representatives of some genera had a body length of about 25 m, and weight ranged from 50-100 tons, which makes them the largest land animals that have ever existed on Earth. Their skulls were relatively small, with nostrils raised high towards the eyes. Such small skulls meant very small brains. Despite their small brains, this group of animals flourished during the Jurassic period and had a wide geographic distribution. Sauropod fossils have been found on every continent except Antarctica. Other famous Jurassic dinosaurs include stegosaurs and flying pterosaurs.
Carnosaurs were one of the main predators of the Mesozoic era. The genus Allosaurus was one of the most widespread carnosaurs in North America. They are similar to later tyrannosaurs, although studies have shown that they have little in common. Allosaurs had strong hind limbs, heavy front legs and long jaws.
Early mammals
Adelobazilevs
Dinosaurs may have been the dominant land animals, but they were not the only fauna. Early mammals were mostly very small herbivores or insectivores, and did not compete with larger reptiles. Adelobasileus is a predatory ancestor of mammals. He had a special structure of the inner ear and jaws. This animal appeared at the end of the Triassic period.
In August 2011, scientists from China announced the discovery of Yuramaya. This tiny mid-Jurassic animal caused excitement among scientists because it was a clear ancestor of placental mammals, indicating that mammals evolved much earlier than previously thought.
Sea life
Plesiosaur
The Jurassic period was also very diverse. The largest marine predators were plesiosaurs. These carnivorous marine reptiles typically had wide bodies and long necks with four flipper-shaped limbs.
Ichthyosaur is a marine reptile that was most common in the Early Jurassic period. Because some fossils have been found with smaller individuals of their species inside their bodies, it is suggested that these animals may have been among the first to experience internal pregnancy and give birth to live young.
Cephalopods were also widespread during the Jurassic period and included the ancestors of modern squids. Among the most beautiful fossils of marine life are the spiral-shaped shells of ammonites.
, conglomerates formed in a variety of conditions.
Jurassic System Division
The Jurassic system is divided into 3 divisions and 11 tiers:
system | Department | tier | Age, million years ago | |
---|---|---|---|---|
Chalk | Lower | Berriasian | less | |
Yura | Upper (malm) |
Titonian | 152,1-145,0 | |
Kimmeridge | 157,3-152,1 | |||
Oxford | 163,5-157,3 | |||
Average (dogger) |
Callovian | 166,1-163,5 | ||
Bathian | 168,3-166,1 | |||
Bayocian | 170,3-168,3 | |||
Aalensky | 174,1-170,3 | |||
Lower (lias) |
Toarsky | 182,7-174,1 | ||
Pliensbachian | 190,8-182,7 | |||
Sinemyursky | 199,3-190,8 | |||
Hettangian | 201,3-199,3 | |||
Triassic | Upper | Rhetic | more | |
Divisions are given according to IUGS as of April 2016 |
Geological events
213-145 million years ago, 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).
Vegetation
During the Jurassic, vast areas were covered with lush vegetation, primarily diverse forests. They mainly consisted of ferns and gymnosperms.
Land animals
One of the fossil creatures that combines 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 work "On the Origin of Species" and became a strong argument in favor of the theory of evolution - it was initially considered a transitional form from reptiles to birds (in fact, it was a dead-end branch of evolution, not directly related to real birds) . Archeopteryx flew rather 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. During the Jurassic period, the division of mammals into monotremes, marsupials and placentals occurred.
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Notes
Literature
- Iordansky N. N. Development of life on earth. - M.: Education, 1981.
- Karakash N. I. ,. Jurassic system and period // Encyclopedic Dictionary of Brockhaus and Efron: in 86 volumes (82 volumes and 4 additional). - St. Petersburg. , 1890-1907.
- Koronovsky N.V., Khain V.E., Yasamanov N.A. Historical geology: Textbook. - M.: Academy, 2006.
- Ushakov S.A., Yasamanov N.A. Continental drift and climates of the Earth. - M.: Mysl, 1984.
- Yasamanov N.A. Ancient climates of the Earth. - L.: Gidrometeoizdat, 1985.
- Yasamanov N.A. Popular paleogeography. - M.: Mysl, 1985.
Links
- - Site about the Jurassic period, a large library of paleontological books and articles.
← | P A l e O h O th |
Mesozoic (252.2-66.0 million years ago) | TO A th n O h O th |
→ | ||
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← | Triassic (252,2-201,3) |
Jurassic period: (201,3-145,0) |
Cretaceous period (145,0-66,0) |
→ |
An excerpt characterizing the Jurassic period
The trees stood bare and featureless, lazily moving their drooping, thorny branches. Further behind them stretched the joyless, burnt-out steppe, getting lost in the distance behind a wall of dirty, gray fog... Many gloomy, drooping human beings restlessly wandered back and forth, senselessly looking for something, not paying any attention to the world around them, which, and however, it did not evoke the slightest pleasure so that one would want to look at it... The whole landscape evoked horror and melancholy, seasoned with hopelessness...“Oh, how scary it is here...” Stella whispered, shuddering. – No matter how many times I come here, I just can’t get used to it... How do these poor things live here?!
– Well, probably these “poor things” were too guilty once if they ended up here. Nobody sent them here - they just got what they deserved, right? – still not giving up, I said.
“But now you’ll look...” Stella whispered mysteriously.
A cave overgrown with grayish greenery suddenly appeared in front of us. And out of it, squinting, came a tall, stately man who in no way fit into this wretched, soul-chilling landscape...
- Hello, Sad! – Stella greeted the stranger affectionately. - I brought my friend! She doesn't believe that good people can be found here. And I wanted to show you to her... You don’t mind, do you?
“Hello, dear...” the man answered sadly, “But I’m not that good to show off to anyone.” You're wrong...
Oddly enough, I actually immediately liked this sad man for some reason. He exuded strength and warmth, and it was very pleasant to be around him. In any case, he was in no way like those weak-willed, grief-stricken people who surrendered to the mercy of fate, with whom this “floor” was chock-full.
“Tell us your story, sad man...” Stella asked with a bright smile.
“There’s nothing to tell, and there’s nothing particularly to be proud of...” the stranger shook his head. - And what do you need this for?
For some reason, I felt very sorry for him... Without knowing anything about him, I was already almost sure that this man could not have done anything truly bad. Well, I just couldn’t!.. Stela, smiling, followed my thoughts, which she apparently really liked...
“Well, okay, I agree - you’re right!..” Seeing her happy face, I finally honestly admitted.
“But you don’t know anything about him yet, but with him everything is not so simple,” Stella said, smiling slyly and contentedly. - Well, please tell her, Sad...
The man smiled sadly at us and said quietly:
– I’m here because I killed... I killed many. But it was not out of desire, but out of need...
I was immediately terribly upset - he killed!.. And I, stupid, believed it!.. But for some reason I stubbornly did not have the slightest feeling of rejection or hostility. I clearly liked the person, and no matter how hard I tried, I couldn’t do anything about it...
- Is it really the same guilt - to kill at will or out of necessity? – I asked. – Sometimes people have no choice, do they? For example: when they have to defend themselves or protect others. I have always admired heroes - warriors, knights. I generally always adored the latter... Is it possible to compare simple murderers with them?
He looked at me for a long time and sadly, and then also quietly answered:
- I don’t know, dear... The fact that I am here says that the guilt is the same... But the way I feel this guilt in my heart, then no... I never wanted to kill, I just defended my land, I was a hero there... But here it turned out that I was just killing... Is this right? I think no...
- So you were a warrior? – I asked hopefully. - But then, this is a big difference - you defended your home, your family, your children! And you don’t look like a murderer!..
- Well, we are all not like the way others see us... Because they see only what they want to see... or only what we want to show them... And about the war - I also first just as you thought, you were even proud... But here it turned out that there was nothing to be proud of. Murder is murder, and it doesn’t matter how it was committed.
“But this is not right!..” I was indignant. - What happens then - a maniac-killer turns out to be the same as a hero?!.. This simply cannot be, this should not happen!
Everything inside me was raging with indignation! And the man sadly looked at me with his sad, gray eyes, in which understanding was read...
“A hero and a murderer take lives in the same way.” Only, probably, there are “extenuating circumstances,” since a person protecting someone, even if he takes a life, does so for a bright and righteous reason. But, one way or another, they both have to pay for it... And it’s very bitter to pay, believe me...
– Can I ask you how long ago you lived? – I asked, a little embarrassed.
- Oh, quite a long time ago... This is the second time I’m here... For some reason, my two lives were similar - in both of them I fought for someone... Well, and then I paid... And it’s always just as bitter ... – the stranger fell silent for a long time, as if not wanting to talk about it anymore, but then he quietly continued. – There are people who love to fight. I always hated it. But for some reason, life is returning me to the same circle for the second time, as if I was locked in this, not allowing me to free myself... When I lived, all our peoples fought among themselves... Some seized foreign lands - others they defended the lands. Sons overthrew fathers, brothers killed brothers... Anything happened. Someone accomplished unimaginable feats, someone betrayed someone, and someone turned out to be simply a coward. But none of them even suspected how bitter the payment would be for everything they had done in that life...
– Did you have family there? – to change the subject, I asked. - Were there children?
- Certainly! But that was already so long ago!.. They once became great-grandfathers, then they died... And some are already living again. That was a long time ago...
“And you’re still here?!..” I whispered, looking around in horror.
I couldn’t even imagine that he had been existing here like this for many, many years, suffering and “paying” his guilt, without any hope of leaving this terrifying “floor” even before the time came for him to return to the physical Earth!.. And there he will again have to start all over again, so that later, when his next “physical” life ends, he will return (perhaps here!) with a whole new “baggage”, bad or good, depending on how he will live his “next” earthly life... And he could not have any hope of freeing himself from this vicious circle (be it good or bad), since, having begun his earthly life, each person “dooms” himself to this endless, an eternal circular “journey”... And, depending on his actions, returning to the “floors” can be very pleasant, or very scary...