Encyclopedic short information about the Jurassic period. Jurassic period

From 213 to 144 million years ago.
By the beginning of the Jurassic period, the giant supercontinent Pangea was in the process of active decay. South of the equator, there was still a single vast mainland, which was again called Gondwana. Later it also split into parts that formed today's Australia, India, Africa and South America. land animals northern hemisphere could no longer move freely from one continent to another, but they still spread freely throughout the southern supercontinent.
At the beginning of the Jurassic period, the climate throughout the Earth was warm and dry. Then, as heavy rains began to soak the ancient Triassic deserts, the world became greener again, with more lush vegetation. In the Jurassic landscape, horsetails and club mosses grew thickly, which survived from the Triassic period. Palm-shaped bennettites have also been preserved. In addition, there were many griots around. Extensive forests of seed, common and tree ferns, as well as fern-like cycads, spread from water bodies inland. were still common coniferous forests. In addition to ginkgo and araucaria, the ancestors of modern cypresses, pines and mammoth trees grew in them.

Life in the seas.

As Pangea began to split apart, new seas and straits arose, in which new types of animals and algae found refuge. Gradually on seabed accumulated fresh sediments. Many invertebrates settled in them, such as sponges and bryozoans (sea mats). In warm and shallow seas, other important events. Giant coral reefs formed there, sheltering numerous ammonites and new varieties of belemnites (old relatives of today's octopuses and squids).
On land, in lakes and rivers, many different types crocodiles, widely dispersed around 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 it easier to swim. Tail fins allowed them to reach greater speed in water than on land. There are also new types sea ​​turtles. Evolution also gave rise to many species of plesiosaurs and ichthyosaurs that competed with new, fast-moving sharks and extremely mobile bony fish.

This cycad is a living fossil. It almost does not differ from its relatives that grew on Earth in the Jurassic period. Now cycads are found only in the tropics. However, 200 million years ago they were much more widespread.
Belemnites, living projectiles.

Belemnites were close relatives of modern cuttlefish and squid. They had a cigar-shaped internal skeleton. Its main part, consisting of a calcareous substance, is called the rostrum. At the anterior end of the rostrum there was a cavity with a fragile multi-chambered shell, which helped the animal to stay afloat. This entire skeleton was placed inside the soft body of the animal and served as a solid frame to which its muscles were attached.
The solid rostrum is best preserved in fossil form than any other body part of a belemnite, and it is usually this that falls into the hands of scientists. But sometimes, non-roster fossils are also found. The first such finds at the beginning of the XIX century. baffled many experts. They guessed that they were dealing with the remains of belemnites, but without the accompanying rostrum, these remains looked rather strange. The answer to this mystery turned out to be extremely simple, as soon as more data was collected about the way the ichthyosaurs feed - the main enemies of the belemnites. Apparently, rostless fossils were formed when an ichthyosaur swallowed a whole school of belemnites and regurgitated the soft parts of one of the animals, while its hard internal skeleton remained in the stomach of a predator.
Belemnites, like modern octopuses and squids, developed an inky liquid and used it to create a "smoke screen" when they tried to escape from predators. Scientists have also discovered fossilized belemnite ink sacs (organs in which a supply of ink liquid was stored). One of the scientists of the Victorian era, William Buckland, even managed to extract some of the ink from fossil ink bags, which he used to illustrate his book Bridgewater Treatise.

Plesiosaurs, barrel-shaped marine reptiles with four wide flippers, with which they rowed in the water like oars.
Glued fake.

No one has yet been able to find a whole fossil belemnite (soft part plus rostrum), although in the 70s. 20th century in Germany, a rather ingenious attempt was made to fool the whole scientific world with a clever forgery. Whole fossils, allegedly taken from a quarry in southern Germany, were purchased by several museums at a very high price, before it was discovered that in all cases the calcareous rostrum was carefully glued to the fossil soft parts of the belemnites!
This famous photograph, taken in 1934 in Scotland, was recently declared a fake. Nevertheless, for fifty years it fueled the enthusiasm of those who considered the Loch Ness monster to be a living plesiosaur.

Mary Anning (1799 - 1847) was only 2 years old when she discovered the first ichthyosaur fossil at Lyme Regis in Dorothy, England. Subsequently, she was lucky to find also the first fossil skeletons of a plesiosaur and a pterosaur.
This child could find
Glasses, pins, nails.
But got in the way
Ichthyosaurus bones.

Born for Speed

The first ichthyosaurs appeared in the Triassic. These reptiles were ideally adapted to life in the shallow seas of the Jurassic period. They had a streamlined body, fins of various sizes and long narrow jaws. The largest of them reached a length of about 8 m, but many species did not exceed a person in size. They were excellent swimmers, feeding mainly on fish, squid and nautiloids. Although ichthyosaurs belonged to reptiles, their fossil remains suggest that they were viviparous, that is, they produced ready-made offspring, like mammals. Perhaps the young ichthyosaurs were born in the open sea, like whales.
Another group of predatory reptiles, also widespread in Jurassic seas, - plesiosaurs. Their long-necked varieties lived near the surface of the sea. Here they hunted for shoals of very large fish with their flexible necks. Short-necked species, the so-called pliosaurs, preferred life at great depths. They ate ammonites and other molluscs. Some large pliosaurs appear to have preyed on smaller plesiosaurs and ichthyosaurs as well.

Ichthyosaurs looked like exact copies of dolphins, except for the shape of the tail and an extra pair of fins. For a long time scientists believed that all the fossil ichthyosaurs that fell into their hands had a damaged tail. In the end, they guessed that the spine of these animals had a curved shape and at its end was a vertical tail fin (in contrast to the horizontal fins of dolphins and whales).
Life in the Jurassic air.

In the Jurassic period, the evolution of insects accelerated dramatically, and as a result, the Jurassic landscape eventually filled with endless buzzing and crackling, which were emitted by many new types of insects, crawling and flying everywhere. Among them were predecessors
modern ants, bees, earwigs, flies and wasps. Later, in the Cretaceous period, there was a new evolutionary explosion, when insects began to "make contacts" with the newly appeared flowering plants.
Until that time, real flying animals were found only among insects, although attempts to master the air environment were also observed in other creatures that learned to plan. Now whole hordes of pterosaurs have risen into the air. These were the first and largest flying vertebrates. Although the first pterosaurs appeared at the end of the Triassic, their true "rise" occurred precisely in the Jurassic period. Light skeletons of pterosaurs consisted of hollow bones. The first pterosaurs had tails and teeth, but in more highly developed individuals, these organs disappeared, which made it possible to significantly reduce their own weight. In some fossil pterosaurs, hair is guessed. Based on this, it can be assumed that they were warm-blooded.
Scientists still disagree about the lifestyle of pterosaurs. For example, it was originally believed that pterosaurs were a kind of "living gliders" that soared like vultures above the ground in the streams of rising hot air. Perhaps they even glided over the surface of the ocean, attracted sea ​​winds like modern albatrosses. However, now some experts believe that pterosaurs could flap their wings, that is, actively fly, like birds. Perhaps some of them even walked like a bird, while others dragged their bodies along the ground or slept in the nesting places of relatives, hanging upside down, like bats.

Data obtained from the analysis of the fossilized stomachs and dung (coprolites) of ichthyosaurs indicate that their diet consisted mainly of fish and cephalopods (ammonites, nautiloids and squids). The contents of the stomachs of ichthyosaurs made it possible to make an even more curious discovery. Small hard spikes on the tentacles of squid and other cephalopods, apparently, caused a lot of inconvenience to ichthyosaurs, since they were not digested and, accordingly, could not freely pass through them. digestive system. As a result, the spikes accumulated in the stomach, and from them scientists manage to find out what the animal ate throughout its life. So, when studying the stomach of one of the fossil ichthyosaurs, it turned out that he swallowed at least 1500 squids!
How birds learned to fly.

There are two main theories trying to explain how birds learned to fly. One of them claims that the first flights took place from the bottom up. According to this theory, it all began with the fact that bipedal animals, the predecessors of birds, ran and jumped high into the air. Perhaps this is how they tried to escape from predators, or maybe they caught insects. Gradually, the feathered area of ​​the "wings" became large, the jumps, in turn, lengthened. The bird did not touch the ground longer and remained in the air. Add to this the flapping movements of the wings - and it will become clear to you how, after a long time, these "pioneers of aeronautics" learned to stay in flight for a long time, and their wings gradually acquired properties that allowed them to support the body in the air.
However, there is another theory, the opposite, according to which the first flights took place from top to bottom, from trees to the ground. Potential "flyers" had to first climb to a considerable height, and only then throw themselves into the air. In this case, the first step on the way to flying should have been planning, since with this type of movement, energy costs are extremely insignificant - in any case, much less than with the "running-jumping" theory. The animal does not need to make additional efforts, because when planning it is pulled down by the force of the earth's gravity.

The first fossil Archeopteryx was discovered two years after the publication of Charles Darwin's On the Origin of Species. This important discovery was another confirmation of Darwin's theory that evolution is very slow and that one group of animals gives birth to another, undergoing a series of successive transformations. The famous scientist and close friend of Darwin, Thomas Huxley, predicted the existence of an animal like Archeopteryx in the past, even before its remains fell into the hands of scientists. In fact, Huxley described this animal in detail before it was discovered!
Step flight.

One scientist proposed an extremely curious theory. It describes a series of stages through which the "pioneers of aeronautics" had to pass in the course of the evolutionary process that eventually turned them into flying animals. According to this theory, once one of the groups of small reptiles, called pro-topts, switched to an arboreal way of life. Perhaps the reptiles climbed trees because it was safer there, or easier to get food, or more convenient to hide, sleep, equip nests. It was cooler on the treetops than on the ground, and these reptiles developed warm-bloodedness and feathers for better thermal insulation. Any extra long feathers on the limbs were welcome - they provided additional thermal insulation and increased the surface area of ​​the winged "arms".
In turn, soft, feathered forelimbs softened the impact on the ground when the animal lost balance and fell from tall tree. They slowed down the fall (acting as a parachute), and also provided a more or less soft landing, serving as a natural shock absorber. Over time, these animals began to use feathered limbs as proto-wings. Further transition from para-
from the late stage to the planning stage should have become a completely natural evolutionary step, after which it was the turn of the last, flight, stage, which Archeopteryx almost certainly reached.

"Early" bird
The first birds appeared on Earth towards the end of the Jurassic period. The most ancient of them, Archeopteryx, looked more like a small feathered dinosaur than a bird. She had teeth and a long bony tail adorned with two rows of feathers. Three clawed fingers protruded from each of its wings. Some scientists believe that Archeopteryx used its clawed wings to climb trees, from where it periodically flew back to the ground. Others believe that he lifted himself off the ground using gusts of wind. In the process of evolution, the skeletons of birds became lighter, and the toothy jaws were replaced by a toothless beak. They developed a "wide sternum, to which the powerful muscles necessary for flight were attached. All these changes made it possible to improve the structure of the bird's body, giving it an optimal structure for flight.
The first fossil find of Archeopteryx was a single feather, discovered in 1861. Soon, a whole skeleton of this animal (and with feathers!) was found in the same area. Since then, six fossilized skeletons of Archeopteryx have been discovered, some complete and others only fragmentary. The last such find dates back to 1988.

Age of dinosaurs.

The very first dinosaurs appeared over 200 million years ago. Over the 140 million years of their existence, they have evolved into a wide variety of species. Dinosaurs spread across all continents and adapted to life in a wide variety of habitats, although none of them lived in holes, did not climb trees, did not fly or swim. Some dinosaurs were no bigger than squirrels. Others weighed more than fifteen adult elephants combined. Some waddled heavily on all fours. Others ran faster on two legs than Olympic sprint champions.
65 million years ago, all dinosaurs suddenly became extinct. However, before disappearing from the face of our planet, they left us in the rocks a detailed "report" about their life and their time.
The most common group of dinosaurs in the Jurassic were the prosauropods. Some of them evolved into the largest land animals of all time - sauropods ("lizards"). These were the "giraffes" of the dinosaur world. They probably spent all their time eating leaves from the tops of trees. To provide vital energy for such a huge body, an incredible amount of food was required. Their stomachs were capacious digestive containers, continuously processing mountains of plant food.
Later, many varieties of small, swift-footed dinos appeared.
saurs - the so-called hadrosaurs. These were the "gazelles" of the dinosaur world. They plucked the undersized vegetation with their horny beaks and then chewed it up with strong molars.
The largest family of large carnivorous dinosaurs were the megalosaurids, or "huge lizards". The Megalosaurid was a ton-weight monster with huge, sharp, saw-toothed teeth that it used to tear through the flesh of its victims. Based on some of the fossilized footprints, his toes were pointing inward. It may have waddle like a giant duck, swinging its tail from side to side. Megalosaurids populated all areas the globe. Their fossils have been found in places as far apart as North America, Spain and Madagascar.
The early species of this family were, apparently, relatively small animals of a fragile constitution. And later megalosaurids became truly bipedal monsters. Their hind legs ended in three fingers armed with powerful claws. Muscular forelimbs helped in hunting large herbivorous dinosaurs. The sharp claws no doubt left horrific lacerations in the flank of the surprised prey. The powerful muscular neck of the predator allowed him to thrust his dagger-like fangs deep into the body of the prey with terrible force and pull out huge pieces of still warm meat from it.

In the Jurassic period, flocks of allosaurs robbed most of the earth's land. They, apparently, were a nightmarish sight: after all, each member of such a flock weighed more than a ton. Together, allosaurs could easily defeat even a large sauropod.

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 during the Jurassic period was highly variable.

From the Aalenian to the Bathan Age, the climate was warm and humid. Then there was a glaciation that occupied most of the Callovian, Oxfordian and early Kimmeridgian, and then the climate warmed up again.

Vegetation

In the Jurassic, vast areas were covered with lush vegetation, primarily a variety of forests. They mainly consisted of ferns and gymnosperms.

land animals

One of the fossil creatures that combine the features of birds and reptiles is Archeopteryx. For the first time, his skeleton was discovered in the so-called lithographic slates in Germany. The find was made two years after the publication of Charles Darwin's work " 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. But later it was also suggested that it was a dead end branch of evolution, not directly related to real birds. Archeopteryx flew rather poorly (planned from tree to tree), and was about the size of a crow. Instead of

The Jurassic period is the middle of the Mesozoic era. This piece of history is primarily famous for its dinosaurs, it was very good time for all living things. During the Jurassic period, for the first time, reptiles ruled everywhere: in water, on land and in the air.
This period was named after a mountain range in Europe. The Jurassic period began about 208 million years ago. This period was more revolutionary than the Triassic. This revolutionism was with those estates that happened with the earth's crust, because it was during the Jurassic period that the mainland of Pangea began to diverge. The climate has since become warmer and more humid. In addition, the level of water in the world's oceans began to rise. All this gave great opportunities for animals. Due to the fact that the climate became more favorable, plants began to appear on land. And corals began to appear in shallow waters.

The Jurassic period lasted from 213 to 144 million years ago. At the very beginning of the Jurassic period, the climate throughout the Earth was dry and warm. All around were deserts. But later heavy rains began to soak them with moisture. And the world became greener, lush vegetation began to flourish.
Ferns, conifers, and cycads formed extensive marshy forests. Araucaria, arborvitae, cicadas grew on the coast. Ferns and horsetails formed vast forest areas. At the beginning of the Jurassic period, about 195 million years ago. throughout the northern hemisphere, the vegetation was rather 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. Ginkgo and herbaceous ferns predominated in the northern vegetation belt. In the Jurassic period, Ginkgoaceae were very widespread. Groves of ginkgo trees grew throughout the belt.

In the southern vegetation belt, cycads and tree ferns predominated.
Ferns of the Jurassic period have survived to this day in some parts of the wild. Horsetails and club mosses almost did not differ from modern ones. Jurassic period ferns and cordaites are now occupied by tropical forests, consisting mainly of cycads. Cycads are a class of gymnosperms that dominated the green cover of the Jurassic Earth. Now they are found here and there in the tropics and subtropics. Dinosaurs roamed under the canopy of these trees. Outwardly, 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 the Jurassic, ginkgo trees 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 during the Jurassic period. The coniferous forests of the Jurassic period were similar to modern ones.

During the Jurassic period, a temperate climate was established on Earth. Even the arid zones were rich in vegetation. Such conditions were ideal for the reproduction of dinosaurs. Among them, lizards and ornithischians are distinguished.

Lizards moved on four legs, had five toes on their feet, and ate plants. Most of them had a long neck, a small head and a long tail. They had two brains: one small, in the head; the second is much larger in size - at the base of the tail.
The largest of jurassic dinosaurs there was a brachiosaurus, reaching a length of 26 m, weighing about 50 tons. It had columnar legs, a small head, and a thick long neck. Brachiosaurs lived on the shores of the Jurassic lakes, fed on aquatic vegetation. Every day, the brachiosaurus needed at least half a ton of green mass.
Diplodocus is the oldest reptile, its length was 28 m. It had a long thin neck and a long thick tail. Like a brachiosaurus, diplodocus moved on four legs, the hind legs were longer than the front ones. Diplodocus spent most of its life in swamps and lakes, where it grazed and escaped from predators.

Brontosaurus was comparatively tall, had a large hump on its back and a thick tail. Chisel-shaped small teeth were densely located on the jaws of a small head. The brontosaurus lived in swamps, on the shores of lakes. Brontosaurus weighed about 30 tons and exceeded 20 in length. Lizard-footed dinosaurs (sauropods) were the largest land animals known so far. All of them were herbivores. Until recently, paleontologists believed that such heavy creatures were forced to spend most of their lives in the water. It was believed that on land, his tibia would "break" under the weight of a colossal carcass. However, the finds recent years(in particular, footprints) indicate that sauropods preferred to roam in shallow water, they also entered solid ground. In relation to body size, brontosaurs had an extremely small brain, weighing no more than a pound. In the region of the sacral vertebrae of the brontosaurus, there was an expansion of the spinal cord. Being much larger than the brain, it controlled the musculature of the hind limbs and tail.

Ornithischian dinosaurs are divided into bipedal and quadrupedal. different in size and appearance, they fed mainly on vegetation, but predators also appear among them.

Stegosaurs are herbivores. Stegosaurus is especially abundant in North America, from where several species of these animals are known, reaching a length of 6 m. The back was steeply convex, the height of the animal reached 2.5 m. The body was massive, although the stegosaurus moved on four legs, its forelimbs were much shorter rear. On the back, large bone plates rose in two rows, protecting the spinal column. At the end of the short, thick tail, used by the animal for defense, there were two pairs of sharp spikes. Stegosaurus was a vegetarian and had an exceptionally small head and, accordingly, a tiny brain, a little more walnut. Interestingly, the expansion of the spinal cord in the sacral region, associated with the innervation of powerful hind limbs, was much larger in diameter than the brain.
Many scaly lepidosaurs appear - small predators with beak-shaped jaws.

In the Jurassic period, flying lizards first appear. They flew with the help of a leathery shell stretched between the long finger of the hand and the bones of the forearm. Flying lizards were well adapted to flight. They had light tubular bones. The extremely elongated outer fifth finger of the forelimbs consisted of four joints. The first finger looked like a small bone or was completely absent. The second, third and fourth fingers consisted of two, rarely three bones and had claws. The hind limbs were quite strongly developed. They had sharp claws at their ends. The skull of flying lizards was relatively large, as a rule, elongated and pointed. In old lizards, the cranial bones fused and the skulls became similar to the skulls of birds. The premaxilla sometimes grew into an elongated toothless beak. Toothed lizards had simple teeth and sat in recesses. The largest teeth were in front. Sometimes they stick out to the side. This helped the lizards to catch and hold prey. The spine of animals consisted of 8 cervical, 10-15 dorsal, 4-10 sacral and 10-40 caudal vertebrae. Rib cage was wide and had a high keel. The shoulder blades were long, the pelvic bones were fused. The most characteristic representatives of flying lizards are pterodactyl and rhamphorhynchus.

Pterodactyls in most cases were tailless, different in size - from the size of a sparrow to a crow. They had wide wings and a narrow skull extended 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 in rocks. The skin of pterodactyls was wrinkled and bare. They ate mainly fish, sometimes sea lilies, mollusks, and insects. In order to take off, pterodactyls had to jump off rocks or trees.
Rhamphorhynchus had long tails, long narrow wings, a large skull with numerous teeth. Long teeth of various sizes arched forward. The lizard's tail ended in a blade that served as a rudder. Ramphorhynchus could take off from the ground. They settled on the banks of rivers, lakes and seas, fed on insects and fish.

Flying lizards lived only in mesozoic era, and their heyday falls on the late Jurassic period. Their ancestors were apparently extinct ancient reptiles pseudosuchia. The long-tailed forms appeared before the short-tailed ones. At the end of the Jurassic, they became extinct.
It should be noted that flying lizards were not the ancestors of birds and bats. Flying lizards, birds and the bats originated and developed each in its own way, and there are no close family ties between them. The only thing they have in common is the ability to fly. And although they all acquired this ability due to a change in the forelimbs, the differences in the structure of their wings convince us that they had completely different ancestors.

The seas of the Jurassic period were inhabited by dolphin-like reptiles - ichthyosaurs. They had a long head sharp teeth, big eyes surrounded by a bony ring. The length of the skull of some of them was 3 m, and the body length was 12 m. The limbs of ichthyosaurs consisted of bone plates. Elbow, metatarsus, hand and fingers did not differ much in shape from each other. About a hundred bone plates supported a wide flipper. Shoulder and pelvic girdle were poorly developed. There were several fins on the body. Ichthyosaurs were viviparous animals.

Along with ichthyosaurs lived plesiosaurs. Appeared in the Middle Triassic, they reached their peak already in the Lower Jurassic, in the Cretaceous they were common in all seas. They were divided into two main groups: long-necked with a small head (plesiosaurs proper) and short-necked with a fairly massive head (pliosaurs). The limbs turned into powerful flippers, which became the main organ of swimming. The more primitive Jurassic pliosaurs originate mainly from Europe. Plesiosaurus from the Lower Jura, reached a length of 3 m. These animals often came ashore to rest. Plesiosaurs were not as dexterous in water as pliosaurs. To a certain extent, this shortcoming was compensated by the development of a long and very flexible neck, with the help of which plesiosaurs could seize prey with lightning speed. They ate mainly fish and shellfish.
In the Jurassic period, new genera of fossil turtles appear, and at the end of the period, modern turtles.
Tailless frog-like amphibians lived in fresh water.

There were a lot of fish in the Jurassic seas: bony, rays, sharks, cartilaginous, ganoid. They had an internal skeleton made of flexible cartilaginous tissue impregnated with calcium salts: a dense bony scaly cover that protected them well from enemies, and jaws with strong teeth.
Of the invertebrates in the Jurassic seas, ammonites, belemnites, sea lilies were found. However, in the Jurassic period, there were much fewer ammonites than in the Triassic. The Jurassic ammonites also differ from the Triassic in their structure, with the exception of the phyloceras, which did not change at all during the transition from the Triassic to the Jura. Separate groups of ammonites have preserved mother-of-pearl to our time. Some animals lived in the open sea, others inhabited bays and shallow inland seas.

Cephalopods - belemnites - swam in whole flocks in the Jurassic seas. Along with small specimens, there were real giants - up to 3 m long.
The remains of internal shells of belemnites, known as "devil's fingers", are found in the sediments of the Jurassic period.
In the seas of the Jurassic period, bivalve mollusks, especially those belonging to the oyster family, also developed significantly. They start to form oyster jars. Significant changes are taking place sea ​​urchins settled on reefs. Along with the round forms that have survived to this day, there lived bilaterally symmetrical, irregularly shaped hedgehogs. Their body was stretched in one direction. Some of them had a jaw apparatus.

The Jurassic seas were relatively shallow. The rivers brought muddy water into them, delaying gas exchange. Deep bays were filled with decaying remains and silt containing a large amount of hydrogen sulfide. That is why in such places the remains of animals, carried by sea currents or waves, are well preserved.
Many crustaceans appear: barnacles, decapods, leaf-legged crayfish, freshwater sponges, among insects - dragonflies, beetles, cicadas, bedbugs.

Deposits of coal, gypsum, oil, salt, nickel and cobalt are associated with the Jurassic deposits.



For the first time, deposits of this period were found in the Jura (mountains in Switzerland and France), hence the name of the period. The Jurassic period is subdivided into three divisions: leyas, doger and malm.

The deposits of the Jurassic period are quite diverse: limestones, clastic rocks, shales, igneous rocks, clays, sands, conglomerates formed in a variety of conditions.

Sedimentary rocks containing many representatives of fauna and flora are widely distributed.

Intensive tectonic movements at the end of the Triassic and at the beginning of the Jurassic contributed to the deepening of the large bays that gradually separated Africa and Australia from Gondwana. The gulf between Africa and America deepened. Depressions formed in Eurasia: German, Anglo-Paris, West Siberian. The Arctic Sea flooded the northern coast of Laurasia.

Intense volcanism and mountain-building processes led to the formation of the Verkhoyansk fold system. The formation of the Andes and the Cordillera continued. Warm sea currents have reached the Arctic latitudes. The climate became warm and humid. This is evidenced by the significant distribution of coral limestones and the remains of thermophilic fauna and flora. There are very few deposits of a dry climate: lagoonal gypsum, anhydrites, salts and red sandstones. The cold season already existed, but it was characterized only by a decrease in temperature. There was no snow or ice.

The climate of the Jurassic period depended on more than just sunlight. Numerous volcanoes and outpourings of magma on the bottom of the oceans heated up the water and the atmosphere, saturating the air with the steam of water, which then fell as rain on land, flowing in stormy streams into lakes and oceans. Numerous freshwater deposits testify to this: white sandstones alternating with dark loams.

The warm and humid climate favored the flourishing of the plant world. Ferns, cicadas, and conifers formed extensive marshy forests. Araucaria, arborvitae, cicadas grew on the coast. Ferns and horsetails formed the undergrowth. In the Lower Jurassic, the vegetation throughout the northern hemisphere was fairly uniform. But already starting from the Middle Jurassic, two plant belts can be identified: the northern one, in which ginkgo and herbaceous ferns predominated, and the southern one, with bennetites, cicadas, araucaria, and tree ferns.

The characteristic ferns of the mountain period were matonii, which have survived to this day in the Malay

archipelago. Horsetails and club mosses almost did not differ from modern ones. The place of extinct seed ferns and cordaites is occupied by cycads, which still grow in tropical forests.

Ginkgoaceae were also widely distributed. Their leaves turned to the sun with an edge and resembled huge fans. From North America and New Zealand to Asia and Europe grew dense forests coniferous plants - araucaria and bennetites. The first cypress and, possibly, spruce trees appear.

The representatives of the Jurassic conifers also include sequoia - a modern giant California pine. Currently, sequoias remain only on the Pacific coast of North America. Separate forms have been preserved. even more ancient plants, such as glassopteris. But there are few such plants, since they were supplanted by more perfect ones.

The lush vegetation of the Jurassic period contributed to the widespread distribution of reptiles. Dinosaurs have greatly evolved. Among them are lizard and ornithischian. Lizards moved on four legs, had five toes on their feet, and ate plants. Most of them had a long neck, a small head and a long tail. They had two brains: one small, in the head; the second is much larger in size - at the base of the tail.

The largest of the Jurassic dinosaurs was the brachiosaurus, reaching a length of 26 m, weighing about 50 tons. It had columnar legs, a small head, and a thick long neck. Brachiosaurs lived on the shores of the Jurassic lakes, fed on aquatic vegetation. Every day, the brachiosaurus needed at least half a ton of green mass.

Diplodocus is the oldest reptile, its length was 28 m. It had a long thin neck and a long thick tail. Like a brachiosaurus, diplodocus moved on four legs, the hind legs were longer than the front ones. Diplodocus spent most of its life in swamps and lakes, where it grazed and escaped from predators.

Brontosaurus was comparatively tall, had a large hump on its back and a thick tail. Its length was 18 m. The vertebrae of the brontosaurus were hollow. Chisel-shaped small teeth were densely located on the jaws of a small head. The brontosaurus lived in swamps, on the shores of lakes.

, conglomerates formed in a variety of conditions.

Jurassic subdivision

The Jurassic system is subdivided 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
	Medium (dogger)	Callovian	166,1-163,5
		Bath	168,3-166,1
		Bayosian	170,3-168,3
		Aalen	174,1-170,3
	Lower (lias)	Toarian	182,7-174,1
		Plinsbachsky	190,8-182,7
		Sinemursky	199,3-190,8
		Goettansky	201,3-199,3
Triassic	Upper	Rhetic	more
The division is given in accordance with 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).

Vegetation

In the Jurassic, vast areas were covered with lush vegetation, primarily a variety of forests. They mainly consisted of ferns and gymnosperms.

land animals

One of the fossil creatures that combine the features of birds and reptiles is Archeopteryx, or the first bird. For the first time, his skeleton was discovered in the so-called lithographic slates in Germany. The find was made two years after the publication of Charles Darwin's work " 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 that was not directly related to real birds) . Archeopteryx flew rather poorly (planned from tree to tree), and was about 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, they were preserved only in hoatzin chicks).

In the Jurassic period, small, woolly warm-blooded animals live on Earth - mammals. They live next to dinosaurs and are almost invisible against their background. In the Jurassic, the division of mammals into monotremes, marsupials, and placentals took place.

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Notes

Literature

• Jordan N. N. development of life on earth. - M .: Enlightenment, 1981.
• Karakash N.I.,. Jurassic system and period // Brockhaus and Efron Encyclopedic Dictionary: 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 .: Thought, 1984.
• Yasamanov N.A. Ancient climates of the Earth. - L.: Gidrometeoizdat, 1985.
• Yasamanov N.A. Popular paleogeography. - M .: Thought, 1985.

Links

• - A site about the Jurassic period, a big library paleontological books and articles.

←	P a l e about h about th	Mesozoic (252.2-66.0 Ma)			To a th n about h about th	→
←		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 naked and featureless, lazily moving their drooping, thorny branches. Farther behind them stretched a bleak, burnt-out steppe, lost in the distance behind a wall of dirty, gray fog... True, it did not cause the slightest pleasure to make one want to look at it ... The whole landscape evoked horror and longing, seasoned with hopelessness ...
- Oh, how scary it is here ... - Stella whispered, shivering. – 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. After all, no one sent them here - they just got what they deserved, right? Still not giving up, I said.
“Now look…” Stella whispered mysteriously.
Before us suddenly appeared a cave overgrown with grayish greenery. And out of it, squinting, stepped out a tall, stately man who in no way fit into this miserable, chilling landscape ...
- Hello, Sad! Stella greeted the stranger affectionately. - I brought a friend! She does not 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, - Yes, I'm not so good to show me to someone. You are right...
Oddly enough, but this sad man I really liked something right away. He exuded strength and warmth, and it was very pleasant to be near him. In any case, he did not in any way resemble those weak-willed, heartbroken people who surrendered to the mercy of fate with whom this “floor” was packed.
“Tell us your story, sad person…” Stella asked with a light smile.
“Yes, there is nothing to tell there, and there is nothing special to be proud of ...” the stranger shook his head. - And what do you need it for?
For some reason, I felt very sorry for him... Even without knowing anything about him, I was already almost sure that this person could not have done something really bad. Well, I just couldn’t!.. Stella, smiling, followed my thoughts, which she apparently liked very much ...
- Well, okay, I agree - you're right! .. - Seeing her satisfied face, I finally honestly admitted.
“But you don’t know anything about him yet, and everything is not so simple with him,” Stella said with a sly smile. “Well, please tell her, Sad…”
The man smiled sadly at us, and quietly said:
- I'm here because I killed ... I killed many. But not by desire, but by need, it was ...
I was immediately terribly upset - I killed! .. And I, stupid, believed! .. But for some reason I stubbornly did not have the slightest feeling of rejection or hostility. I obviously liked the person, and no matter how hard I tried, I couldn’t do anything about it ...
“Is it the same fault to kill at will or out of necessity?” I asked. Sometimes people don't have a choice, do they? For example: when they have to defend themselves or protect others. I have always admired heroes – warriors, knights. In general, I have 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’m here says that the guilt is the same... But from the way I feel this guilt in my heart, then no... I never wanted to kill, I just I defended my land, I was a hero there... But here it turned out that I was just killing... Is that right? I think no...
So you were a warrior? I asked hopefully. - But then, it's a big difference - you defended your home, your family, your children! And you don't look like a killer!
– Well, we are all different from what others see us... Because they only see what they want to see... or only what we want to show them... As for the war, I also first just as you thought, 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 happened.
– But this is not right! .. – I was indignant. - What then happens - a maniac-killer turns out to be the same as a hero?! .. This simply cannot be, this should not be!
Everything in 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 life in the same way. Only, probably, there are “extenuating circumstances”, since a person who protects someone, even if he takes his life, is 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, you believe me ...
- And can I ask you - how long have you lived? I asked, a little embarrassed.
– Oh, quite a long time ago... This is the second time I've been here... For some reason, my two lives were similar - in both I fought for someone... Well, and then I paid... And it's always just as bitter ... - the stranger was silent for a long time, as if not wanting to talk about it anymore, but then he continued quietly. There are people who love to fight. I've always hated it. But for some reason, life brings me back 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 captured foreign lands - others the lands were protected. Sons overthrew their fathers, brothers killed their brothers... Everything happened. Someone accomplished unthinkable feats, someone betrayed someone, and someone turned out to be just a coward. But none of them even suspected how bitter the payment for everything they did in that life would be ...
- Did you have a family there? to change the subject, I asked. - Were there children?
- Of course! But that was already so long ago!.. They once became great-grandfathers, then died... And some are already living again. That was a long time ago...
– And you are still here?!.. – I whispered, looking around in horror.
I could not even imagine that he had existed here like this for many, many years, suffering and "paying" his guilt, without any hope of leaving this terrifying "floor" even before his hour of return to the physical came. Earth! .. And there he will again have to start all over again, so that after, when his next “physical” life ends, he will return (perhaps right here!) With a whole new “baggage”, good or bad, depending on how he will live his "next" earthly life... And to free himself from this vicious circle (whether it be good or bad) he could not have any hope, since, having begun his earthly life, each person "dooms" himself to this endless, eternal circular "journey"... And, depending on his actions, returning to the "floors" can be very pleasant, or very scary ...