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Mesozoic era plant and animal. Jurassic period Mesozoic era

Mesozoic era

The Mesozoic era is an era of middle life. It is named so because the flora and fauna of this era are transitional between the Paleozoic and Cenozoic. During the Mesozoic era, the modern outlines of continents and oceans, modern marine fauna and flora gradually formed. The Andes and Cordillera, the mountain ranges of China and East Asia, were formed. The depressions of the Atlantic and Indian oceans were formed. The formation of the Pacific Ocean depressions began.

The Mesozoic era is divided into three periods: Triassic, Jurassic and Cretaceous.

Triassic

The Triassic period got its name from the fact that its deposits include three different complexes of rocks: the lower - continental sandstone, the middle - limestone and the upper - Naper.

The most characteristic deposits of the Triassic period are: continental sandy-clayey rocks (often with lenses of coal); marine limestones, clays, shales; lagoonal anhydrites, salts, gypsum.

During the Triassic period, the northern continent of Laurasia united with the southern one - Gondwana. A large bay that began in the east of Gondwana extended all the way to the northern coast of modern Africa, then turned south, almost completely separating Africa from Gondwana. A long bay stretched from the west, separating the western part of Gondwana from Laurasia. Many depressions appeared on Gondwana, which were gradually filled with continental sediments.

During the Middle Triassic, volcanic activity intensified. Inland seas become shallow and numerous depressions form. The formation of the mountain ranges of Southern China and Indonesia begins. In the territory of the modern Mediterranean, the climate was warm and humid. It was cooler and wetter in the Pacific zone. Deserts dominated the territory of Gondwana and Laurasia. The climate of the northern half of Laurasia was cold and dry.

Along with changes in the distribution of sea and land, the formation of new mountain ranges and volcanic areas, there was an intensive replacement of some animal and plant forms by others. Only a few families moved from the Paleozoic era to the Mesozoic. This gave grounds for some researchers to claim about the great catastrophes that occurred at the boundary of the Paleozoic and Mesozoic. However, when studying the deposits of the Triassic period, one can easily verify that there is no sharp line between them and the Permian deposits; therefore, some forms of plants and animals were replaced by others, probably gradually. The main reason was not catastrophes, but the evolutionary process: more perfect forms gradually replaced less perfect ones.

The seasonal temperature changes of the Triassic period began to have a noticeable effect on plants and animals. Certain groups of reptiles have adapted to cold seasons. It was from these groups that mammals originated in the Triassic, and somewhat later, birds. At the end of the Mesozoic era, the climate became even colder. Deciduous woody plants appear, which partially or completely shed their leaves during cold seasons. This feature of plants is an adaptation to a colder climate.

The cooling during the Triassic period was insignificant. It manifested itself most strongly in northern latitudes. The rest of the area was warm. Therefore, reptiles felt quite well in the Triassic period. Their most diverse forms, with which small mammals were not yet able to compete, settled across the entire surface of the Earth. The rich vegetation of the Triassic period also contributed to the extraordinary flourishing of reptiles.

Gigantic forms of cephalopods developed in the seas. The diameter of the shells of some of them was up to 5 m. True, even now the seas are inhabited by gigantic cephalopods, for example squids, reaching 18 m in length, but in the Mesozoic era there were much more gigantic forms.

The composition of the atmosphere of the Triassic period changed little compared to the Permian. The climate became wetter, but deserts remained in the center of the continent. Some plants and animals of the Triassic period have survived to this day in the region of Central Africa and South Asia. This suggests that the composition of the atmosphere and the climate of individual land areas remained almost unchanged during the Mesozoic and Cenozoic eras.

And yet stegocephalians became extinct. They were replaced by reptiles. More perfect, mobile, well adapted to a variety of living conditions, they ate the same food as stegocephals, settled in the same places, ate the young of stegocephals and ultimately exterminated them.

Among the Triassic flora, calamites, seed ferns and cordaites were also occasionally found. True ferns, ginkgo ferns, bennetite ferns, cycads, and conifers predominated. Cycads still exist in the Malay Archipelago region. They are known as sago palms. In appearance, cycads occupy an intermediate place between palm trees and ferns. The cycad trunk is quite thick and columnar. The crown consists of hard, feathery leaves arranged in a corolla. Plants reproduce using macro- and microspores.

Triassic ferns were coastal herbaceous plants that had wide, dissected leaves with reticulated venation. Volttsia has been well studied among coniferous plants. It had a thick crown and cones like those of a spruce.

Ginkgo trees were quite tall trees, their leaves formed dense crowns.

A special place among the Triassic gymnosperms was occupied by bennettites - trees with whorled large compound leaves, reminiscent of the leaves of cycads. The reproductive organs of bennetites occupy an intermediate place between the cones of cycads and the flowers of some flowering plants, in particular magnolias. Thus, it is probably the bennetites that should be considered the ancestors of flowering plants.

Of the invertebrates of the Triassic period, all types of animals that exist in our time are already known. The most characteristic marine invertebrates were reef-building animals and ammonites.

In the Paleozoic, animals already existed that covered the bottom of the sea in colonies, forming reefs, although not very powerful. During the Triassic period, when many colonial six-rayed corals appear instead of tabulates, the formation of reefs up to a thousand meters thick begins. The cups of six-rayed corals had six or twelve calcareous partitions. As a result of the massive development and rapid growth of corals, underwater forests were formed on the seabed, in which numerous representatives of other groups of organisms settled. Some of them took part in reef formation. Bivalves, algae, sea urchins, starfish, and sponges lived between the corals. Destroyed by waves, they formed coarse-grained or fine-grained sand, which filled all the voids of the corals. Washed out of these voids by waves, calcareous silt was deposited in bays and lagoons.

Some bivalves are quite characteristic of the Triassic period. Their paper-thin shells with fragile ribs form in some cases entire layers in the sediments of a given period. Bivalves lived in shallow muddy bays - lagoons, on reefs and between them. In the Upper Triassic period, many thick-shelled bivalves appeared, firmly attached to the limestone deposits of shallow basins.

At the end of the Triassic, due to increased volcanic activity, part of the limestone deposits was covered with ash and lavas. The steam rising from the bowels of the Earth brought with it many compounds from which deposits of non-ferrous metals were formed.

The most common of the gastropods were prosobranchs. Ammonites spread widely in the seas of the Triassic period, the shells of which accumulated in huge quantities in some places. Having appeared in the Silurian period, they did not yet play a major role among other invertebrates throughout the Paleozoic era. Ammonites could not successfully compete with the rather complex nautiloids. Ammonite shells were formed from calcareous plates that were the thickness of tissue paper and therefore did little to protect the soft body of the mollusk. Only when their partitions bent into numerous folds did the shells of ammonites acquire strength and turn into real shelter from predators. With the increasing complexity of the partitions, the shells became even more durable, and the external structure gave them the opportunity to adapt to a wide variety of living conditions.

Representatives of echinoderms were sea urchins, lilies and stars. At the upper end of the body of crinoids there was a flower-like main part. It distinguishes between a corolla and grasping organs - “hands”. Between the “hands” in the corolla there were the oral and anal openings. With its “hands” the sea lily scooped water into its mouth, and with it the sea animals that it fed on. The stem of many Triassic crinoids was spiral.

The Triassic seas were inhabited by calcareous sponges, bryozoans, leaf-footed crayfish, and ostracods.

Fish were represented by sharks that lived in fresh water bodies and molluscoids that inhabited the sea. The first primitive bony fishes appear. Powerful fins, well-developed dental apparatus, perfect shape, strong and light skeleton - all this contributed to the rapid spread of bony fish in the seas of our planet.

Amphibians were represented by stegocephalians from the labyrinthodont group. These were sedentary animals with a small body, small limbs and a large head. They lay in the water waiting for prey, and when the prey approached, they grabbed it. Their teeth had complex labyrinthine folded enamel, which is why they were called labyrinthodonts. The skin was moistened by mucous glands. Other amphibians came onto land to hunt insects. The most characteristic representatives of labyrinthodonts are mastodonosaurs. These animals, whose skulls reached one meter in length, resembled huge frogs in appearance. They hunted fish and therefore rarely left the aquatic environment.

Mastodonosaurus.

The swamps became smaller, and mastodonosaurs were forced to populate deeper and deeper places, often accumulating in large numbers. That is why many of their skeletons are now found in small areas.

Reptiles in the Triassic are characterized by significant diversity. New groups are appearing. Of the cotylosaurs, only procolophons remain - small animals that fed on insects. An extremely interesting group of reptiles was represented by archosaurs, which included thecodonts, crocodiles and dinosaurs. Representatives of thecodonts, ranging in size from a few centimeters to 6 m, were predators. They also differed in a number of primitive features and were similar to the Permian pelycosaurs. Some of them - pseudosuchia - had long limbs, a long tail and led a terrestrial lifestyle. Others, including the crocodyliform phytosaurs, lived in the water.

Crocodiles of the Triassic period - small primitive protosuchian animals - lived in fresh water bodies.

Among the dinosaurs, theropods and prosauropods appear. Theropods moved on well-developed hind limbs, had a heavy tail, powerful jaws, and small and weak forelimbs. The size of these animals ranged from a few centimeters to 15 m. All of them were classified as predators.

Prosauropods typically ate plants. Some of them were omnivores. They walked on four legs. Prosauropods had a small head, long neck and tail.

Representatives of the subclass of synaptosaurs led a very diverse lifestyle. Trilophosaurus climbed trees and ate plant foods. In appearance he resembled a cat.

Seal-like reptiles lived near the coast, feeding mainly on mollusks. Plesiosaurs lived in the sea, but sometimes came ashore. They reached 15 m in length. They ate fish.

In some places, quite often they find footprints of a huge animal that walked on four legs. It was called chirotherium. Based on the preserved prints, one can imagine the structure of the foot of this animal. Four gangly toes surrounded a thick, fleshy sole. Three of them had claws. The forelimbs of Chirotherium are almost three times smaller than the hind limbs. The animal left deep footprints on the wet sand. As new layers were deposited, the traces gradually petrified. Later, the land was flooded by the sea, hiding the traces. They turned out to be covered with marine sediments. Consequently, the sea flooded repeatedly during that era. The islands sank below sea level, and the animals living on them were forced to adapt to new conditions. Many reptiles appear in the sea, which undoubtedly descended from continental ancestors. Turtles with a wide bony shell, dolphin-like ichthyosaurs - fish lizards and gigantic plesiosaurs with a small head on a long neck - quickly developed. Their vertebrae are transformed, their limbs change. The cervical vertebrae of an ichthyosaur grow together into one bone, and in turtles they grow to form the upper part of the shell.

The ichthyosaur had a row of uniform teeth; in turtles the teeth disappear. The five-fingered limbs of ichthyosaurs turn into flippers well adapted for swimming, in which it is difficult to distinguish the shoulder, forearm, wrist and finger bones.

Starting from the Triassic period, reptiles, which moved to live in the sea, gradually populated increasingly vast areas of the ocean.

The oldest mammal found in the Triassic sediments of North Carolina is called dromaterium, which means “running beast.” This “beast” was only 12 cm in length. Dromatherium belonged to oviparous mammals. They, like the modern Australian echidna and platypus, did not give birth to young, but laid eggs, from which underdeveloped young hatched. Unlike reptiles, which did not care at all about their offspring, Dromatheriums fed their young with milk.

Deposits of oil, natural gases, brown and hard coal, iron and copper ores, and rock salt are associated with deposits of the Triassic period.

The Triassic period lasted 35 million years.

Jurassic period

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 divided 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 wide variety of conditions.

Sedimentary rocks containing many representatives of fauna and flora are widespread.

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

Intense volcanism and mountain-building processes determined the formation of the Verkhoyansk fold system. The formation of the Andes and Cordillera continued. Warm sea currents reached 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. Very few deposits of dry climates are found: 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 not only on sunlight. Many volcanoes and magma outpourings onto the bottom of the oceans heated the water and atmosphere, saturating the air with water vapor, which then rained onto the land and flowed into lakes and oceans in stormy streams. This is evidenced by numerous freshwater deposits: white sandstones alternating with dark loams.

The warm and humid climate favored the flourishing of the plant world. Ferns, cycads, and conifers formed vast swampy forests. Araucarias, thujas, and cycads grew on the coast. Ferns and horsetails formed the undergrowth. In the Lower Jurassic, throughout the northern hemisphere, vegetation was quite monotonous. But starting from the Middle Jurassic, two plant zones can be identified: the northern, in which ginkgo and herbaceous ferns predominated, and the southern with bennetites, cycads, araucarias, and tree ferns.

The characteristic ferns of the Jurassic period were matonia, which are still preserved in the Malay Archipelago. Horsetails and mosses were almost no different from modern ones. The place of extinct seed ferns and cordaites is taken by cycads, which still grow in tropical forests.

Ginkgo plants were also widespread. Their leaves turned edge-on to the sun and resembled huge fans. From North America and New Zealand to Asia and Europe, dense forests of coniferous plants - araucarias and bennetites - grew. The first cypress and possibly spruce trees appear.

Representatives of the Jurassic conifers also include sequoia - the modern giant California pine. Currently, redwoods remain only on the Pacific coast of North America. Some forms of even more ancient plants, for example glassopteris, have been preserved. But there are few such plants, since they were replaced by more advanced ones.

The lush vegetation of the Jurassic period contributed to the widespread distribution of reptiles. Dinosaurs have evolved significantly. Among them, lizard-hatched and ornithischian are distinguished. Lizards moved on four legs, had five toes on their feet, and ate plants. Most of them had a long neck, small head and long tail. They had two brains: one small one 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 and weighing about 50 tons. It had columnar legs, a small head, and a thick long neck. Brachiosaurs lived on the shores of Jurassic lakes and fed on aquatic vegetation. Every day, the brachiosaurus needed at least half a ton of green mass.

Brachiosaurus.

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 walked on four legs, the hind legs being longer than the front ones. Diplodocus spent most of its life in swamps and lakes, where it grazed and escaped from predators.

Diplodocus.

Brontosaurus was relatively 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 the small head. The brontosaurus lived in swamps and on the shores of lakes.

Brontosaurus.

Ornithischian dinosaurs are divided into bipeds and quadrupeds. Different in size and appearance, they fed mainly on vegetation, but predators are already appearing among them.

Stegosaurs are herbivores. They had two rows of large plates on their backs and paired spikes on their tails that protected them from predators. Many scaly lepidosaurs appear - small predators with beak-like jaws.

Flying lizards first appeared in the Jurassic period. They flew using 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 tube-shaped bones. The extremely elongated outer fifth digit 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 developed. There were sharp claws at their ends. The skull of flying lizards was relatively large, usually elongated and pointed. In old lizards, the cranial bones fused and the skulls became similar to the skulls of birds. The premaxillary bone sometimes grew into an elongated toothless beak. Toothed lizards had simple teeth and sat in recesses. The largest teeth were in the front. Sometimes they stuck out to the side. This helped the lizards catch and hold prey. The animals' spine consisted of 8 cervical, 10–15 dorsal, 4–10 sacral and 10–40 caudal vertebrae. The chest was wide and had a high keel. The shoulder blades were long, the pelvic bones were fused. The most typical representatives of flying lizards are pterodactyl and rhamphorhynchus.

Pterodactyl.

Pterodactyls in most cases were 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, sometimes sea lilies, mollusks, and insects. In order to fly, pterodactyls were forced to jump from cliffs or trees.

Rhamphorhynchus had long tails, long narrow wings, and a large skull with numerous teeth. Long teeth of varying sizes curved forward. The lizard's tail ended in a blade that served as a rudder. Rhamphorhynchus could take off from the ground. They settled on the banks of rivers, lakes and seas, feeding on insects and fish.

Rhamphorhynchus.

Flying lizards lived only in the Mesozoic era, and their heyday occurred in the Late Jurassic period. Their ancestors were, apparently, extinct ancient reptiles pseudosuchians. Long-tailed forms appeared earlier than short-tailed ones. At the end of the Jurassic period they became extinct.

It should be noted that flying lizards were not the ancestors of birds and bats. Flying lizards, birds and bats each originated and developed in their 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 changes 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, large eyes surrounded by a bony ring. The length of the skull of some of them was 3 m, and the length of the body was 12 m. The limbs of ichthyosaurs consisted of bone plates. The elbow, metatarsus, hand and fingers differed little from each other in shape. About a hundred bone plates supported the wide flipper. The shoulder and pelvic girdles were poorly developed. There were several fins on the body. Ichthyosaurs were viviparous animals. Plesiosaurs lived alongside ichthyosaurs. They had a thick body with four flipper-like limbs, a long snake-like neck with a small head.

During the Jurassic period, new genera of fossil turtles appeared, and at the end of the period, modern turtles appeared.

Tailless frog-like amphibians lived in fresh water bodies. There were a lot of fish in the Jurassic seas: bony fish, stingrays, sharks, cartilaginous fish, and ganoid fish. They had an internal skeleton made of flexible cartilaginous tissue impregnated with calcium salts: a dense bony scaly covering that protected them well from enemies, and jaws with strong teeth.

Among the invertebrates in the Jurassic seas, there were ammonites, belemnites, and crinoids. However, in the Jurassic period there were much fewer ammonites than in the Triassic. Jurassic ammonites differ from Triassic ammonites in their structure, with the exception of phyloceras, which did not change at all during the transition from the Triassic to the Jurassic. Certain groups of ammonites have preserved mother-of-pearl to this day. Some animals lived in the open sea, others inhabited bays and shallow inland seas.

Cephalopods - belemnites - swam in whole schools in the Jurassic seas. Along with small specimens, there were real giants - up to 3 m long.

Remains of belemnite internal shells, known as “devil's fingers,” are found in Jurassic sediments.

In the seas of the Jurassic period, bivalves also developed significantly, especially those belonging to the oyster family. They begin to form oyster banks.

The sea urchins that settled on the reefs are undergoing significant changes. 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. Rivers brought muddy water into them, delaying gas exchange. The deep bays were filled with rotting debris and silt containing large amounts of hydrogen sulfide. That is why in such places the remains of animals carried by sea currents or waves are well preserved.

Sponges, starfish, and crinoids often overflow the Jurassic sediments. “Five-armed” crinoids became widespread during the Jurassic period. Many crustaceans appear: barnacles, decapods, phyllopods, freshwater sponges, among insects - dragonflies, beetles, cicadas, bugs.

The first birds appeared during the Jurassic period. Their ancestors were the ancient reptiles pseudosuchians, which also gave rise to dinosaurs and crocodiles. Ornithosuchia is most similar to birds. She, like a bird, walked on her hind legs, had a strong pelvis and was covered with feather-like scales. Some pseudosuchians moved to live in trees. Their forelimbs were specialized for grasping branches with their fingers. The pseudosuchian skull had lateral depressions, which significantly reduced the mass of the head. Climbing trees and jumping on branches strengthened the hind limbs. Gradually expanding forelimbs supported the animals in the air and allowed them to glide. An example of such a reptile is Scleromochlusa. His long, thin legs indicate that he was a good jumper. Elongated forearms helped animals climb and cling to branches of trees and bushes. The most important moment in the process of transformation of reptiles into birds was the transformation of scales into feathers. The animals' hearts had four chambers, which ensured a constant body temperature.

In the Late Jurassic period, the first birds appeared - Archeopteryx, the size of a pigeon. In addition to short feathers, Archeopteryx had seventeen flight feathers on its wings. The tail feathers were located on all tail vertebrae and were directed back and down. Some researchers believe that the bird's feathers were bright, like those of modern tropical birds, others that the feathers were gray or brown, and still others that they were motley. The mass of the bird reached 200 g. Many signs of Archeopteryx indicate its family ties with reptiles: three free fingers on the wings, a head covered with scales, strong conical teeth, a tail consisting of 20 vertebrae. The bird's vertebrae were biconcave, like those of fish. Archeopteryx lived in araucaria and cycad forests. They ate mainly insects and seeds.

Archeopteryx.

Predators appeared among mammals. Small in size, they lived in forests and dense bushes, hunting small lizards and other mammals. Some of them have adapted to life in trees.

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

This period lasted 55 million years.

Cretaceous period

The Cretaceous period received this name because thick chalk deposits are associated with it. It is divided into two sections: lower and upper.

Mountain-building processes at the end of the Jurassic period significantly changed the outlines of continents and oceans. North America, previously separated from the vast Asian continent by a wide strait, connected with Europe. In the east, Asia merged with America. South America was completely separated from Africa. Australia was located where it is today, but was smaller in size. The formation of the Andes and Cordilleras, as well as individual ridges of the Far East, continues.

During the Upper Cretaceous period, the sea flooded vast areas of the northern continents. Western Siberia and Eastern Europe, most of Canada and Arabia were under water. Thick layers of chalk, sand, and marls accumulate.

At the end of the Cretaceous period, mountain-building processes were again activated, as a result of which the mountain ranges of Siberia, the Andes, the Cordillera and the mountain ranges of Mongolia were formed.

The climate has changed. In the high latitudes in the north, during the Cretaceous period there was already a real winter with snow. Within the boundaries of the modern temperate zone, some tree species (walnut, ash, beech) were no different from modern ones. The leaves of these trees fell for the winter. However, as before, the climate in general was much warmer than today. Ferns, cycads, ginkgos, bennetites, and conifers, in particular sequoias, yews, pines, cypresses, and spruces, were still common.

In the mid-Cretaceous period, flowering plants flourished. At the same time, they displace representatives of the most ancient flora - spore and gymnosperm plants. It is believed that flowering plants originated and developed in the northern regions, and subsequently they spread throughout the planet. Flowering plants are much younger than conifers, known to us since the Carboniferous period. The dense forests of giant tree ferns and horsetails had no flowers. They adapted well to the living conditions of that time. However, gradually the humid air of the primary forests became increasingly dry. There was very little rain, and the sun was unbearably hot. The soil in the areas of primary swamps dried out. Deserts appeared on the southern continents. Plants moved to areas with cooler, wetter climates in the north. And then the rains came again, saturating the damp soil. The climate of ancient Europe became tropical, and forests similar to modern jungles arose on its territory. The sea recedes again, and plants that inhabited the coast in a humid climate found themselves in a drier climate. Many of them died, but some adapted to new living conditions, forming fruits that protected the seeds from drying out. The descendants of such plants gradually populated the entire planet.

The soil also underwent changes. Silt and the remains of plants and animals enriched it with nutrients.

In primary forests, plant pollen was carried only by wind and water. However, the first plants appeared, the pollen of which insects fed on. Some of the pollen stuck to the wings and legs of the insects, and they transferred it from flower to flower, pollinating the plants. In pollinated plants, the seeds ripened. Plants that were not visited by insects did not reproduce. Therefore, only plants with fragrant flowers of various shapes and colors were distributed.

With the advent of flowers, insects also changed. Among them appear insects that cannot live without flowers at all: butterflies, bees. Fruits with seeds developed from pollinated flowers. Birds and mammals ate these fruits and carried the seeds over long distances, spreading the plants to new areas of the continents. Many herbaceous plants appeared and populated the steppes and meadows. The leaves of the trees fell off in the fall and curled up in the summer heat.

The plants spread to Greenland and the islands of the Arctic Ocean, where it was relatively warm. At the end of the Cretaceous period, with the cooling of the climate, many cold-resistant plants appeared: willow, poplar, birch, oak, viburnum, which are also characteristic of the flora of our time.

With the development of flowering plants, by the end of the Cretaceous period the bennetites became extinct, and the number of cycads, ginkgos, and ferns decreased significantly. Along with the change in vegetation, the fauna also changed.

Foraminifera spread significantly, the shells of which formed thick chalk deposits. The first nummulites appear. Corals formed reefs.

Ammonites of the Cretaceous seas had shells of a peculiar shape. If all the ammonites that existed before the Cretaceous period had shells wrapped in one plane, then the Cretaceous ammonites had elongated shells, bent in the form of a knee, and there were spherical and straight shells. The surface of the shells was covered with spines.

According to some researchers, the bizarre forms of Cretaceous ammonites are a sign of aging of the entire group. Although some representatives of ammonites still continued to reproduce at high speed, their vital energy almost dried up during the Cretaceous period.

According to other scientists, ammonites were exterminated by numerous fish, crustaceans, reptiles, and mammals, and the strange forms of Cretaceous ammonites are not a sign of aging, but mean an attempt to somehow protect themselves from excellent swimmers, which by that time had become bony fish and sharks.

The disappearance of ammonites was also facilitated by a sharp change in physical and geographical conditions in the Cretaceous period.

Belemnites, which appeared much later than ammonites, also completely died out during the Cretaceous period. Among the bivalves there were animals of different shapes and sizes that closed the valves with the help of denticles and pits. In oysters and other mollusks that attach to the seabed, the valves become different. The lower flap looked like a deep bowl, and the upper one looked like a lid. Among the rudists, the lower valve turned into a large thick-walled glass, inside of which only a small chamber remained for the mollusk itself. The round, lid-like upper flap covered the lower one with strong teeth, with the help of which it could rise and fall. Rudists lived mainly in the southern seas.

In addition to bivalves, whose shells consisted of three layers (outer horny, prismatic and mother-of-pearl), there were mollusks with shells that had only a prismatic layer. These are mollusks of the genus Inoceramus, widely distributed in the seas of the Cretaceous period - animals that reached one meter in diameter.

During the Cretaceous period, many new species of gastropods appeared. Among sea urchins, the number of irregular heart-shaped forms especially increases. And among sea lilies, varieties appear that do not have a stem and float freely in the water with the help of long feathery “arms”.

Great changes have also occurred among fish. In the seas of the Cretaceous period, ganoid fish gradually became extinct. The number of bony fishes is increasing (many of them still exist today). Sharks are gradually acquiring a modern appearance.

Numerous reptiles still lived in the sea. The descendants of the ichthyosaurs that became extinct at the beginning of the Cretaceous period reached 20 m in length and had two pairs of short flippers.

New forms of plesiosaurs and pliosaurs appear. They lived on the open sea. Crocodiles and turtles inhabited freshwater and saltwater basins. The territory of modern Europe was inhabited by large lizards with long spines on their backs and huge pythons.

Of the terrestrial reptiles, trachodons and horned lizards were especially characteristic of the Cretaceous period. Trachodons could move on both two and four legs. They had membranes between their fingers that helped them swim. Trachodons' jaws resembled a duck's beak. They had up to two thousand small teeth.

Triceratops had three horns on their heads and a huge bone shield that reliably protected the animals from predators. They lived mainly in dry places. They ate vegetation.

Triceratops.

Styracosaurs had nasal projections - horns and six horny spines on the posterior edge of the bony shield. Their heads reached two meters in length. The spines and horns made Styracosaurus dangerous to many predators.

The most terrible predatory lizard was the Tyrannosaurus. It reached a length of 14 m. Its skull, more than a meter long, had large sharp teeth. The tyrannosaurus moved on powerful hind legs, supported by a thick tail. Its front legs were small and weak. The tyrannosaurs left fossilized footprints 80 cm long. The tyrannosaurus's step was 4 m.

Tyrannosaur.

Ceratosaurus was a relatively small but fast predator. It had a small horn on its head and a bone crest on its back. The ceratosaurus walked on its hind legs, each of which had three toes with large claws.

Torbosaurus was rather clumsy and hunted mainly on sedentary scolosaurs, which resembled modern armadillos in appearance. Thanks to their powerful jaws and strong teeth, torbosaurs easily chewed through the thick bony shell of scolosaurs.

Scolosaurus.

Flying lizards still continued to exist. The huge pteranodon, whose wingspan was 10 m, had a large skull with a long bony crest on the back of its head and a long toothless beak. The animal's body was relatively small. Pteranodons ate fish. Like modern albatrosses, they spent most of their lives in the air. Their colonies were located by the sea. Recently, the remains of another pteranodon were found in the Cretaceous sediments of America. Its wingspan reached 18 m.

Pteranodon.

Birds appeared that could fly well. Archeopteryx became completely extinct. However, some birds had teeth.

In Hesperornis, a waterfowl, the long finger of the hind limbs was connected to three others by a short swimming membrane. All the fingers had claws. All that remained of the forelimbs were slightly bent humerus bones in the form of a thin stick. Hesperornis had 96 teeth. Young teeth grew inside the old ones and replaced them as soon as they fell out. Hesperornis is very similar to the modern loon. It was very difficult for him to move on land. Raising the front part of the body and pushing off the ground with its feet, Hesperornis moved in small jumps. However, he felt free in the water. He dived well, and it was very difficult for fish to avoid his sharp teeth.

Hesperornis.

Ichthyornis, contemporaries of Hesperornis, was the size of a dove. They flew well. Their wings were highly developed, and the chest bone had a high keel, to which powerful pectoral muscles were attached. The beak of Ichthyornis had many small teeth curved back. The small brain of Ichthyornis resembled the brain of reptiles.

Ichthyornis.

In the Late Cretaceous period, toothless birds appeared, whose relatives - flamingos - still exist today.

Amphibians are no longer different from modern ones. And mammals are represented by carnivores and herbivores, marsupials and placentals. They do not yet play a significant role in nature. However, at the end of the Cretaceous period - the beginning of the Cenozoic era, when giant reptiles became extinct, mammals spread widely across the Earth, taking the place of dinosaurs.

There are many hypotheses regarding the reasons for the extinction of dinosaurs. Some researchers believe that the main reason for this was mammals, of which many appeared at the end of the Cretaceous period. Predatory mammals exterminated dinosaurs, and herbivores intercepted plant food from them. A large group of mammals ate dinosaur eggs. According to other researchers, the main reason for the mass death of dinosaurs was a sharp change in physical and geographical conditions at the end of the Cretaceous period. Cold temperatures and droughts led to a sharp decrease in the number of plants on Earth, as a result of which the giant dinosaurs began to feel a lack of food. They were dying. And the predators for whom dinosaurs served as prey also died, since they had nothing to eat. Perhaps the sun's heat was not enough for the embryos to mature in dinosaur eggs. In addition, cold temperatures also had a detrimental effect on adult dinosaurs. Not having a constant body temperature, they depended on the temperature of the environment. Like modern lizards and snakes, they were active in warm weather, but moved sluggishly in cold weather, could fall into winter torpor and became easy prey for predators. Dinosaurs' skin did not protect them from the cold. And they hardly cared about their offspring. Their parental functions were limited to laying eggs. Unlike dinosaurs, mammals had a constant body temperature, and therefore suffered less from cold snaps. In addition, they were protected by wool. And most importantly, they fed their cubs with milk and took care of them. Thus, mammals had certain advantages over dinosaurs.

Birds that had a constant body temperature and were covered with feathers also survived. They incubated eggs and fed chicks.

Among the reptiles that survived were those that took refuge from the cold in burrows and lived in warm areas. From them came modern lizards, snakes, turtles and crocodiles.

The deposits of the Cretaceous period are associated with large deposits of chalk, coal, oil and gas, marls, sandstones, and bauxites.

The Cretaceous period lasted 70 million years.

From the book Journey to the Past author Golosnitsky Lev Petrovich

Mesozoic era - the Middle Ages of the earth Life takes over land and air What changes and improves living beings? The collections of fossils collected in the geological and mineralogical museum have already told us a lot: about the depths of the Cambrian sea, where people similar to

From the book Before and After Dinosaurs author Zhuravlev Andrey Yurievich

Mesozoic restructuring Compared to the Paleozoic “immobility” of bottom animals in the Mesozoic, everything literally spread out and spread out in all directions (fish, cuttlefish, snails, crabs, sea urchins). The sea lilies waved their arms and came off the bottom. Scallop bivalves

From the book How life arose and developed on Earth author Gremyatsky Mikhail Antonovich

XII. Mesozoic (“middle”) era The Paleozoic era ended with a whole revolution in the history of the Earth: a huge glaciation and the death of many animal and plant forms. In the Middle Era we no longer find very many of those organisms that existed hundreds of millions

The origin of life on Earth occurred about 3.8 billion years ago, when the formation of the earth's crust ended. Scientists have found that the first living organisms appeared in an aquatic environment, and only after a billion years did the first creatures emerge on the surface of the land.

The formation of terrestrial flora was facilitated by the formation of organs and tissues in plants and the ability to reproduce by spores. Animals also evolved significantly and adapted to life on land: internal fertilization, the ability to lay eggs, and pulmonary respiration appeared. An important stage in development was the formation of the brain, conditioned and unconditioned reflexes, and survival instincts. The further evolution of animals provided the basis for the formation of humanity.

Dividing the history of the Earth into eras and periods gives an idea of the features of the development of life on the planet in different time periods. Scientists identify particularly significant events in the formation of life on Earth in separate periods of time - eras, which are divided into periods.

There are five eras:

Archean;
Proterozoic;
Paleozoic;
Mesozoic;
Cenozoic.

The Archean era began about 4.6 billion years ago, when planet Earth was just beginning to form and there were no signs of life on it. The air contained chlorine, ammonia, hydrogen, the temperature reached 80°, the level of radiation exceeded permissible limits, under such conditions the origin of life was impossible.

It is believed that about 4 billion years ago our planet collided with a celestial body, and the consequence was the formation of the Earth’s satellite, the Moon. This event became significant in the development of life, stabilized the planet’s rotation axis, and contributed to the purification of water structures. As a result, the first life arose in the depths of the oceans and seas: protozoa, bacteria and cyanobacteria.

The Proterozoic era lasted from approximately 2.5 billion years ago to 540 million years ago. Remains of unicellular algae, mollusks, and annelids were discovered. Soil begins to form.

The air at the beginning of the era was not yet saturated with oxygen, but in the process of life, bacteria inhabiting the seas began to increasingly release O 2 into the atmosphere. When the amount of oxygen was at a stable level, many creatures took a step in evolution and switched to aerobic respiration.

The Paleozoic era includes six periods.

Cambrian period(530 - 490 million years ago) is characterized by the emergence of representatives of all species of plants and animals. The oceans were inhabited by algae, arthropods, and mollusks, and the first chordates (haikouihthys) appeared. The land remained uninhabited. The temperature remained high.

Ordovician period(490 – 442 million years ago). The first settlements of lichens appeared on land, and megalograptus (a representative of arthropods) began to come ashore to lay eggs. In the depths of the ocean, vertebrates, corals, and sponges continue to develop.

Silurian(442 – 418 million years ago). Plants come to land, and the rudiments of lung tissue form in arthropods. The formation of the bone skeleton in vertebrates is completed, and sensory organs appear. Mountain building is underway and different climatic zones are being formed.

Devonian(418 – 353 million years ago). The formation of the first forests, mainly ferns, is characteristic. Bone and cartilaginous organisms appear in reservoirs, amphibians began to come to land, and new organisms—insects—are formed.

Carboniferous period(353 – 290 million years ago). The appearance of amphibians, the subsidence of the continents, at the end of the period there was a significant cooling, which led to the extinction of many species.

Permian period(290 – 248 million years ago). The earth is inhabited by reptiles; therapsids, the ancestors of mammals, appeared. The hot climate led to the formation of deserts, where only hardy ferns and some conifers could survive.

The Mesozoic era is divided into 3 periods:

Triassic(248 – 200 million years ago). Development of gymnosperms, appearance of the first mammals. The split of land into continents.

Jurassic period(200 - 140 million years ago). The emergence of angiosperms. The appearance of the ancestors of birds.

Cretaceous period(140 – 65 million years ago). Angiosperms (flowering plants) became the dominant group of plants. Development of higher mammals, true birds.

The Cenozoic era consists of three periods:

Lower Tertiary period or Paleogene(65 – 24 million years ago). The disappearance of most cephalopods, lemurs and primates appear, later parapithecus and dryopithecus. The development of the ancestors of modern mammal species - rhinoceroses, pigs, rabbits, etc.

Upper Tertiary period or Neogene(24 – 2.6 million years ago). Mammals inhabit land, water, and air. The appearance of Australopithecines - the first ancestors of humans. During this period, the Alps, Himalayas, and Andes were formed.

Quaternary or Anthropocene(2.6 million years ago – today). A significant event of the period was the appearance of man, first the Neanderthals, and soon Homo sapiens. The flora and fauna acquired modern features.

The Mesozoic era began approximately 250 and ended 65 million years ago. It lasted 185 million years. The Mesozoic is known primarily as the era of dinosaurs. These giant reptiles overshadow all other groups of living beings. But you shouldn’t forget about others. After all, it was the Mesozoic - the time when real mammals, birds, and flowering plants appeared - that actually formed the modern biosphere. And if in the first period of the Mesozoic - the Triassic, there were still many animals on Earth from Paleozoic groups that were able to survive the Permian catastrophe, then in the last period - the Cretaceous, almost all those families that flourished in the Cenozoic era had already formed.

In the Mesozoic, not only dinosaurs arose, but also other groups of reptiles, which are often mistakenly considered dinosaurs - aquatic reptiles (ichthyosaurs and plesiosaurs), flying reptiles (pterosaurs), lepidosaurs - lizards, among which were aquatic forms - mosasaurs. Snakes evolved from lizards - they also appeared in the Mesozoic - the time of their emergence is generally known, but paleontologists argue about the environment in which this occurred - in water or on land.

Sharks flourished in the seas, and they also lived in freshwater bodies. The Mesozoic is the era of the flourishing of two groups of cephalopods - ammonites and belemnites. But in their shadow, the nautiluses, which arose in the early Paleozoic and still exist, lived well, and the familiar squids and octopuses arose.

In the Mesozoic, modern mammals arose, first marsupials and then placentals. In the Cretaceous period, groups of ungulates, insectivores, predators and primates had already emerged.

Interestingly, modern amphibians - frogs, toads and salamanders - also arose in the Mesozoic, presumably in the Jurassic period. So, despite the antiquity of amphibians in general, modern amphibians are a relatively young group.

Throughout the Mesozoic, vertebrates sought to master a new environment for themselves - the air. The first reptiles were able to take off - first small pterosaurs - rhamphorhynchus, then larger pterodactyls. Somewhere on the border of the Jurassic and Cretaceous, reptiles took to the air - small feathered dinosaurs, capable, if not of flight, then certainly of gliding, and the descendants of reptiles - birds - enantiornis and true fan-tailed birds.

A real revolution in the biosphere occurred with the advent of angiosperms - flowering plants. This resulted in an increase in the diversity of insects that became flower pollinators. The gradual spread of flowering plants has changed the appearance of terrestrial ecosystems.

The Mesozoic ended with the famous mass extinction, better known as the “extinction of the dinosaurs.” The reasons for this extinction are not clear, but the more we learn about the events that took place at the end of the Cretaceous, the less convincing the popular hypothesis of a meteorite catastrophe becomes. The Earth's biosphere was changing and the ecosystems of the Late Cretaceous were very different from the ecosystems of the Jurassic period. A huge number of species became extinct throughout the Cretaceous period, and not at all at its end - they simply did not survive the catastrophe. At the same time, evidence is emerging that in some places the typical Mesozoic fauna still existed at the very beginning of the next era - the Cenozoic. So for now, it is not possible to unequivocally answer the question about the causes of the extinction that occurred at the end of the Mesozoic. It is only clear that if some kind of catastrophe did occur, it only pushed the changes that had already begun

My acquaintance with the Eganovsky quarry began in 2009, when it was not yet such a popular place. At that wonderful time, ammonites could be collected without the help of a shovel directly from the surface of the dumps, and the question of the availability of the bedrock layer with ammonites of the genus Virgatites was not as pressing as in the current 2011. In this article I would like to discuss ammonites of the genus Virgatites in general and the Late Ivanovi in particular. Many are confused by the preservation of the Eganovsky Virgatites and, comparing them with the Lopatinsky ones, ... >>>

Moscow region, North, expansion of the Small Concrete Ring under construction. Intelligence service. PART 1 On May 11, 2018, I was lucky enough to ride on a small concrete road from Krasnoarmeysk to Dmitrovka. This is the north. There, in recent years, the construction of a new roadway and a bypass section bypassing Iksha has been underway. And finally, I had the opportunity to stop in a couple of places and explore the overburden created by the construction. So, at the first point, which is opposite the Aleshino tuberculosis dispensary, I stopped purely by chance, having seen... >>>

Eona. The Mesozoic consists of three periods - Cretaceous, Jurassic and Triassic. The Mesozoic era lasted for 186 million years, starting 251 million years ago and ending 66 million years ago. To avoid getting confused about eons, eras and periods, use the geochronological scale, which is located, as a visual clue.

The lower and upper boundaries of the Mesozoic are defined by two mass extinctions. The lower limit is marked by the largest extinction in the history of the Earth - the Permian or Permian-Triassic, when about 90-96% of marine animals and 70% of terrestrial animals disappeared. The upper limit is marked by perhaps the most famous extinction event - the Cretaceous-Paleogene, when all the dinosaurs became extinct.

Periods of the Mesozoic era

1. or Triassic period. Lasted from 251 to 201 million years ago. The Triassic is known for the fact that during this period the mass extinction ends and the gradual restoration of the Earth's fauna begins. Also in the Triassic period, the largest supercontinent in history, Pangea, begins to break apart.

2. or Jurassic period. Lasted from 201 to 145 million years ago. Active development of plants, marine and terrestrial animals, giant dinosaurs and mammals.

3. or Cretaceous period. Lasted from 145 to 66 million years ago. The beginning of the Cretaceous period is characterized by the further development of flora and fauna. Large reptile dinosaurs reigned on the earth, some of which reached 20 meters in length and eight meters in height. The mass of some dinosaurs reached fifty tons. The first birds appeared in the Cretaceous period. At the end of the period, the Cretaceous disaster occurred. As a result of this disaster, many species of plants and animals disappeared. The biggest losses were among the dinosaurs. At the end of the period, ALL dinosaurs became extinct, as well as many gymnosperms, many aquatic reptiles, pterosaurs, ammonites, as well as 30 to 50% of all animal species that were able to survive.

Animals of the Mesozoic era

Apatosaurus

Archeopteryx

Askeptosaurus

Brachiosaurus

Diplodocus

Sauropods

Ichthyosaurs

Camarasaurus

Liopleurodon

Mastodonsaurus

Mosasaurs

Nothosaurs

Plesiosaurs

Sclerosaurus

Tarbosaurus

Tyrannosaurus

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The Mesozoic is an era of tectonic, climatic and evolutionary activity. The formation of the main contours of modern continents and mountain building on the periphery of the Pacific, Atlantic and Indian oceans is taking place; the division of land facilitated speciation and other important evolutionary events. The climate was warm throughout the entire time period, which also played an important role in the evolution and formation of new animal species. By the end of the era, the bulk of the species diversity of life approached its modern state.

Geological periods

Triassic period (252.2 ± 0.5 - 201.3 ± 0.2)
Jurassic (201.3 ± 0.2 - 145.0 ± 0.8)
Cretaceous period (145.0 ± 0.8 - 66.0).

The lower (between the Permian and Triassic periods, that is, between the Paleozoic and Mesozoic) boundary is marked by the Permo-Triassic mass extinction, which resulted in the death of approximately 90-96% of marine fauna and 70% of land vertebrates. The upper limit is set at the Cretaceous-Paleogene boundary, when another very large extinction of many groups of plants and animals occurred, most often attributed to the impact of a giant asteroid (Chicxulub crater on the Yucatan Peninsula) and the subsequent “asteroid winter”. Approximately 50% of all species became extinct, including all flightless dinosaurs.

Tectonics and paleogeography

Compared to the vigorous mountain building of the late Paleozoic, Mesozoic tectonic deformation can be considered relatively mild. The era was characterized primarily by the division of the supercontinent Pangea into a northern continent, Laurasia, and a southern continent, Gondwana. This process led to the formation of the Atlantic Ocean and passive continental margins, in particular much of the modern Atlantic coast (for example, the eastern coast of North America). Extensive transgressions that prevailed in the Mesozoic led to the emergence of numerous inland seas.

By the end of the Mesozoic, the continents had practically taken on their modern shape. Laurasia was divided into Eurasia and North America, Gondwana into South America, Africa, Australia, Antarctica and the Indian subcontinent, the collision of which with the Asian continental plate caused intense orogenesis with the uplift of the Himalayan mountains.

Africa

At the beginning of the Mesozoic era, Africa was still part of the supercontinent Pangea and had a relatively common fauna with it, which was dominated by theropods, prosauropods and primitive ornithischian dinosaurs (by the end of the Triassic).

Late Triassic fossils are found throughout Africa, but are more common in the south than in the north of the continent. As is known, the time line separating the Triassic from the Jurassic period is marked by a global catastrophe with mass extinction of species (Triassic-Jurassic extinction), but the African layers of this time remain poorly studied today.

Early Jurassic fossil deposits are distributed similarly to Late Triassic deposits, with more frequent exposures in the south of the continent and fewer deposits towards the north. Throughout the Jurassic period, iconic dinosaur groups such as sauropods and ornithopods increasingly spread across Africa. The paleontological layers of the mid-Jurassic period in Africa are poorly represented and also poorly studied.

Late Jurassic strata are also poorly represented here, with the exception of the impressive Tendeguru Jurassic assemblage in Tanzania, whose fossils are very similar to those found in the paleobiotic Morrison Formation of western North America and date to the same period.

In the mid-Mesozoic, about 150-160 million years ago, Madagascar separated from Africa, while remaining connected to India and the rest of Gondwanaland. Abelisaurs and titanosaurs have been discovered among the fossils of Madagascar.

During the Early Cretaceous era, a part of the landmass that made up India and Madagascar separated from Gondwana. In the Late Cretaceous, the divergence of India and Madagascar began, which continued until the achievement of modern outlines.

Unlike Madagascar, mainland Africa was tectonically relatively stable throughout the Mesozoic. And yet, despite its stability, significant changes occurred in its position relative to other continents as Pangea continued to break apart. By the beginning of the Late Cretaceous period, South America separated from Africa, thereby completing the formation of the Atlantic Ocean in its southern part. This event had a huge impact on the global climate by changing ocean currents.

During the Cretaceous, Africa was inhabited by allosauroids and spinosaurids. The African theropod Spinosaurus turned out to be one of the largest carnivores that lived on Earth. Among herbivores in the ancient ecosystems of those times, titanosaurs occupied an important place.

Cretaceous fossil deposits are more common than Jurassic deposits, but often cannot be radiometrically dated, making it difficult to determine their exact age. Paleontologist Louis Jacobs, who has spent considerable time in field work in Malawi, argues that African fossil deposits "need more careful excavation" and are sure to prove "fruitful ... for scientific discoveries."

Climate

Over the past 1.1 billion years, Earth's history has seen three successive ice age-warming cycles, called Wilson cycles. Longer warm periods were characterized by a uniform climate, a greater diversity of flora and fauna, and a predominance of carbonate sediments and evaporites. Cold periods with glaciations at the poles were accompanied by a decrease in biodiversity, terrigenous and glacial sediments. The reason for cyclicity is considered to be the periodic process of connecting continents into a single continent (Pangea) and its subsequent disintegration.

The Mesozoic era is the warmest period in the Phanerozoic history of the Earth. It almost completely coincided with the period of global warming, which began in the Triassic period and ended in the Cenozoic era with the Little Ice Age, which continues to this day. For 180 million years, even in the subpolar regions there was no stable ice cover. The climate was mostly warm and even, without significant temperature gradients, although climatic zonation existed in the northern hemisphere. The large amount of greenhouse gases in the atmosphere contributed to the uniform distribution of heat. The equatorial regions were characterized by a tropical climate (Tethys-Panthalassa region) with an average annual temperature of 25–30°C. Up to 45-50° N The subtropical region (Peritethys) extended, followed by the warm-temperate boreal zone, and the subpolar regions were characterized by a cool-temperate climate.

During the Mesozoic there was a warm climate, mostly dry in the first half of the era and humid in the second. Slight cooling in the late Jurassic and the first half of the Cretaceous, strong warming in the middle of the Cretaceous (the so-called Cretaceous temperature maximum), around the same time the equatorial climate zone appeared.

Flora and fauna

Giant ferns, tree horsetails, and mosses are dying out. In the Triassic, gymnosperms, especially conifers, flourished. In the Jurassic period, seed ferns died out and the first angiosperms appeared (so far represented only by woody forms), which gradually spread to all continents. This is due to a number of advantages; Angiosperms have a highly developed conducting system, which ensures reliable cross-pollination, the embryo is supplied with food reserves (due to double fertilization, a triploid endosperm develops) and is protected by membranes, etc.

In the animal world, insects and reptiles flourish. Reptiles occupy a dominant position and are represented by a large number of forms. In the Jurassic period, flying lizards appear and conquer the air. In the Cretaceous period, the specialization of reptiles continued, they reached enormous sizes. The mass of some of the dinosaurs reached 50 tons.

The parallel evolution of flowering plants and pollinating insects begins. At the end of the Cretaceous period, cooling sets in and the area of semi-aquatic vegetation decreases. Herbivores are dying out, followed by carnivorous dinosaurs. Large reptiles are preserved only in the tropical zone (crocodiles). Due to the extinction of many reptiles, a rapid adaptive radiation of birds and mammals begins, occupying the vacated ecological niches. Many forms of invertebrates and sea lizards are dying out in the seas.

Birds, according to most paleontologists, descended from one of the groups of dinosaurs. The complete separation of arterial and venous blood flows caused them to be warm-blooded. They spread widely over land and gave rise to many forms, including flightless giants.

The emergence of mammals is associated with a number of large aromorphoses that arose in one of the subclasses of reptiles. Aromorphoses: a highly developed nervous system, especially the cerebral cortex, which ensured adaptation to living conditions through changes in behavior, movement of the limbs from the sides under the body, the emergence of organs that ensure the development of the embryo in the mother’s body and subsequent feeding with milk, the appearance of fur, complete separation of the circulatory system, the appearance of alveolar lungs, which increase the intensity of gas exchange and, as a consequence, the overall level of metabolism.

Mammals appeared in the Triassic, but could not compete with dinosaurs and for 100 million years occupied a subordinate position in the ecological systems of that time.

Scheme of the evolution of flora and fauna in the Mesozoic era.

Literature

Iordansky N. N. Development of life on earth. - M.: Education, 1981.
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.