What animals lived in the Mesozoic era. Mesozoic period. Mesozoic era. History of the Earth. Characteristics of the Mesozoic era

The Mesozoic era is subdivided into the Triassic, Jurassic and Cretaceous periods.

After the intense mountain building of the Carboniferous and Permian periods, the Triassic period is characterized by relative tectonic calm. Only at the end of the Triassic, on the border with the Jura, does the ancient Cimmerian phase of the Mesozoic warehouse appear.

frequency. Volcanic processes in the Triassic are quite active, but their centers move to the Pacific geosynclinal belts and to the Mediterranean geosyncline. In addition, the formation of traps continues on the Siberian platform (Tunguska basin).

Both the Permian and the Triassic are characterized by a strong reduction in the area of ​​epicontinental seas. Vast expanses of present-day continents are almost devoid of Triassic marine sediments. The climate is continental. The animal world takes on the appearance that later became characteristic of the Mesozoic era as a whole. The sea is dominated by cephalopods (ammonites) and lamellar-gill mollusks; sea ​​lizards appear, already dominant on land. Gymnosperms (cycads, conifers and gingkoves) predominate among plants.

The Triassic deposits are poor in minerals (coal, building materials).

The Jurassic period is tectonically more intense. At the beginning of the Jurassic, the ancient Cimmerian, and at the end of the new Cimmerian phase of the Mesozoic (Pacific) folding appears. Within northern continents In the northern hemisphere, deep faults develop and troughs form in the northern hemisphere. In the southern hemisphere, the disintegration of the mainland Gondwana begins. Volcanism is actively manifested in geosynclinal belts.

Unlike the Triassic, the Jurassic is characterized by transgressions. Thanks to them, the climate becomes less continental. During this period, the further development of the flora of gymnosperms takes place.

Significant development of the fauna was expressed in a noticeable increase and specialization of species of marine and terrestrial animals. The development of lizards continues (predatory, herbivorous, marine, terrestrial, flying), the first species of birds and mammals appear. Dominate the sea cephalopods-ammonites, new species of sea urchins, lilies, etc.

The main minerals found in the Jurassic deposits are oil, gas, oil shale, coal, phosphorites, iron ores, bauxites and a number of others.

In the Cretaceous, intense mountain building takes place, called the Laramian phase of the Mesozoic folding. The Laramian orogeny developed with the greatest force at the boundary of the Lower and Upper Cretaceous, when extensive geosynclines arose in the Pacific geosynclines. mountainous countries. In the Mediterranean belt, this phase was preliminary and preceded the main orogeny, which developed later in the Cenozoic era.

For the southern hemisphere, in addition to mountain building in the Andes, the Cretaceous period was marked by further breaks in the Gondwana mainland, subsidence of large areas of land and the formation of depressions in the Indian Ocean and the South Atlantic Ocean. Faults in the earth's crust and mountain building were accompanied by the manifestation of volcanism.

Reptiles dominate the animal world of the Cretaceous period and many species of birds appear. There are few more mammals. Ammonites and lamella-gill molluscs continue to dominate the sea, sea ​​urchins, lilies, corals, and foraminifera are widely developed, from the shells of which (partially) the formation of strata of white writing chalk occurred. The flora of the Lower Cretaceous has a typical Mesozoic character. Gymnosperms continue to predominate in it, but in the Upper Cretaceous, the dominant role passes to angiosperms, close to modern ones.

On the platforms, Cretaceous deposits are distributed approximately in the same place as Jurassic ones and contain the same complex of minerals.

Considering mesozoic era in general, it should be noted that “it was marked by new manifestations of orogenic phases, which were most developed in the Pacific geosynclinal belts, for which the Mesozoic epoch of orogeny is often called the Pacific epoch. In the Mediterranean geosynclinal belt, this orogeny was preliminary. Attached as a result of the closure of geosynclines, young mountain structures increased the size of hard sections of the earth's crust. At the same time, mainly in the southern hemisphere, the opposite process began to develop - the disintegration of the ancient continental mass of Gondwana. Volcanic activity was no less intense in the Mesozoic than in the Paleozoic. Great changes have taken place in the composition of flora and fauna. Among terrestrial animals, reptiles flourished and declined at the end of the Cretaceous. Ammonites, belemnites and a number of other animals passed the same course of development in the seas. In the second half of the Cretaceous, an angiosperm flora appears in place of the gymnosperms that dominated the Mesozoic.

Of the minerals formed in the Mesozoic era, oil, gas, coal, phosphorites and various ores are of the greatest importance.

Aeon. The Mesozoic is made up of three periods Cretaceous, Jurassic and Triassic. The Mesozoic era lasted for 186 million years, starting from 251 million years ago and ending 66 million years ago. In order not to get confused in 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 land animals disappeared. The upper limit is marked by perhaps the most famous extinction - the Cretaceous-Paleogene, when all dinosaurs died out.

Periods of the Mesozoic Era

1. or Triassic. It 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 animal world of the Earth begins. Also in the Triassic period, Pangea, the largest supercontinent in history, begins to break apart.

2. or Jurassic. It lasted from 201 to 145 million years ago. Active development of plants, marine and land animals, giant lizard dinosaurs and mammals.

3. or Cretaceous period. It lasted from 145 to 66 million years ago. The beginning of the Cretaceous period is characterized further development flora and fauna. Large reptile dinosaurs reigned on 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 there was a Cretaceous catastrophe. As a result of this catastrophe, many species of plants and animals disappeared. The biggest losses were among the dinosaurs. At the end of the period, ALL dinosaurs died out, as well as many gymnosperms, many aquatic reptiles, pterosaurs, ammonites, as well as from 30 to 50% of the species of all animal species that could survive.

Animals of the Mesozoic Era

Apatosaurus

Archeopteryx

Askeptosaurus

Brachiosaurus

Diplodocus

sauropods

ichthyosaurs

Camarasaurus

Liopleurodon

Mastodonsaurus

Mosasaurs

Nothosaurs

Plesiosaurs

sclerosaurus

Tarbosaurus

tyrannosaurus rex

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Era. Continued for 56 million years. It began 201 million years ago and ended 145 million years ago. The geochronological scale of the history of the Earth of all eons, eras and periods is located.

The name "Jura" was named after the mountain range of the same name in Switzerland and France, where deposits of this period were first discovered. Later geological formations jurassic have been found in many other places on the planet.

In the Jurassic period, the Earth almost completely recovered from the largest in history. Various forms of life - marine organisms, land plants, insects and many animal species - begin to flourish and increase their species diversity. Dinosaurs reign in the Jurassic period - large, and sometimes just giant lizards. Dinosaurs existed almost everywhere and everywhere - in the seas, rivers and lakes, in swamps, forests, in open spaces. Dinosaurs got it big variety and the spread that over millions of years of evolution, some of them have become radically different from each other. Dinosaurs included both herbivores and carnivores. Some of them were the size of a dog, while others reached a height of more than ten meters.

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

Jurassic period animals

Allosaurus

Apatosaurus

Archeopteryx

Barosaurus

Brachiosaurus

Diplodocus

Dryosaurs

Giraffatitan

Camarasaurus

Camptosaurus

Kentrosaurus

Liopleurodon

Megalosaurus

Pterodactyls

ramphorhynchus

Stegosaurus

Scelidosaurus

Ceratosaurus

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Lesson topic:"The development of life in mesozoic era»

The duration of the Mesozoic era is approximately 160 million years. The Mesozoic era includes the Triassic (235-185 million years ago), Jurassic (185-135 million years) and Cretaceous (135-65 million years ago) periods. The development of organic life on Earth and the evolution of the biosphere continued against the background of paleogeographical changes characteristic of this stage.

The Triassic is characterized by a general uplift of platforms and an increase in land area.

By the end of the Triassic, the destruction of most mountain systems that emerged in the Paleozoic. The continents turned into huge plains, which in the next, Jurassic, period, the ocean began to advance. The climate became milder and warmer, capturing not only tropical and subtropical belt, but also modern temperate latitudes. During the Jurassic, the climate is warm and humid. The increased rainfall caused the formation of seas, huge lakes and large rivers. The change in physical and geographical conditions affected the development of the organic world. The extinction of representatives of the marine and terrestrial biota continued, which began in the arid Permian, which was called the Permian-Triassic crisis. After this crisis, and as a result of it, the flora and fauna of the land evolved.

In biological terms, the Mesozoic was a time of transition from old, primitive to new, progressive forms. The Mesozoic world was much more diverse than the Paleozoic, fauna and flora appeared in it in a significantly updated composition.

Flora

The vegetation cover of the land at the beginning of the Triassic period was dominated by ancient coniferous and seed ferns (pteridosperms). in arid climates, these gymnosperms gravitated to moist places. On the coasts of drying reservoirs and in disappearing swamps, the last representatives of ancient club mosses, some groups of ferns, perished. By the end of the Triassic, a flora was formed in which ferns, cycads, and ginkgoes dominated. Gymnosperms flourished during this period.

In the Cretaceous, flowering plants appeared and conquered the land.

The supposed ancestor of flowering plants, according to most scientists, was closely related to seed ferns and represented one of the branches of this group of plants. Paleontological remains of primary flowering plants and a group of plants intermediate between them and gymnosperm ancestors, unfortunately, are still unknown to science.

The primary type of flowering plant was, according to most botanists, an evergreen tree or low shrub. The herbaceous type of flowering plant appeared later under the influence of limiting environmental factors. The idea of ​​the secondary nature of the herbaceous type of angiosperms was first expressed in 1899 by the Russian botanical geographer A.N. Krasnov and the American anatomist C. Jeffrey.

The evolutionary transformation of woody forms into herbaceous ones occurred as a result of a weakening, and then a complete or almost complete decrease in the activity of the cambium. Such a transformation probably began at the dawn of the development of flowering plants. With the passage of time, it proceeded more rapidly in the most distant groups of flowering plants and eventually acquired such a wide scale that it covered all the main lines of their development.

Of great importance in the evolution of flowering plants was neoteny - the ability to reproduce at an early stage of ontogenesis. It is usually associated with limiting environmental factors - low temperature, lack of moisture and a short growing season.

Of the huge variety of woody and herbaceous forms, flowering plants turned out to be the only group of plants capable of forming complex multi-tiered communities. The emergence of these communities led to a more complete and intensive use of the natural environment, the successful conquest of new territories, especially unsuitable for gymnosperms.

In the evolution and mass dispersal of flowering plants, the role of pollinating animals is also great, especially insects. Feeding on pollen, insects carried it from one strobilus of the original angiosperm ancestors to another and, thus, were the first agents of cross-pollination. Over time, insects adapted to eat the ovules, already causing significant damage to plant reproduction. The reaction to such a negative influence of insects was the selection of adaptive forms with closed ovules.

The conquest of land by flowering plants marks one of the decisive, turning points in the evolution of animals. This parallelism between the suddenness and rapidity of the spread of angiosperms and mammals is explained by interdependent processes. The conditions associated with the flowering of angiosperms were also favorable for mammals.

Fauna

Fauna of the seas and oceans: Mesozoic invertebrates were already approaching modern ones in character. A prominent place among them was occupied by cephalopods, to which modern squids and octopuses belong. The Mesozoic representatives of this group included ammonites with a shell twisted into a "ram's horn", and belemnites, the inner shell of which was cigar-shaped and overgrown with the flesh of the body - the mantle. Ammonites were found in the Mesozoic in such quantities that their shells are found in almost all marine sediments of this time.

By the end of the Triassic, most of the ancient groups of ammonites die out, but in the Cretaceous period they are still numerous., but during the Late Cretaceous, the number of species in both groups begins to decline. The diameter of the shells of some ammonites reaches 2.5 m.

At the end of the Mesozoic, all ammonites became extinct. Of the cephalopods with an outer shell, only the genus Nautilus has survived to this day. Forms with an internal shell are more widely distributed in modern seas - octopuses, cuttlefish and squids, remotely related to belemnites.

Six-pointed corals began to actively develop(Hexacoralla), whose colonies were active reef-formers. Mesozoic echinoderms were represented by various types of crinoids, or crinoids (Crinoidea), which flourished in the shallow waters of the Jurassic and partly Cretaceous seas. However sea ​​urchins have made the most progress. Starfish were plentiful.

Bivalve molluscs also spread strongly.

During the Jurassic, the foraminifera flourished again that survived the Cretaceous period and reached modern times. In general, unicellular protozoa were an important component in the formation of Mesozoic sedimentary rocks. The Cretaceous period was also a time of rapid development of new types of sponges and some arthropods, in particular insects and decapods.

The Mesozoic era was a time of unstoppable expansion of vertebrates. Of the Paleozoic fish, only a few moved into the Mesozoic.. Among them were freshwater sharks, marine sharks continued to evolve throughout the Mesozoic; most modern genera were already represented in the seas of the Cretaceous, in particular.

Almost all the lobe-finned fish from which the first terrestrial vertebrates developed died out in the Mesozoic. Paleontologists believed that the crossopterans became extinct by the end of the Cretaceous. But in 1938 an event occurred that attracted the attention of all paleontologists. An individual of a fish species unknown to science was caught off the South African coast. Scientists who studied this unique fish came to the conclusion that it belongs to the "extinct" group of crossopterans ( Coelacanthida). Until now this view remains the only modern representative of the ancient lobe-finned fish. He got the name Latimeria chalumnae. Such biological phenomena are referred to as "living fossils".

Sushi fauna: New groups of insects appeared on land, the first dinosaurs and primitive mammals. The most widespread in the Mesozoic were reptiles, which became truly the dominant class of this era.

With the advent of dinosaurs early reptiles became completely extinct in the middle of the Triassic cotylosaurs and mammals, as well as the last large amphibian stegocephals. Dinosaurs, which were the most numerous and diverse superorder of reptiles, have become the leading Mesozoic group of terrestrial vertebrates since the end of the Triassic. For this reason, the Mesozoic is called the era of the dinosaurs. In the Jurassic, among the dinosaurs, real monsters could be found, up to 25-30 m long (with a tail) and weighing up to 50 tons. Of these giants, such forms as the brontosaurus (Brontosaurus), diplodocus (Diplodocus) and brachiosaurus (Brachiosaurus) are best known.

The original ancestors of the dinosaurs may have been the Upper Permian eosuchia, a primitive detachment of small reptiles with a physique resembling a lizard. From them, in all likelihood, a large branch of reptiles arose - archosaurs, which then broke up into three main branches - dinosaurs, crocodiles and winged pangolins. The archosaurs were thecodonts. Some of them lived in the water and outwardly resembled crocodiles. Others, like large lizards, lived in open areas of land. These terrestrial thecodonts adapted to bipedal walking, which provided them with the ability to observe in search of prey. It was from such thecodonts, which became extinct at the end of the Triassic, that dinosaurs originated, inheriting a bipedal mode of movement, although some of them switched to a quadrupedal mode of movement. Representatives of the climbing forms of these animals, which eventually switched from jumping to gliding flights, gave rise to pterosaurs (pterodactyls) and birds. Dinosaurs included both herbivores and carnivores.

By the end of the Cretaceous, the mass extinction of characteristic Mesozoic groups of reptiles, including dinosaurs, ichthyosaurs, plesiosaurs, pterosaurs and mosasaurs, occurs.

Members of the bird class (Aves) first appear in Jurassic deposits. The only known first bird was Archeopteryx. The remains of this first bird were found near the Bavarian city of Solnhofen (Germany). During the Cretaceous, bird evolution proceeded at a rapid pace; characteristic of this time, still possessing serrated jaws. The emergence of birds was accompanied by a number of aromorphoses: they acquired a hollow septum between the right and left ventricles of the heart, lost one of the aortic arches. The complete separation of arterial and venous blood flows determines the warm-bloodedness of birds. Everything else, namely, feather cover, wings, horny beak, air sacs and double breathing, as well as shortening of the hindgut, are idioadaptations.

First mammals (Mammalia), modest animals, not exceeding the size of a mouse, descended from animal-like reptiles in the late Triassic. Throughout the Mesozoic, they remained few in number, and by the end of the era, the original genera had largely died out. Their occurrence is associated with a number of major aromorphoses, developed in representatives of one of the subclasses of reptiles. These aromorphoses include: the formation of hairline and 4 chamber heart, complete separation of arterial and venous blood flow, intrauterine development of offspring and feeding the baby with milk. Aromorphoses include development of the cerebral cortex, causing the predominance of conditioned reflexes over unconditioned ones and the possibility of adapting to changing environmental conditions by changing behavior.

Almost all Mesozoic groups of the animal and plant kingdoms retreat, die out, disappear; arises on the ruins of the old new world, the world of the Cenozoic era, in which life receives a new impetus to development and, in the end, living species of organisms are formed.

Mesozoic era

Mesozoic era is the era average life. It is named so because the flora and fauna of this era are transitional between the Paleozoic and Cenozoic. In the Mesozoic era, the modern outlines of the continents and oceans, modern marine fauna and flora are gradually formed. The Andes and Cordilleras, mountain ranges of China and East Asia. The depressions of the Atlantic and Indian Oceans. 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 three different rock complexes are considered to be its deposits: the lower one is continental sandstone, the middle one is limestone and the upper one is neiper.

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

During the Triassic period, the northern continent of Laurasia merged with the southern continent - Gondwana. The great bay, which began in the east of Gondwana, extended all the way to the northern coast 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 arose on Gondwana, gradually filled with continental deposits.

Volcanic activity intensified in the Middle Triassic. The inland seas become shallow, and numerous depressions are formed. The formation of the mountain ranges of South China and Indonesia begins. On 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 regions, there was an intensive change of some animal and plant forms by others. Only a few families have moved from Paleozoic era to the Mesozoic. This gave grounds to some researchers to assert about the great catastrophes that occurred at the turn of the Paleozoic and Mesozoic. However, when studying the deposits of the Triassic period, one can easily see that there is no sharp boundary 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 change in temperatures of the Triassic period began to have a noticeable effect on plants and animals. Separate groups of reptiles have adapted to the 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 appear woody plants, which in the cold seasons partially or completely shed their leaves. This feature of plants is an adaptation to a colder climate.

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

Gigantic forms of cephalopods have developed in the seas. The diameter of the shells of some of them was up to 5 m. True, gigantic cephalopod mollusks, such as squid, reaching 18 m in length, still live in the seas, but in the Mesozoic era there were much more gigantic forms.

The composition of the atmosphere of the Triassic period has changed little compared to the Permian. The climate became more humid, but the deserts in the center of the continent remained. 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 have not changed much during the Mesozoic and Cenozoic eras.

And yet the stegocephalians died out. They were replaced by reptiles. More perfect, mobile, well adapted to various living conditions, they ate the same food as stegocephalians, settled in the same places, ate young stegocephalians and eventually exterminated them.

Among the Triassic flora, calamites, seed ferns, and cordaites were occasionally encountered. True ferns predominated, ginkgo, bennetite, cycad, coniferous. Cycads still exist in the area of ​​the Malay Archipelago. They are known as sago palms. In my own way appearance cycads occupy an intermediate position between palms and ferns. The trunk of cycads is rather thick, columnar. The crown consists of stiff pinnate leaves arranged in a corolla. Plants reproduce by means of macro- and microspores.

Triassic ferns were coastal herbaceous plants with broad, dissected leaves with reticulate venation. Of the coniferous plants, volttia has been well studied. She had a dense crown and cones like spruce.

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

A special place among the Triassic gymnosperms was occupied by bennetites - trees with whorled large complex leaves resembling 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 magnoliaceae. 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 typical 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. In the Triassic period, when many colonial six-pointed corals, the formation of reefs up to a thousand meters thick begins. Cups of six-pointed corals had six or twelve calcareous partitions. As a result of mass development and rapid growth corals at the bottom of the sea, underwater forests formed, in which numerous representatives of other groups of organisms settled. Some of them took part in reef formation. Bivalves, algae, sea urchins, starfish, sponges lived among the corals. Destroyed by waves, they formed coarse-grained or fine-grained sand, which filled all the voids of the corals. Washed out by waves from these voids, calcareous silt was deposited in bays and lagoons.

Some bivalve mollusks are quite characteristic of the Triassic period. Their paper-thin shells with brittle ribs in some cases form whole layers in the deposits of this period. Bivalves lived in shallow muddy bays - lagoons, on reefs and between them. In the Upper Triassic period, many thick-shell bivalve mollusks appeared, firmly attached to the limestone deposits of shallow water basins.

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

The most common of the gastropod molluscs were pronebranchial. Ammonites were widely distributed in the seas of the Triassic period, the shells of which in some places accumulated in huge numbers. Having appeared in the Silurian period, they did not yet play a large 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, which had the thickness of tissue paper and therefore almost did not protect the soft body of the mollusk. Only when their partitions were bent into numerous folds, ammonite shells gained strength and turned into a real shelter from predators. With the complication of the partitions, the shells became even more durable, and the external structure made it possible for them to adapt to the most diverse living conditions.

Representatives of echinoderms were sea urchins, lilies and stars. At the upper end of the body of sea lilies, there was a flower-like main body. It distinguishes a corolla and grasping organs - “hands”. Between the "hands" in the corolla were the mouth and anus. With “hands”, the sea lily raked water into the mouth opening, 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-legged crayfish, and ostracods.

The fish were represented by sharks living in freshwater bodies and molluscoids inhabiting the sea. The first primitive bony fish appear. Powerful fins, a well-developed dentition, a perfect shape, a 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 group of labyrinthodonts. They were sedentary animals with a small body, small limbs and a large head. They lay in the water waiting for the 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 with mucous glands. Other amphibians came out on land to hunt insects. Most characteristic representatives labyrinthodonts - 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 the mastodonosaurs were forced to populate more and more deep places, often accumulating in large numbers. That is why many of their skeletons are now being found in small areas.

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

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

Dinosaurs include theropods and prosauropods. Theropods moved on well-developed hind limbs, had a heavy tail, powerful jaws, small and weak forelimbs. In size, these animals ranged from a few centimeters to 15 m. All of them were predators.

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

Representatives of the synaptosaur subclass led the most diverse lifestyle. Trilophosaurus climbed trees, fed on plant foods. In appearance, he resembled a cat.

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

In some places, footprints of a huge animal walking on four legs are quite often found. They called it the chirotherium. Based on the surviving prints, one can imagine the structure of the foot of this animal. Four clumsy toes surrounded a thick, meaty sole. Three of them had claws. The forelimbs of the chirotherium are almost three times smaller than the hind ones. On the wet sand, the animal left deep footprints. With the deposition of new layers, the traces gradually petrified. Later, the land was flooded with the sea, which hid the traces. They were covered with marine sediments. Consequently, in that era, the sea repeatedly flooded. 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 mainland ancestors. Turtles with a wide bone shell, dolphin-like ichthyosaurs - fish-lizards and gigantic plesiosaurs with a small head on a long neck quickly developed. Their vertebrae are transformed, limbs are changed. The cervical vertebrae of an ichthyosaur fuse into one bone, and in turtles they grow, forming upper part shell.

The ichthyosaur had a row of homogeneous teeth; teeth disappear in turtles. 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.

Since the Triassic period, reptiles that have moved to live in the sea gradually populate more and more vast expanses of the ocean.

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

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

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 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 Laurasia: 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. Many volcanoes, outpourings of magma on the bottom of the oceans heated the water and the atmosphere, saturated the air with water vapor, which then rained 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: northern, dominated by ginkgo and herbaceous ferns, and southern with bennetites, cicadas, araucaria, tree ferns.

The characteristic ferns of the Jurassic 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 now 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, dense forests of coniferous plants grew - 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 of even more ancient plants have been preserved, for example, 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.

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 moved on four legs, the hind legs were longer than the front ones. Diplodocus spent most of his life in swamps and lakes, where he grazed and escaped from predators.

Diplodocus.

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.

Brontosaurus.

Ornithischian dinosaurs are divided into bipedal and quadrupedal. 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 beaked 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, usually 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 animal spine 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.

Pterodactyl.

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, molluscs, 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.

Ramphorhynchus.

Flying lizards lived only in the 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 one common feature for them - 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. They had a thick body with four flipper-like limbs, a long serpentine neck with a small head.

In the Jurassic, 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 cartilage tissue, impregnated with calcium salts: a dense bone 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 Jurassic deposits.

In the seas of the Jurassic, bivalve mollusks, especially those belonging to the oyster family, also developed significantly. They start to form oyster jars.

Significant changes are undergoing sea urchins that 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 in them muddy water delaying gas exchange. Deep bays were filled with decaying remains and silt containing large amounts of hydrogen sulfide. That is why in such places the remains of animals brought sea ​​currents or waves.

Sponges, starfish, sea lilies often overwhelm Jurassic deposits. In the Jurassic period, "five-armed" sea lilies became widespread. Many crustaceans appear: barnacles, decapods, leaf-legged crayfish, freshwater sponges, among insects - dragonflies, beetles, cicadas, bedbugs.

In the Jurassic period, the first birds appear. Their ancestors were the ancient reptile pseudosuchia, which also gave rise to dinosaurs and crocodiles. Ornithosuchia is most similar to birds. She, like birds, moved on her hind legs, had a strong pelvis and was covered with feather-like scales. Part of pseudosuchia moved to live on trees. Their forelimbs were specialized for grasping branches with their fingers. There were lateral depressions on the skull of Pseudosuchia, 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 scleromochlus. His long thin legs indicate that he jumped well. The elongated forearms helped the animals to climb and cling to the branches of trees and bushes. The most important moment in the process of turning reptiles into birds was the transformation of scales into feathers. The heart of the animals had four chambers, which ensured a constant body temperature.

In the late Jurassic period, the first birds appear - Archeopteryx, the size of a dove. 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 color, the third - that they were motley. The mass of the bird reached 200 g. Many signs of Archeopteryx speak of 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 vertebrae of the bird were biconcave, like those of fish. Archeopteryx lived in araucaria and cicada forests. They fed mainly on insects and seeds.

Archeopteryx.

Among mammals, predators appeared. 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 the Jurassic deposits.

This period lasted 55 million years.

Cretaceous period

The Cretaceous period got its name because powerful chalk deposits are associated with it. It is divided into two sections: lower and upper.

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

In the Upper Cretaceous period, the sea flooded vast areas of the northern continents. Under water were Western Siberia and Eastern Europe, most of Canada and Arabia. Thick strata of chalk, sands, and marls accumulate.

At the end of the Cretaceous, mountain building processes are 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 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 as a whole was much warmer than today. Ferns, cycads, ginkgos, bennetites, conifers, in particular sequoias, yews, pines, cypresses, and spruces were still common.

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

The soil has also changed. Silt, 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 fed on insects. Part of the pollen stuck to the wings and legs of insects, and they carried it from flower to flower, pollinating plants. In pollinated plants, the seeds ripened. Plants that were not visited by insects did not multiply. Therefore, only plants with fragrant flowers spread. various forms and colors.

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

Plants have spread across Greenland and the North Islands. Arctic Ocean where it was relatively warm. At the end of the Cretaceous, 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, the bennetites died out, and the number of cycads, ginkgos, and ferns significantly decreased. Along with the change in vegetation, the fauna also changed.

Foraminifers spread considerably, the shells of which formed thick deposits of chalk. 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, spherical and straight ones were encountered. The surface of the shells was covered with spikes.

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

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

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

Belemnites, which appeared much later than ammonites, also completely die out in the Cretaceous period. Among the bivalve mollusks there were animals, different in shape and size, closing the valves with the help of teeth and pits. In oysters and other mollusks attached to the seabed, the valves become different. The lower sash looked like a deep bowl, and the upper one looked like a lid. Among the Rudists, the lower wing turned into a large thick-walled glass, inside of which there was only a small chamber for the mollusk itself. The round, lid-like top flap covered the lower one with strong teeth, with which it could rise and fall. Rudists lived mainly in the southern seas.

In addition to bivalve mollusks, 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 settled in the seas of the Cretaceous period - animals that reached one meter in diameter.

In the Cretaceous period, many new species of gastropods appear. Among sea urchins, the number of irregular heart-shaped forms is especially increasing. 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 taken place among the fish. In the seas of the Cretaceous period, ganoid fish are gradually dying out. The number of bony fish is increasing (many of them still exist today). Sharks gradually acquire a modern look.

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

New forms of plesiosaurs and pliosaurs appear. They lived on the high seas. Crocodiles and turtles inhabited freshwater and saltwater basins. Large lizards with long spikes on their backs and huge pythons lived on the territory of modern Europe.

Of the terrestrial reptiles for the Cretaceous period, trachodons and horned lizards were especially characteristic. Trachodons could move both on two and on four legs. Between the fingers they had membranes that helped them swim. The jaws of trachodons 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 animals from predators. They lived mostly in dry places. They ate vegetation.

Triceratops.

Styracosaurs had nasal outgrowths - horns and six horny spikes on the posterior edge of the bone shield. Their heads reached two meters in length. The spikes and horns made styracosaurs dangerous to many predators.

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

Tyrannosaur.

Ceratosaurus was relatively small, but fast predator. He had a small horn on his head and a bone crest on his back. Ceratosaurus moved on its hind legs, each of which had three fingers with large claws.

Torbosaurus was rather clumsy and preyed mainly on sedentary scolosaurs, reminiscent of modern armadillos in appearance. Thanks to powerful jaws and strong teeth, Torbosaurs easily gnawed through the thick bone shell of scolosaurs.

Scolosaurus.

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

Pteranodon.

There are birds that could fly well. The Archeopteryx are completely extinct. However, some birds had teeth.

In Hesperornis, a waterfowl, the long finger of the hind limbs was connected to the other three by a short swimming membrane. All fingers had claws. From the forelimbs, only slightly bent humerus in the form of a thin stick remained. Hesperornis had 96 teeth. The 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, in the water he felt free. He dived well, and it was very difficult for the fish to avoid his sharp teeth.

Hesperornis.

Ichthyornis, contemporaries of the Hesperornis, were the size of a dove. They flew well. Their wings were strongly developed, and the sternum had a high keel, to which powerful pectoral muscles were attached. The beak of the Ichthyornis had many small, recurved teeth. The small brain of ichthyornis resembled the brain of reptiles.

Ichthyornis.

In the late Cretaceous period, toothless birds appear, whose relatives - flamingos - exist in our time.

Amphibians are no different from modern ones. And mammals are represented by predators 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 cenozoic era when they died out giant reptiles, mammals widely settled on 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, which appeared in abundance at the end of the Cretaceous period. Predatory mammals exterminated dinosaurs, and herbivores intercepted plant food from them. large group mammals fed on 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. Cooling and droughts led to a sharp decrease in the number of plants on Earth, as a result of which the dinosaur giants began to feel a lack of food. They perished. And predators, for which dinosaurs served as prey, also died, because they had nothing to eat. Perhaps the heat of the sun was not enough for the embryos to mature in the eggs of dinosaurs. In addition, the cold snap 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 in cold weather they moved sluggishly, could fall into winter stupor and became easy prey for predators. Dinosaur skin did not protect them from the cold. And they almost did not care 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, 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 the eggs and fed the chicks.

Of the reptiles, those who hid from the cold in burrows that lived in warm areas survived. From them came modern lizards, snakes, turtles and crocodiles.

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

The Cretaceous period lasted 70 million years.