The periods of the Mesozoic era are. Jurassic period of the Mesozoic era. Mesozoic life

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Mesozoic era(248-65 million years ago) - the fourth epoch in the evolutionary process of the life of our planet. Its duration is 183 million years. The Mesozoic era is divided into 3 periods: Triassic, Jurassic and Cretaceous.

Periods of the Mesozoic Era

Triassic period (Triassic). The initial erathem of the Mesozoic era lasts 35 million years. This is the time of the formation of the Atlantic Ocean. The single continent of Pangea again begins to break into two parts - Gondwana and Laurasia. Inland continental water bodies begin to dry up actively. The depressions remaining from them are gradually filled with rock deposits. New mountain heights and volcanoes appear, which show increased activity. A huge part of the land is also occupied by desert zones with weather conditions unsuitable for the life of most species of living beings. Salt levels in water bodies are rising. During this time period, representatives of birds, mammals and dinosaurs appear on the planet.

Jurassic period(Yura)- the most famous period of the Mesozoic era. It got its name thanks to the sedimentary deposits of that time found in the Jura (mountains of Europe). The average period of the Mesozoic era lasts about 69 million years. The formation of modern continents begins - Africa, America, Antarctica, Australia. But they are not yet in the order to which we are accustomed. Deep bays and small seas appear, separating the continents. The active formation of mountain ranges continues. The Arctic Sea floods the north of Laurasia. As a result, the climate is humidified, and vegetation forms on the site of deserts.

Cretaceous (Cretaceous). The final period of the Mesozoic era takes a time interval of 79 million years. Angiosperms appear. As a result of this, the evolution of representatives of the fauna begins. The movement of the continents continues - Africa, America, India and Australia are moving away from each other. The continents of Laurasia and Gondwana begin to disintegrate into continental blocks. Huge islands are formed in the south of the planet. The Atlantic Ocean is expanding. The Cretaceous period is the heyday of flora and fauna on land. In connection with the evolution flora, fewer minerals enter the seas and oceans. The number of algae and bacteria in water bodies is reduced.

In details periods of the mesozoic era will be considered in the following lectures.

The climate of the Mesozoic era

The climate of the Mesozoic era at the very beginning there was one on the whole planet. The air temperature at the equator and the poles was kept at the same level. At the end of the first period of the Mesozoic era, a drought reigned on Earth for most of the year, which was briefly replaced by rainy seasons. But, despite the arid conditions, the climate became much colder than it was during the Paleozoic period. Some species of reptiles have fully adapted to cold weather. Mammals and birds would later evolve from these animal species.

In the Cretaceous, it gets even colder. All continents have their own climate. Tree-like plants appear, which lose their foliage during the cold season. Snow begins to fall at the North Pole.

Plants of the Mesozoic Era

At the beginning of the Mesozoic, the continents were dominated by club mosses, various ferns, the ancestors of modern palms, conifers and ginkgo trees. In the seas and oceans, the dominance belonged to the algae that formed the reefs.

The increased humidity of the climate of the Jurassic period led to the rapid formation of the plant mass of the planet. The forests consisted of ferns, conifers and cycads. Tui and araucaria grew near water bodies. In the middle of the Mesozoic era, two belts of vegetation formed:

1. Northern, dominated by herbaceous ferns and ginkgo trees;
2. Southern. Tree ferns and cicadas reigned here.

In the modern world, ferns, cycads (palm trees reaching a size of 18 meters) and cordaites of that time can be found in tropical and subtropical forests. Horsetails, club mosses, cypresses and spruce trees practically did not have any differences from those that are common in our time.

The Cretaceous period is characterized by the appearance of plants with flowers. In this regard, butterflies and bees appeared among insects, thanks to which flowering plants could quickly spread across the planet. Also at this time, ginkgo trees begin to grow with foliage falling in the cold season. Conifers woodlands of this time period are very similar to modern ones. They include yews, firs and cypresses.

The development of higher gymnosperms lasts throughout the Mesozoic era. These representatives have their name earth flora obtained due to the fact that their seeds did not have an outer protective shell. The most widespread are cycads and bennettites. In appearance, cycads resemble tree ferns or cycads. They have straight stems and massive feather-like leaves. Bennettites are trees or shrubs. Outwardly similar to cycads, but their seeds are covered with a shell. This brings plants closer to angiosperms.

In the Cretaceous, angiosperms appear. From this moment begins a new stage in the development plant life. Angiosperms (flowering) are at the top rung of the evolutionary ladder. They have special reproductive organs - stamens and pistil, which are located in the flower bowl. Their seeds, unlike gymnosperms, hide a dense protective shell. These mesozoic era plants quickly adapt to any climatic conditions and are actively developing. Per short term angiosperms began to dominate the entire Earth. Their various types and forms have reached modern world- eucalyptus, magnolias, quince, oleanders, walnut trees, oaks, birches, willows and beeches. Of the gymnosperms of the Mesozoic era, now we are only familiar with coniferous species - fir, pine, sequoia and some others. The evolution of plant life of that period significantly overtook the development of representatives of the animal world.

Animals of the Mesozoic Era

Animals in the Triassic period of the Mesozoic era actively evolved. A huge variety of more developed creatures was formed, which gradually replaced the ancient species.

One of these types of reptiles was pelycosaurs, similar to animals - sailing lizards. On their backs was a huge sail, similar to a fan. They were replaced by therapsids, which were divided into 2 groups - predators and herbivores. Their paws were powerful, their tails were short. In terms of speed and endurance, therapsids far surpassed pelycosaurs, but this did not save their species from extinction at the end of the Mesozoic era.

The evolutionary group of lizards, from which mammals would later emerge, are the cynodonts (dog teeth). These animals got their name due to powerful jaw bones and sharp teeth, with which they could easily chew raw meat. Their bodies were covered with thick fur. Females laid eggs, but newborn cubs fed on mother's milk.

At the beginning of the Mesozoic era, a new species of lizards formed - archosaurs (ruling reptiles). They are the ancestors of all dinosaurs, pterosaurs, plesiosaurs, ichthyosaurs, placodonts, and crocodylomorphs. Archosaurs, adapted to the climatic conditions on the coast, became predatory thecodonts. They hunted on land near water bodies. Most thecodonts walked on 4 legs. But there were also individuals who ran on their hind legs. In this way, these animals developed incredible speed. Over time, thecodonts evolved into dinosaurs.

By the end of the Triassic period, 2 species of reptiles dominated. Some are the ancestors of the crocodiles of our time. Others have become dinosaurs.

Dinosaurs are not like other lizards in body structure. Their paws are located under the body. This feature allowed the dinosaurs to move quickly. Their skin is covered with waterproof scales. Lizards move on 2 or 4 legs, depending on the species. The first representatives were fast coelophyses, powerful herrerasaurs and huge plateosaurs.

In addition to dinosaurs, archosaurs gave rise to another type of reptile that is different from the rest. These are pterosaurs - the first pangolins that can fly. They lived near water bodies, and ate various insects for food.

Animal world sea ​​depths The Mesozoic era is also characterized by a variety of species - ammonites, bivalves, shark families, bony and ray-finned fish. The most outstanding predators were the underwater lizards that appeared not so long ago. Dolphin-like ichthyosaurs had high speed. One of the giant representatives of ichthyosaurs is Shonisaurus. Its length reached 23 meters, and its weight did not exceed 40 tons.

Lizard-like notosaurs had sharp fangs. Plakadonts, similar to modern newts, searched the seabed for mollusk shells, which they bit with their teeth. Tanystrophei lived on land. Long (2-3 times the size of the body), slender necks allowed them to catch fish standing on the shore.

Another group of marine dinosaurs of the Triassic period are plesiosaurs. At the beginning of the era, plesiosaurs reached a size of only 2 meters, and by the middle of the Mesozoic evolved into giants.

The Jurassic period is the time of the development of dinosaurs. The evolution of plant life gave impetus to the emergence of different types of herbivorous dinosaurs. And this, in turn, led to an increase in the number of predatory individuals. Some types of dinosaurs were the size of a cat, while others were as large as giant whales. by the most giant specimens are diplodocus and brachiosaurus, reaching a length of 30 meters. Their weight was about 50 tons.

Archeopteryx is the first creature to stand on the border between lizards and birds. Archeopteryx did not yet know how to fly long distances. Their beaks were replaced by jaws with sharp teeth. The wings ended in fingers. Archeopteryx were the size of modern crows. They lived mainly in forests, and ate insects and various seeds.

In the middle of the Mesozoic era, pterosaurs are divided into 2 groups - pterodactyls and rhamphorhynchus. Pterodactyls lacked a tail and feathers. But there were large wings and a narrow skull with a few teeth. These creatures lived in flocks on the coast. During the day they hunted for food, and at night they hid in the trees. Pterodactyls ate fish, shellfish and insects. To take to the skies, this group of pterosaurs had to jump from high places. Ramphorhynchus also lived on the coast. They ate fish and insects. They had long tails, which had a blade at the end, narrow wings and a massive skull with teeth of different sizes, which were convenient for catching slippery fish.

The most dangerous predator of the deep sea was Liopleurodon, which weighed 25 tons. Huge Coral reefs, in which ammonites, belemnites, sponges and sea mats settled. Representatives of the shark family develop and bony fish. New species of plesiosaurs and ichthyosaurs appeared, sea ​​turtles and crocodiles. Saltwater crocodiles have flippers instead of legs. This feature allowed them to increase their speed in the aquatic environment.

During the Cretaceous period of the Mesozoic era there were bees and butterflies. Insects carried pollen, and flowers gave them food. Thus began a long-term cooperation between insects and plants.

by the most famous dinosaurs of that time were predatory tyrannosaurs and tarbosaurs, herbivorous bipedal iguanodons, quadrupedal rhinoceros-like triceratops and small armored ankylosaurs.

Most of the mammals of that period belong to the subclass Allotherium. These are small animals, similar to mice, weighing no more than 0.5 kg. The only exceptional species is repenomamas. They grew up to 1 meter and weighed 14 kg. At the end of the Mesozoic era, the evolution of mammals takes place - the ancestors of modern animals are separated from allotheria. They were divided into 3 types - oviparous, marsupial and placental. It is they who at the beginning of the next era replace the dinosaurs. From the placental species of mammals, rodents and primates appeared. Purgatorius became the first primates. From the marsupial species, modern opossums originated, and the egg-laying species gave rise to platypuses.

The air space is dominated by early pterodactyls and new types of flying reptiles - orcheopteryx and quetzatcoatl. These were the most gigantic flying creatures in the entire history of the development of our planet. Together with representatives of pterosaurs, birds dominate the air. In the Cretaceous period, many ancestors of modern birds appeared - ducks, geese, loons. The length of the birds was 4-150 cm, weight - from 20 g. up to several kilograms.

Huge predators reigned in the seas, reaching a length of 20 meters - ichthyosaurs, plesiosaurs and mososaurs. Plesiosaurs had very long necks and small heads. Their large size did not allow them to develop great speed. The animals ate fish and shellfish. Mososaurs replaced saltwater crocodiles. These are giant predatory lizards with an aggressive character.

At the end of the Mesozoic era, snakes and lizards appeared, the species of which have reached the modern world without changing. Turtles of this time period also did not differ from those that we see now. Their weight reached 2 tons, length - from 20 cm to 4 meters.

Towards the end Cretaceous most reptiles begin to die out en masse.

Minerals of the Mesozoic era

A large number of deposits of natural resources are associated with the Mesozoic era. These are sulfur, phosphorites, polymetals, building and combustible materials, oil and natural gas.

On the territory of Asia, in connection with active volcanic processes, the Pacific belt was formed, which gave the world large deposits of gold, lead, zinc, tin, arsenic and other types of rare metals. In terms of coal reserves, the Mesozoic era is significantly inferior to Paleozoic era, but even during this period several large deposits of brown and hard coal were formed - the Kansk basin, Bureinsky, Lensky.

Mesozoic oil and gas fields are located in the Urals, Siberia, Yakutia, Sahara. Phosphorite deposits have been found in the Volga and Moscow regions.

Speaking of the Mesozoic era, we come to the main topic of our site. The Mesozoic era is also called the era average life. That rich, varied and mysterious life, which developed, changed, and finally ended about 65 million years ago. The beginning is about 250 million years ago. ending about 65 million years ago
The Mesozoic era lasted approximately 185 million years. It is usually divided into three periods:
Triassic
Jurassic period
Cretaceous
The Triassic and Jurassic periods were much shorter than the Cretaceous, which lasted about 71 million years.

Georgaffia and tectonics of the planet in the Mesozoic era

At the end of the Paleozoic era, the continents occupied vast expanses. The land prevailed over the sea. All the ancient platforms that form the land were elevated above sea level and surrounded by folded mountain systems formed as a result of Varisian folding. The East European and Siberian platforms were connected by the newly emerged mountain systems of the Urals, Kazakhstan, Tien Shan, Altai and Mongolia; the land area has greatly increased due to the formation of mountainous regions in Western Europe, as well as along the edges of the ancient platforms of Australia, North America, South America (Andes). In the Southern Hemisphere there was a huge ancient continent Gondwana.
In the Mesozoic, the disintegration of the ancient continent of Gondwana began, but in general the Mesozoic era was an era of relative calm, only occasionally and briefly disturbed by minor geological activity called folding.
With the onset of the Mesozoic, the land began to sink, accompanied by the advance (transgression) of the sea. The mainland Gondwana split and broke up into separate continents: Africa, South America, Australia, Antarctica and the massif of the Hindustan Peninsula.

Within Southern Europe and Southwestern Asia, deep troughs began to form - the geosynclines of the Alpine folded region. The same troughs, but on the oceanic crust, arose along the periphery of the Pacific Ocean. Transgression (advance) of the sea, expansion and deepening of geosynclinal troughs continued during the Cretaceous period. Only at the very end of the Mesozoic era does the rise of the continents and the reduction in the area of ​​the seas begin.

Climate in the Mesozoic Era

The climate in different periods changed depending on the movement of the continents. In general, the climate was warmer than now. At the same time, it was approximately the same on the entire planet. There was no such temperature difference between the equator and the poles as it is now. Apparently this is due to the location of the continents in the Mesozoic era.
Seas and mountains appeared and disappeared. AT Triassic period dry climate. This is due to the location of the land, most of which was desert. Vegetation existed along the coast of the ocean and along the banks of rivers.
In the Jurassic, when the mainland Gondwana split and its parts began to diverge, the climate became more humid, but remained warm and even. Such climate change has become an impetus for the development of lush vegetation and rich wildlife.
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 woody plants appear, which partially or completely shed their leaves during the cold seasons. This feature of plants is an adaptation to a colder climate.

Flora in the Mesozoic Era

At the beginning of the Cretaceous, gymnosperms are still widespread, but the first angiosperms, more advanced forms, are already appearing.
The flora of the Lower Cretaceous still resembles in composition the vegetation of the Jurassic period. Gymnosperms are still widespread, but their dominance ends by the end of this time. Even in the Lower Cretaceous, the most progressive plants suddenly appeared - angiosperms, the predominance of which characterizes the era of new plant life. which we now know.
Angiosperms, or flowering plants, occupy the highest rung of the evolutionary ladder of the plant world. Their seeds are enclosed in a strong shell; there are specialized reproductive organs (stamen and pistil), collected in a flower with bright petals and a calyx. Flowering plants appear somewhere in the first half of the Cretaceous period, most likely in a cold and arid mountain climate with large temperature fluctuations. With the gradual cooling, which began in the Cretaceous period, flowering plants captured more and more new areas on the plains. Quickly adapting to the new environment, they developed at great speed.
Within a relatively short time, flowering plants spread throughout the Earth and reached a great diversity. From the end of the Early Cretaceous, the balance of power began to change in favor of angiosperms, and by the beginning of the Upper Cretaceous, their superiority became widespread. Cretaceous angiosperms belonged to evergreen, tropical or subtropical types, among them were eucalyptus, magnolia, sassafras, tulip trees, Japanese quince trees (quince), brown laurels, walnut trees, plane trees, oleanders. These heat-loving trees coexisted with the typical flora of the temperate zone: oaks, beeches, willows, birches. This flora also included gymnosperms of conifers (sequoias, pines, etc.).
For the gymnosperms, it was a time of surrender. Some species have survived to this day, but their total number has been descending all these centuries. A definite exception is conifers, which are found in abundance today. In the Mesozoic, plants made a great leap forward, surpassing animals in terms of development.

Animal world of the Mesozoic era.

Reptiles.

The oldest and most primitive reptiles were clumsy cotylosaurs, which appeared already at the beginning of the Middle Carboniferous and became extinct by the end of the Triassic. Among cotylosaurs, both small animal-eating and relatively large herbivorous forms (pareiasaurs) are known. The descendants of cotilosaurs gave rise to the whole diversity of the world of reptiles. One of the most interesting groups of reptiles that developed from the cotylosaurs were the animal-like ones (Synapsida, or Theromorpha); their primitive representatives (pelycosaurs) have been known since the end of the Middle Carboniferous. In the middle of the Permian period, the pelycosaurs that inhabited the territory of present-day North America die out, but in the European part they are replaced by more developed forms forming the Therapsida order.
The carnivorous theriodonts (Theriodontia) included in it have some similarities with mammals. By the end of the Triassic period, it was from them that the first mammals developed.
During the Triassic period, many new groups of reptiles appeared. These are turtles, and ichthyosaurs ("lizard fish"), well adapted to life in the sea, outwardly resembling dolphins. Placodonts, clumsy armored animals with powerful flat-shaped teeth adapted for crushing shells, and also plesiosaurs living in the seas, which had a relatively small head and a long neck, a wide body, flipper-like paired limbs and a short tail; Plesiosaurs vaguely resemble giant tortoises without a shell.

Dinosaurs

In the Triassic, they still competed with animals that survived the Permian catastrophe, but in the Jurassic and Cretaceous periods they were confidently leading in all ecological niches. Currently, about 400 species of dinosaurs are known.
Dinosaurs are represented by two groups, saurischia (Saurischia) and ornithischia (Ornithischia).
In the Triassic, the diversity of dinosaurs was not great. The earliest known dinosaurs were eoraptor and herrerasaurus. The most famous of the Triassic dinosaurs are coelophysis and Plateosaurus .
The Jurassic period is known for the most amazing diversity among dinosaurs; real monsters could be found, up to 25-30 m long (with a tail) and weighing up to 50 tons. Of these giants, the most famous diplodocus and brachiosaurus. Also a striking representative of the Jurassic fauna is a bizarre stegosaurus. It can be unmistakably identified among other dinosaurs.
In the Cretaceous period, the evolutionary progress of dinosaurs continued. Of the European dinosaurs of this time, bipeds are widely known. iguanodons, four-legged horned dinosaurs became widespread in America triceratops similar to modern rhinos. In the Cretaceous, relatively small armored dinosaurs also existed - ankylosaurs, covered with a massive bone shell. All these forms were herbivorous, as were the giant duck-billed dinosaurs such as the anatosaurus and trachodon, which walked on two legs.
In addition to herbivores, carnivorous dinosaurs also represented a large group. All of them belonged to the group of lizards. A group of carnivorous dinosaurs are called terrapods. In the Triassic, this is Coelophysis - one of the first dinosaurs. In the Jurassic, this Allosaurus and Deinonychus reached their present flowering. In the Cretaceous period, the most remarkable were such forms as Tyrannosaurus ( Tyrannosaurus rex), whose length exceeded 15 m, Spinosaurus and Tarbosaurus. All these forms, which turned out to be the greatest land predatory animals in the entire history of the Earth, moved on two legs.

Other reptiles of the Mesozoic era

At the end of the Triassic, the first crocodiles also originated from thecodonts, which became abundant only in the Jurassic (Steneosaurus and others). In the Jurassic, flying lizards appear - pterosaurs (Pterosaurid), also descended from thecodonts. Among the flying lizards of the Jura, the most famous are the rhamphorhynchus (Rhamphorhynchus) and the pterodactyl (Pterodactylus), of the Cretaceous forms, the relatively very large Pteranodon (Pteranodon) is the most interesting. Flying pangolins become extinct by the end of the Cretaceous.
In the Cretaceous seas, giant predatory lizards - mosasaurs, exceeding 10 m in length, became widespread. Among modern lizards, they are closest to monitor lizards, but differ from them, in particular, in flipper-like limbs. By the end of the Cretaceous, the first snakes (Ophidia) also appeared, apparently descended from burrowing lizards. By the end of the Cretaceous, the mass extinction of characteristic Mesozoic groups of reptiles, including dinosaurs, ichthyosaurs, plesiosaurs, pterosaurs and mosasaurs, occurs.

Cephalopods.

Belemnite shells are popularly known as "devil's fingers". Ammonites were found in the Mesozoic in such quantities that their shells are found in almost all marine sediments of this time. Ammonites appeared as early as the Silurian, they experienced their first heyday in the Devonian, but reached their highest diversity in the Mesozoic. In the Triassic alone, more than 400 new genera of ammonites arose. Particularly characteristic of the Triassic were the ceratids, which were widely distributed in the Upper Triassic marine basin of Central Europe, the deposits of which are known in Germany as shell limestone. By the end of the Triassic, most ancient groups of ammonites die out, but representatives of phylloceratids (Phylloceratida) have survived in Tethys, the giant Mesozoic Mediterranean Sea. This group developed so rapidly in the Jurassic that the ammonites of this time surpassed the Triassic in the variety of forms. In the Cretaceous, cephalopods, both ammonites and belemnites, are still numerous, but in the course of the Late Cretaceous, the number of species in both groups begins to decline. Among ammonites at this time, aberrant forms with an incompletely twisted hook-shaped shell with a shell elongated in a straight line (Baculites) and with an irregularly shaped shell (Heteroceras) appear. These aberrant forms appeared, most likely, as a result of changes in the course of individual development and narrow specialization. The final Upper Cretaceous forms of some ammonite branches are distinguished by sharply increased shell sizes. In one of the ammonite species, the shell diameter reaches 2.5 m. Great importance in the Mesozoic era acquired belemnites. Some of their genera, such as Actinocamax and Belemnitella, are important as guide fossils and are successfully used for stratigraphic subdivision and accurate age determination of marine sediments. At the end of the Mesozoic, all ammonites and belemnites became extinct. Of the cephalopods with an outer shell, only nautiluses have survived to this day. Forms with an internal shell are more widely distributed in modern seas - octopuses, cuttlefish and squids, remotely related to belemnites.

Other invertebrates of the Mesozoic era.

Tabulata and four-beam corals were no longer in the Mesozoic seas. Their place was taken by six-ray corals (Hexacoralla), whose colonies were active reef-formers - the marine reefs built by them are now widely distributed in pacific ocean. Some groups of brachiopods still evolved in the Mesozoic, such as the Terebratulacea and Rhynchonellelacea, but the vast majority of them declined. 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 (Echinoidca) have made the most progress; today
a day from the Mesozoic, countless species of them are described. were plentiful sea ​​stars(Asteroidea) and ophidras.
Compared to the Paleozoic era, bivalve mollusks also spread greatly in the Mesozoic. Already in the Triassic, many of their new genera appeared (Pseudomonotis, Pteria, Daonella, etc.). At the beginning of this period, we also meet the first oysters, which later become one of the most common groups of molluscs in the Mesozoic seas. The appearance of new groups of molluscs continues into the Jurassic, the characteristic genera of this time being Trigonia and Gryphaea, classified as oysters. In the Cretaceous formations one can find funny types of bivalves - rudists, whose cup-shaped shells had a special cap at the base. These creatures settled in colonies, and in the Late Cretaceous they contributed to the construction of limestone cliffs (for example, the genus Hippurites). The most characteristic bivalves of the Cretaceous were molluscs of the genus Inoceramus; some species of this genus reached 50 cm in length. In some places there are significant accumulations of remains of Mesozoic gastropods (Gastropoda).
During the Jurassic period, the foraminifera flourished again, surviving the Cretaceous period and reaching modern times. In general, unicellular protozoa were an important component in the formation of sedimentary
Mesozoic rocks, and today they help us to establish the age of various layers. The Cretaceous period was also a time of rapid development of new types of sponges and some arthropods, in particular insects and decapods.

The rise of vertebrates. Mesozoic fish.

The Mesozoic era was a time of unstoppable expansion of vertebrates. Of the Paleozoic fishes, only a few passed into the Mesozoic, as did the genus Xenacanthus, the last representative of freshwater sharks Paleozoic known from freshwater deposits of the Australian Triassic. Sea sharks continued to evolve throughout the Mesozoic; most modern genera were already represented in the seas of the Cretaceous, in particular Carcharias, Carcharodon, Isurus, etc. The ray-finned fish that arose at the end of the Silurian originally lived only in freshwater reservoirs, but from the Permian they begin to enter the seas, where they multiply unusually and from the Triassic to the present day they retain their dominant position. Earlier, we already talked about the Paleozoic lobe-finned fish, from which the first terrestrial vertebrates developed. Almost all of them died out in the Mesozoic; only a few of their genera (Macropoma, Mawsonia) were found in the Cretaceous rocks. Up until 1938, paleontologists believed that the crossopterygians had become 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 have studied this unique fish, came to the conclusion that it belongs to the "extinct" group of crossopterygians (Coelacanthida). Before
to date, this species remains the only modern representative of ancient lobe-finned fish. It received the name Latimeria chalumnae. Such biological phenomena are referred to as "living fossils".

Amphibians.

In some zones of the Triassic, labyrinthodonts (Mastodonsaurus, Trematosaurus, etc.) are still numerous. By the end of the Triassic, these "armored" amphibians disappear from the face of the earth, but some of them, apparently, gave rise to the ancestors of modern frogs. We are talking about the genus Triadobatrachus; to date, only one incomplete skeleton of this animal has been found in the north of Madagascar. In the Jurassic, true anurans are already found
- Anura (frogs): Neusibatrachus and Eodiscoglossus in Spain, Notobatrachus and Vieraella in South America. In the Cretaceous, the development of tailless amphibians accelerates, but they reach the greatest diversity in the Tertiary period and now. In the Jurassic, the first tailed amphibians (Urodela) also appear, to which modern newts and salamanders belong. Only in the Cretaceous did their finds become more common, while the group reached its peak only in the Cenozoic.

First birds.

Representatives of the bird class (Aves) first appear in the Jurassic deposits. The remains of Archeopteryx (Archaeopteryx), a widely known and so far the only known first bird, were found in Upper Jurassic lithographic shale, near the Bavarian city of Solnhofen (Germany). During the Cretaceous, bird evolution proceeded at a rapid pace; genera characteristic of this time were ichthyornis (Ichthyornis) and hesperornis (Hesperornis), which still had serrated jaws.

The first mammals

The first mammals (Mammalia), modest animals, no larger than 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. The most ancient group of mammals were triconodonts (Triconodonta), to which the most famous of the Triassic mammals Morganucodon belongs. In the Jurassic, a number of new groups of mammals appear.
Of all these groups, only a few survived the Mesozoic, the last of which die out in the Eocene. The ancestors of the main groups of modern mammals - marsupials (Marsupialia) and placental (Placentalid) were Eupantotheria. Both marsupials and placentals appeared at the end of the Cretaceous. Most ancient group placental are insectivorous (Insectivora), preserved in our time. Powerful tectonic processes of Alpine folding, which erected new mountain ranges and changed the outlines of continents, radically changed the geographical and climatic situation. Almost all Mesozoic groups of the animal and plant kingdoms retreat, die out, disappear; on the ruins of the old, a new world arises, the world of the Cenozoic era, in which life receives a new impetus to development and, in the end, the living species of organisms are formed.

Kaytsukov A.A. one

Konstantinova M.V. one Boeva ​​E.A. 1

1 Municipal budgetary educational institution secondary school 5 Odintsovo

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Introduction

The environment is very rich and varied. We are surrounded by living and inanimate nature. Nature is a beautiful, mysterious, and sometimes little-studied and unknown world. The history of dinosaurs is very interesting, as it represents a huge era in the life of our planet, in comparison with which human history looks like an instant. But no one can say for sure what color and type these amazing animals were, why some species died out, while others appeared, why suddenly at the end of the Cretaceous period these animals disappeared altogether from the face of the Earth. You can only speculate and study, study, study. One such little-studied page of wildlife includes information about dinosaurs - animals that lived on our planet long before the appearance of man.

From the early childhood I liked watching shows about dinosaurs.

My parents began to buy books for me. First of all, I looked for pages in them that talk about dinosaurs, I looked at drawings with dinosaurs, I was interested in how they look, I liked to draw them. When I learned to read, I wanted to understand how they lived, what they looked like, why they died out and whether they had relatives in our world. After all, many modern animals look like dinosaurs. I wanted to know more about them.

For example:

how do people learn about the life of dinosaurs?

When did dinosaurs live? How did they appear on our planet?

What did they look like, what did they eat?

Why did dinosaurs become extinct?

I will try to answer all these questions in my study.

Purpose of the study : Analyze known scientific facts about the life of dinosaurs, behavior, reproduction and causes of extinction, find and highlight signs of herbivores and predators. And determine the cause of their death. Having studied the available information about the world of dinosaurs, I will try to justify. Dinosaurs - who are they?

Tasks:

1. To study the Triassic periods of the Mesozoic era, the features of the animal and plant world of each period.

2. The Jurassic period is the middle period of the Mesozoic era.

3. The Cretaceous period is the last period of the Mesozoic era, followed by the Paleogene period of the Cenozoic era.

Hypothesis: The reason for the death of dinosaurs. The extinction of dinosaurs as a result of a sharp climate change on our planet.

Chapter 1. Mesozoic era. The era of dinosaurs.

For many years, people thought that the world they live in was created in the state it appears to be in today. And the age of the Earth was considered equal to several thousand years. But relatively recently, it was proved that the age of our planet exceeds 6 billion years, and, accordingly, life originated a very, very long time ago. It arose by chance, by a unique set of circumstances, and continued to progress. Some forms of life were replaced by new, more perfect ones, which, having existed for thousands and millions of years, disappeared in the abyss of time.

Triassic

The first of three periods of the Mesozoic era. The Triassic period in the history of the Earth marked the beginning of the Mesozoic era. The Triassic period is the time when the remains of the animal world, preserved from the Permian period, were replaced by new, revolutionary animal species. The Triassic period is the time when the first dinosaurs appeared. Although some of the life forms of the Permian period existed throughout the Mesozoic era and died out along with the dinosaurs.

Triassic period tectonics:

Back to top Triassic period On Earth there was a single continent - Pangea. During Triassic period, Pangea broke up into two continents, Laurasia in the northern part and Gondwana in the southern. The great bay, which began in the east of Gondwana, stretched 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 arose on Gondwana, gradually filled with continental deposits. The Atlantic Ocean began to form. The continents were interconnected. The land prevailed over the sea. The level of salinity in the seas has increased. In the middle of the Triassic period, volcanic activity intensified. Inland seas dry up, form deep depressions. Along with changes in the distribution of sea and land, new mountain ranges and volcanic regions were formed. AT Triassic period vast areas were covered with deserts with harsh conditions for animal life. Life seethed only along the banks of reservoirs.

Triassic became a transitional period between the Paleozoic and Mesozoic. There was an intensive change of some animal and plant forms by others. Only a few families passed from the Paleozoic era to the Mesozoic. And they existed for many millions of years already in the Triassic. But at this time, new forms of reptiles appeared and developed, which replaced the old ones. At the beginning Triassic period animal world was the same throughout. Pangea was a single continent and various species could freely spread throughout the land. However, when studying the deposits of the Triassic period, one can easily be convinced 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 woody plants appear, which partially or completely shed their leaves during the cold seasons. 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 Triassic seas were inhabited by calcareous sponges, bryozoans, leaf-legged crayfish, and ostracods. 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 deposits of oil, natural gases, brown and hard coal, iron and copper ore, rock salt. 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 area Middle 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.

The Triassic period lasted 35 million years. (Appendix 1-2)

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.

Significantly common sedimentary rocks containing many representatives of fauna and flora.

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. 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. At this time, huge, the largest land animals that have ever existed on Earth appeared: Brachiosaurus, Apatosaurus, Diplodocus, Supersaurus, Ultrasaurus and Seismosaurus. Small gazelle and larger beak-nosed dinosaurs led a group lifestyle. Then came the amazing spiny dinosaurs. Most of them had a long neck, a small head and a long tail. They had two brains: one small - in the head; the second is much larger in size - at the base of the tail. The largest of jurassic dinosaurs was a brachiosaurus, reaching a length of 26 m, weighing about 50 tons. It had columnar legs, a small head, 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. Dinosaurs were extremely diverse - some were no larger than a chicken, others reached gigantic sizes. . [Ushakov's dictionary, p. 332]. Some hunted and picked up carrion, others plucked grass and swallowed stones. All of them found a mate, laid eggs and raised cubs. Dinosaurs moved in different ways: some on two, some on four legs. Many lizards swam, some even tried to fly. They had to fight, escape from pursuers, hide and die. Dinosaur fossils have been found in literally every part of the world. This suggests that dinosaurs lived all over the world. They appeared on our planet about 230 million years ago. But 65 million years ago, these wonderful animals died out. This time period (more than 160 million years) covers three periods of earth's history (Triassic, Jurassic and Cretaceous), which scientists combine into the Mesozoic era. It is often referred to as the age of the dinosaurs. Although the dinosaurs themselves have long disappeared from the face of the Earth, but the memory of them is reliably kept by stones. Studies have shown that a group of reptiles that lived about 230 million years ago acquired a new way of moving on land. Instead of crawling on legs wide apart, crouching to the ground like crocodiles, they began to walk on straight legs. Presumably these reptiles were the ancestors of all dinosaurs. The first representatives of dinosaurs originated in the Triassic period. . First typical representatives dinosaurs of that time were bipedal predators of medium size.

Soon larger and increasingly four-legged herbivorous dinosaurs appeared. Finally, at the end of this period, the first small bipedal herbivorous animals arose. 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 point in the process of turning reptiles into birds, there was a 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 feathers of the bird were bright, like those of modern tropical birds, others that the feathers were gray or brown, and still others that they were variegated. 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, and 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. 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.

The Jurassic period lasted 55 million years. (Annex 3)

1.3 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 period, 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. At high latitudes in the north during the Cretaceous period, there was already real winter with snow. Within the boundaries of the modern temperate zone, some tree species (walnut, ash, beech) did not differ in any way 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 the northern regions, subsequently they settled throughout 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. The climate of ancient Europe became tropical, and forests similar to modern jungles 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 of various shapes and colors spread.

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 curled up in the summer heat.

Plants spread throughout Greenland and the islands of the 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 the ammonites still continued to multiply at a high rate, 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 a sharp change in physical and geographical conditions in the Cretaceous.

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 wing 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 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 taken place among the fish. In the seas of the Cretaceous period, ganoid fish are gradually dying out. The number is increasing bony fish(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. On the territory of modern Europe lived big lizards with long spikes on the back and huge pythons.

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. 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 footprints were left, 80 cm long. The step of the tyrannosaurus was 4 m. 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. Birds appeared that could fly well. The Archeopteryx are completely extinct. However, some birds had teeth.

In Hesperornis - 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. In the late Cretaceous period, toothless birds appeared, whose relatives - flamingos - exist in our time. 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, warm weather they were active, but in the cold they moved sluggishly, could fall into winter stupor and become 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.

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

The Cretaceous period lasted 70 million years. (Appendix 4.)

Chapter 2. Reasons for the death of dinosaurs. According to paleontologists, dinosaurs became extinct about 65 million years ago.

Scientists put forward various hypotheses about the causes of the death of dinosaurs:

Asteroid impact - about 65 million years ago, an asteroid collided with the Earth. this led to the formation of a dust cloud that closed the Earth from direct sunlight and caused a cooling on the planet.

Increasing volcanic activity, which led to the release of large amounts of ash into the atmosphere, which closed the Earth from direct sunlight, which caused a sharp cooling.

A sharp change in the polarity of the Earth's magnetic field.

An excess of oxygen in the atmosphere and water of the Earth, which exceeded its threshold content for dinosaurs, that is, they simply poisoned them.

Large-scale epidemic among dinosaurs.

The emergence of flowering plants - dinosaurs could not adapt to the change in the type of vegetation.

All these reasons can be divided into two opposing points of view:

Dinosaurs were killed by some planetary upheaval.

Dinosaurs simply "did not keep up" with the usual, but steady change in the Earth's biosphere.

In modern paleontology, the biospheric version of the extinction of dinosaurs dominates - this is the appearance of flowering plants and a gradual change in climate. At the same time, insects that feed on flowering plants appeared, and pre-existing insects began to die out.

Animals actively adapted to feeding on green mass. Small mammals appeared, the food of which was only plants. This led to the appearance of corresponding predators, which also became mammals. Small-sized mammalian predators were harmless to adult dinosaurs, but fed on their eggs and young, making it difficult for dinosaurs to reproduce.

As a result, unfavorable conditions were created, which led to the cessation of the emergence of new species. The "old" types of dinosaurs existed for some time, but gradually died out completely. Simultaneously with the dinosaurs, marine reptiles, all flying lizards, many mollusks and other inhabitants of the sea, very different from them in their way of life, died out.

It can also be assumed that the dinosaurs did not die out at all, but made an evolutionary development. Thus, the American paleontologist John Ostrom came to the sensational conclusion that birds descend directly from small predatory running dinosaurs. He came to this conclusion when he compared the skulls of dinosaurs and modern birds. In his opinion, birds are the descendants of not even one, but several branches of dinosaurs.

While excavating, scientists discovered hundreds of different types of dinosaurs. The researchers managed to restore the skeletons of these animals and recreate a picture of their life. Today, there are museums in many parts of the world displaying dinosaur specimens. In Russia, the remains of dinosaurs can be seen in the paleontological museum named after Yu.A. Orlova in Moscow. This is one of the largest natural history museums in the world with a rich collection of dinosaur fossils. In 1815, in England, not far from Oxford, in a quarry where lime was mined, fossilized bones of a giant reptile were discovered. In 1842, the English scientist Richard Owen first used the term "dinosaurs" (terrible lizards) to refer to animals whose three fossilized skeletons were somewhat different from other pre-reptile skeletons found.

Conclusion.

From all of the above, the following conclusions can be drawn: Dinosaurs lived on earth for a long time (about 160 million years), long before the appearance of man;

Over a thousand species of dinosaurs existed on Earth during this period;

Dinosaurs became extinct as a result of severe climatic changes.

When we started research on the topic, I had to go through a large number of books and magazines dedicated to the Mesozoic era - the DINOSAUR ERA. It turns out that hundreds more questions can be answered on this topic. Therefore, we will continue this work.

Literature:

1M. Avdonina, "Dinosaurs". Complete Encyclopedia, Moscow: Eksmo, 2007.

2.David Burney, translated from English by I.D. Andrianova, Children's Encyclopedia "Prehistoric World";

3.K. Clarke, These Amazing Dinosaurs and Other Prehistoric Animals, Machaon Publishing, 1998.

4. Roger Kut, translated from English by E.V. Komissarova, I want to know everything “Dinosaurs and Planet Earth”;

5. Sheremetyeva “Dinosaurs. What? What for? Why?"

6.https://ru.wikipedia.org/wiki/Likho

7.https://yandex.ru/images/search

8. Dictionary of Ushakov, p. 332

Attachment 1.

Mesozoic era. Dinosaur era.

Appendix 2

Triassic

Annex 3

Jurassic period

Appendix 4

Cretaceous period

The Mesozoic era is a time of significant changes in the earth's crust and evolutionary progress. Over 200 million years, the main continents formed, mountain ranges. Significant was the development of life in the Mesozoic era. Thanks to warm weather conditions, wildlife was replenished with new species that became the ancestors of modern representatives.

The Mesozoic era (245–60 million years ago) is divided into the following time periods:

• Triassic;
• Jurassic;
• chalky.

Tectonic movements in the Mesozoic

The beginning of the era coincided with the completion of the formation of the Paleozoic mountain folding. Therefore, for millions of years the situation was calm, there were no massive shifts. Only in the Cretaceous period of the Mesozoic began significant tectonic movements, the last earth changes.

At the end of the Paleozoic, the land covered a large area, dominating the world ocean in area. The platforms protruded considerably above sea level and were surrounded by old folded formations.

In the Mesozoic, the Gondwana mainland was divided into several separate continents: African, South American, Australian, and Antarctica and the Hindustan Peninsula were also formed.

Already in the Jurassic period, the water rose significantly and flooded a vast territory. The flood lasted the entire Cretaceous period, and only at the end of the era was a reduction in the area of ​​the seas, and the newly formed Mesozoic folding came to the surface.

Mountains of Mesozoic folding

1. Cordillera (North America);
2. Himalayas (Asia);
3. Verkhoyansk mountain system;
4. Kalba Highlands (Asia).

It is believed that the Himalayan mountains of those times were much higher than the present, but collapsed over time. They were formed when the Indian subcontinent collided with the Asian plate.

Fauna in the Mesozoic era

The beginning of the Mesozoic era - the Triassic and Jurassic periods - were the heyday and dominance of reptiles. Some representatives reached gigantic sizes with a body weight of up to 20 tons. Among them were both herbivores and carnivores. But even in the Permian period, animal-toothed reptiles appeared - the ancestors of mammals.

The first mammals are known from the Triassic period. At the same time, reptiles moving on their hind limbs - pseudosuchia - arose. They are considered the ancestors of birds. The first bird - Archeopteryx - appeared in the Jurassic period and continued to exist even in the Cretaceous.

Progressive development of respiratory and circulatory systems in birds and mammals, providing them with warm-bloodedness, reduced their dependence on ambient temperature and ensured settlement in all geographical latitudes.

The appearance of true birds and higher mammals dates back to the Cretaceous period, and they soon occupied a dominant position in the chordate type. This was also facilitated by the development of the nervous system, the formation of conditioned reflexes, the upbringing of offspring, and in mammals, live birth and feeding of young with milk.

A progressive feature is the differentiation of teeth in mammals, which was a prerequisite for the use of a variety of foods.

Due to divergence and idioadaptations, numerous orders, genera and species of mammals and birds have appeared.

Flora in the Mesozoic era

Triassic

Gymnosperms are widely distributed on land. Ferns, algae, psilophytes were found everywhere. This was due to the fact that a new method of fertilization appeared that was not associated with water, and the formation of the seed made it possible for plant embryos to survive for a long time under adverse conditions.

As a result of the adaptations that arose, seed plants could exist not only near wet coasts, but also penetrate deep into the continents. Gymnosperms occupied a dominant place at the beginning of the Mesozoic. The most common species is the cicada. These plants are like trees with straight stems and feathery leaves. They resembled tree ferns or palm trees.

Conifers (Pine, Cypress) began to spread. Horsetails of small sizes grew in wetlands.

Jurassic period

Cretaceous period

Among angiosperms in the Cretaceous period of the great development reached Magnolia (tulip liriodendron), Pink, Kutrovye. Representatives of the Beech and Birch families grew in temperate latitudes.

As a result of divergence in the type of angiosperms, two classes were formed: monocots and dicots, and thanks to idioadaptations, numerous diverse adaptations to pollination were developed in these classes.

At the end of the Mesozoic, due to the dryness of the climate, the extinction of gymnosperms began, and since they were the main food for many, especially large reptiles, this also led to their extinction.

Features of the development of life in the Mesozoic

• Tectonic movements were less pronounced than in the Paleozoic. An important event is the division of the supercontinent Pangea into Laurasia and Gondwana.
• Throughout the era, hot weather persisted, the temperature varied between 25-35 ° C in tropical and 35-45 ° C in subtropical latitudes. The warmest period on our planet.
• The animal world developed rapidly, the Mesozoic era gave birth to the first lower mammals. There is an improvement at the system level. The development of cortical structures influenced the behavioral responses of animals and adaptive capabilities. The spinal column was divided into vertebrae, two circles of blood circulation formed.
• The development of life in the Mesozoic era was significantly influenced by the climate, so the drought of the first half of the Mesozoic era contributed to the development of seed-bearing and reptiles that are resistant to adverse conditions and water shortages. In the middle of the second period of the Mesozoic, humidity increased, which led to the rapid growth of plants and the appearance of flowering plants.

Mesozoic - an era of tectonic, climatic and evolutionary activity. There is a formation of the main contours of modern continents and mountain building on the periphery of the Pacific, Atlantic and Indian oceans; the division of the landmass contributed to 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 main part 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 a massive Permian-Triassic extinction, as a result of which approximately 90-96% of marine fauna and 70% of land vertebrates died. The upper limit is set at the turn of the Cretaceous and Paleogene, when another very large extinction of many groups of plants and animals occurred, most often due to the fall of a giant asteroid (the Chicxulub crater on the Yucatan Peninsula) and the “asteroid winter” that followed. Approximately 50% of all species died out, including all flightless dinosaurs.

Tectonics and paleogeography

Compared to the vigorous mountain building of the Late Paleozoic, Mesozoic tectonic deformations can be considered relatively mild. The era is 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 most of the modern Atlantic coast (for example, the east 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 practically took on their modern shape. Laurasia split into Eurasia and North America, Gondwana split into South America, Africa, Australia, Antarctica, and the Indian subcontinent, whose collision with the Asian continental plate caused intense orogeny with the uplift of the Himalayan mountains.

Africa

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

Late Triassic fossils are found everywhere in Africa, but are more common in the south than in the north of the continent. As you know, the time line separating the Triassic from the Jurassic period was drawn according to global catastrophe with the mass extinction of species (Triassic-Jurassic extinction), but the African layers of this time remain poorly understood today.

Early Jurassic fossil deposits are distributed similarly to those of the Late Triassic, with more frequent outcrops in the south of the continent and fewer deposits towards the north. During the Jurassic period, such sign groups dinosaurs like sauropods and ornithopods. Paleontological layers of the middle Jurassic in Africa are poorly represented and also poorly studied.

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

In the middle of the Mesozoic, about 150-160 million years ago, Madagascar separated from Africa, while remaining connected to India and the rest of Gondwana. Fossils from Madagascar have included abelisaurs and titanosaurs.

In the early Cretaceous, a part of the land that made up India and Madagascar separated from Gondwana. In the Late Cretaceous, the divergence of India and Madagascar began, which continued until the modern outlines were reached.

Unlike Madagascar, the African mainland was tectonically relatively stable throughout the Mesozoic. And yet, despite the stability, significant changes occurred in its position relative to other continents as Pangea continued to fall 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 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 the 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 fieldwork in Malawi, argues that African fossil deposits "need more careful excavation" and are bound to prove "fertile ... for scientific discoveries."

Climate

During the last 1.1 billion years in the history of the Earth, there have been three successive ice age-warm cycles, called the 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 the cyclicity is considered to be the periodic process of connecting the continents into a single continent (Pangaea) 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 already in the Cenozoic era with the Little Ice Age, which continues to this day. For 180 million years, even in the polar regions there was no stable ice cover. The climate was mostly warm and even, without significant temperature gradients, although there was climatic zoning in the northern hemisphere. A large number of greenhouse gases in the atmosphere contributed to the uniform distribution of heat. The equatorial regions were characterized by a tropical climate (the Tethys-Pantalassa region) with average annual temperature 25–30°С. Up to 45-50°N the subtropical region (Peritethys) extended, then the moderately warm boreal belt lay further, and the polar regions were characterized by a moderately cool climate.

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

Flora and fauna

Giant ferns, tree horsetails, and club mosses are dying out. Gymnosperms, especially conifers, flourish in the Triassic. In the Jurassic, seed ferns die out and the first angiosperms appear (so far represented only by tree forms), which gradually spread to all continents. This is due to a number of advantages; angiosperms have a highly developed conducting system, which ensures the reliability of cross-pollination, the embryo is supplied with food reserves (due to double fertilization, a triploid endosperm develops) and is protected by shells, etc.

In the animal kingdom, insects and reptiles flourish. Reptiles dominate and are represented a large number forms. In the Jurassic, flying lizards appear and conquer the air. In the Cretaceous period, the specialization of reptiles continues, they reach enormous sizes. Some of the dinosaurs weighed up to 50 tons.

The parallel evolution of flowering plants and pollinating insects begins. At the end of the Cretaceous, cooling sets in, and the area of ​​near-water vegetation is reduced. 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 vacant ecological niches. In the seas, many forms of invertebrates and sea lizards are dying out.

Birds, according to most paleontologists, evolved from one of the groups of dinosaurs. The complete separation of arterial and venous blood flow determined their warm-bloodedness. 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: highly developed nervous system, especially the cerebral cortex, which provided adaptation to the conditions of existence by changing behavior, moving 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 wool, the complete separation of the circulation circles, the emergence of alveolar lungs, which increased the intensity of gas exchange and, as a result, general level 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

• Jordan N. N. development of life on earth. - M .: Enlightenment, 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 .: Thought, 1984.
• Yasamanov N.A. Ancient climates of the Earth. - L.: Gidrometeoizdat, 1985.
• Yasamanov N.A. Popular paleogeography. - M .: Thought, 1985.

Links

	Portal "Mesozoic"
	Mesozoic at Wikimedia Commons

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