What periods make up the Mesozoic era. The development of life in the Mesozoic era. Flora in the Mesozoic era

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Article topic:	Mesozoic era.
Rubric (thematic category)	Geology

The Mesozoic era, which lasts 183 million years, is divided into three periods - Triassic, Jurassic and Cretaceous. Accordingly, it is divided into systems and Mesozoic group sediments.

The Triassic system got its name due to the clear division of its sediments into three parts - Lower, Middle and Upper Triassic. Respectively, Triassic(35.0 million years) is divided into three divisions - early, middle And late.

In the Mesozoic, the continents of the Northern and Southern Hemispheres were separated by a vast sea basin elongated in the latitudinal direction. It got the name Tethys- in honor of the ancient Greek goddess of the sea.

At the beginning of the Triassic, powerful volcanic eruptions occurred in some areas of the globe. Thus, in Eastern Siberia, outpourings of basaltic magma formed a layer of basic rocks that occur in the form of huge covers. Such covers are called " traps" (Swedish " trap" - staircase). It is worth saying that they are characterized by columnar separation in the form of staircase steps. Volcanic eruptions also occurred in Mexico and Alaska, Spain and North Africa. In the Southern Hemisphere, Triassic volcanism was dramatic in New Caledonia, New Zealand, the Andes and other areas.

During the Triassic, one of the largest sea regressions in Earth's history occurred. It coincided with the beginning of a new folding, which continued throughout the Mesozoic and was called “Mesozoic”. The folded structures that emerged at this time were called “mesozoid”.

The Jurassic system is named after the Jurassic Mountains in Switzerland. During the Jurassic period, which lasted 69.0 million years, a new transgression of the sea began. But at the end of the Jurassic, mountain-building movements resumed in the region of the Tethys Ocean (Crimea, Caucasus, Himalayas, etc.) and especially noticeably in the region of the Pacific margins. Οʜᴎ led to the formation of mountain structures of the outer Pacific ring: Verkhoyansk-Kolyma, Far Eastern, Andean, Cordilleran. The folding was accompanied by active volcanic activity. In South Africa and South America (Parana River basin), large outpourings of basic trap lavas occurred at the beginning of the Jurassic. The thickness of the basalt strata here reaches more than 1000 meters.

The Cretaceous system got its name due to the fact that layers of white chalk are widespread in its sediments. The Cretaceous period lasted 79.0 million years. Its beginning coincided with an extensive marine transgression. According to one hypothesis, the northern supercontinent Laurasia at that time broke up into a number of separate continents: East Asian, North European, North American. Gondwanaland also broke up into separate continental masses: South American, African, Indian, Australian and Antarctic. In the Mesozoic, perhaps all modern oceans were formed, except, apparently, the more ancient Pacific Ocean.

In the Late Cretaceous era, a powerful phase of Mesozoic folding appeared in areas adjacent to the Pacific Ocean. Less intense mountain-building movements at this time occurred in a number of areas of the Mediterranean region (Eastern Alps, Carpathians, Transcaucasia). As in the Jurassic period, folding was accompanied by intense magmatism.

Mesozoic rocks are “pierced” by granite intrusions embedded in them. And on the vast expanses of the Siberian, Indian, African-Arabian platforms at the end of the Mesozoic there were enormous outpourings of basaltic lavas that formed trap covers (Swedish ʼʼ trapʼʼ - ladder). Now they come to the surface, for example, along the banks of the Lower Tunguska River. Here you can observe the remains of solid basalts, rising several hundred meters high, which were previously embedded in sedimentary rocks, destroyed after reaching the surface by the processes of weathering and erosion. Vertical ledges of black (dark gray) traps, called “pillars,” alternate with horizontal platforms. This is why climbers and tourists fell in love with them. The thickness of such covers on the Deccan Plateau in Hindustan reaches 2000-3000 m.

ORGANIC WORLD M is ozoic. At the turn of the Paleozoic and Mesozoic eras, the flora and fauna were significantly renewed (Fig. 14, 15). The Triassic period is characterized by the appearance in the seas of new cephalopods (ammonnites, belogemnites) and elasmobranch mollusks, six-rayed corals and other groups of animals. Bony fish appeared.

On land it was a time of reptile dominance. New groups of them arose - the first lizards, turtles, crocodiles, snakes. At the beginning of the Mesozoic, the first mammals appeared - small marsupials the size of a modern rat.

In the Triassic - Jurassic, belemnites, giant herbivorous and predatory reptile lizards - dinosaurs (Greek "dinos" - terrible, "savros" - lizard) appeared and flourished. They reached a length of 30 m or more and weighed up to 60 tons. Dinosaurs (Fig. 16) mastered not only land, but also the sea. Ichthyosaurs lived here (Greek “ichthys” - fish) - large predatory fish lizards that reached a length of more than 10 m and resembled modern dolphins. At the same time, the first flying lizards appeared - pterosaurs (Greek "pteron" - wing), "savros" - lizard). These were mostly small (up to half a meter) reptiles adapted to flight.

Common representatives of pterosaurs were flying lizards - rhamphorhynchus (Greek rhamphos - beak, rhinos - nose) and pterodactyls (Greek pteron - feather, dactylos - finger). Their forelimbs turned into flying organs - membranous wings The main food of rhamphorhynchus were fish and insects.The smallest pterodactyls were the size of a sparrow, the largest reached the size of a hawk.

Flying lizards were not the ancestors of birds. Οʜᴎ represent a special, independent evolutionary branch of reptiles, which completely died out at the end of the Cretaceous period. Birds evolved from other reptiles.

The very first bird, apparently, is Archeopteryx (Greek “archeos” - ancient, “pteron” - wing). It was a transitional form from reptiles to birds. Archeopteryx was the size of a crow. It had short wings, sharp carnassial teeth and a long tail with fan-shaped plumage. The body shape, structure of the limbs and the presence of plumage were similar to birds. But in a number of ways it was still close to reptiles.

Remains of primitive mammals were discovered in Jurassic deposits.

The Cretaceous period is the time of greatest flowering of reptiles. Dinosaurs reached enormous sizes (up to 30 m in length); their mass exceeded 50 tons. They widely populated land and waters and reigned in the air. Flying lizards in Cretaceous period reached gigantic sizes - with a wingspan of about 8 m.

Gigantic sizes were characteristic of some other groups of animals in the Mesozoic. Thus, in the Cretaceous seas there were mollusks - ammonites, whose shells reached a diameter of 3 m.

Of the plants on land, starting from the Triassic period, gymnosperms predominated: conifers, gingkovae, etc.; of the spore plants - ferns. During the Jurassic period, terrestrial vegetation developed rapidly. At the end of the Cretaceous period, angiosperms appeared; grass cover formed on the land.

At the end of the Cretaceous period, the organic world again underwent dramatic changes. Many invertebrates and most giant lizards became extinct. The reasons for their extinction have not been reliably established. According to one hypothesis, the death of dinosaurs is associated with a geological catastrophe that occurred about 65 million years ago. It is believed that a large meteorite collided with the Earth at that time.

In the 70s of the twentieth century. University of California geologist Walter Alvarez and

his father, physicist Luis Alvarez, discovered an unusually high content of iridium, an element found in large quantities in meteorites, in the Cretaceous-Paleogene boundary deposits of the Gubbio section (Italy). Anomalous iridium content was also discovered at the Cretaceous-Paleogene boundary in other

areas of the globe. In this regard, father and son Alvarez put forward a hypothesis about the collision of a large cosmic body of asteroid size with the Earth. The consequence of the collision was the mass extinction of Mesozoic plants and animals, in particular dinosaurs. This happened about 65 million years ago at the turn of the Mesozoic and Cenozoic eras.
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At the moment of the collision, myriads of meteorite particles and terrestrial matter rose into the sky in a giant cloud and obscured the Sun for years. The earth plunged into darkness and cold.

In the first half of the 80s, numerous geochemical studies were carried out. They showed that the iridium content in the Cretaceous-Paleogene boundary deposits is indeed very high - two to three orders of magnitude higher than its average content (clarke) in the earth's crust.

At the end of the Late Period, large groups of higher plants also disappeared.

USEFUL AND RESOURCED MEZOZONES.

Mesozoic sediments contain many minerals. Deposits of ore minerals were formed as a result of basaltic magmatism.

The widespread Triassic weathering crust contains deposits of kaolin and bauxite (Ural, Kazakhstan). During the Jurassic and Cretaceous periods, powerful coal accumulation occurred. In Russia, deposits of Mesozoic brown coals are located within the Lena, South Yakut, Kansk-Achinsk, Cheremkhovo, Chulym-Yenisei, Chelyabinsk basins, in the Far East and in other areas.

The famous oil and gas fields of the Middle East, Western Siberia, as well as Mangyshlak, Eastern Turkmenistan and Western Uzbekistan are confined to Jurassic and Cretaceous deposits.

During the Jurassic period, oil shale (Volga region and General Syrt), sedimentary iron ores (Tula and Lipetsk regions), phosphorites (Chuvashia, Moscow region, General Syrt, Kirov region) were formed.

Phosphorite deposits are confined to the Cretaceous deposits (Kursk, Bryansk, Kaluga, etc.
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region) and bauxite (Hungary, Yugoslavia, Italy, France). Deposits of polymetallic ores (gold, silver, copper, lead, zinc, tin, molybdenum, tungsten, etc.) are associated with chalk granite intrusions and basaltic outpourings. This is, for example, the Sadonskoye (North Caucasus) deposit of polymetallic ores, tin ores Bolivia, etc. Along the shores of the Pacific Ocean stretch two of the richest Mesozoic ore belts: from Chukotka to Indochina and from Alaska to Central America. In South Africa and Eastern Siberia, diamond deposits are confined to Cretaceous deposits.

Cenozoic era. The Cenozoic era lasts 65 million years. On the international geological time scale, it is divided into “Tertiary” and “Quaternary” periods. In Russia and other states of the former Soviet Union, the Cenozoic is divided into three periods: Paleogene, Neogene and Anthropogenic (Quaternary).

The Paleogene period (40.4 million years) is divided into early - Paleocene (10.1 million years), middle - Eocene (16.9 million years) and late - Oligocene (13.4 million years) era. In the Northern Hemisphere in the Paleogene there existed the North American and Eurasian continents. They were separated by the Atlantic Ocean. In the Southern Hemisphere, continents continued to develop independently, breaking away from Gondwana and separated by the depressions of the Atlantic and Indian Oceans.

In the Eocene era, the first phase of powerful Alpine folding appeared in the Mediterranean region. It caused the uplift of some central sections of this area. By the end of the Paleogene, the sea completely left the territory of the Himalayan-Indian part of Tethys.

The formation of numerous deep faults in the North Channel and adjacent areas of Ireland, Scotland, Northern England and the Hebrides; the region of Southern Sweden and the Skagerrak, as well as throughout the entire North Atlantic region (Spitsbergen, Iceland, Western Greenland) contributed to basaltic outpourings.

At the end of the Paleogene period, discontinuous and block movements of the earth's crust became widespread in many parts of the globe. In a number of areas of the Western European Hercynides, a graben system arose (Upper Rhine, Lower Rhine). A system of narrow meridionally elongated grabens (Dead and Red Seas, Lakes Alberta, Nyasa, Tanganyika) arose in the eastern part of the African Platform). It stretches from the northern edge of the platform almost to the extreme south at a distance of over 5000 km. Fault dislocations here were accompanied by enormous outpourings of basaltic magmas.

The Neogene period includes two eras: early - Miocene (19.5 million years) and late - Pliocene (3.5 million years). It is worth saying that the Neogene was characterized by active mountain formation. By the end of the Neogene, Alpine folding transformed most the Tethys region into the youngest alpine folded region in the structure of the earth's crust. At this time, many mountain structures acquired their modern appearance. Chains of the Sunda, Moluccas, New Guinea, New Zealand, Philippine, Ryukkyu, Japanese, Kuril, Aleutian islands and others arose.
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Within the East Pacific coastal margins, coastal ridges rose in a narrow strip. Mountain formation also occurred in the region of the Central Asian mountain belt.

Powerful block movements caused the subsidence of large sections of the earth's crust in the Neogene - areas of the Mediterranean, Adriatic, Black, East China, South China, Japan, Okhotsk and other marginal seas, as well as the Caspian Sea.

The rise and fall of crustal blocks in the Neogene were accompanied by

the origin of deep faults. Lava flowed through them. Eg,

in the Central Plateau region of France. In the zone of these faults, the volcanoes Vesuvius, Etna, as well as the Kamchatka, Kuril, Japanese and Javan volcanoes arose in the Neogene.

In the history of the Earth, there have been frequent periods of cooling, alternating with warming. About 25 million years ago, from the end of the Paleogene, a cooling event occurred. One of the warmings took place at the beginning of the Late Neogene (Pliocene era). The next cold snap formed mountain-valley and sheet glaciers in the northern hemisphere and a thick ice sheet in the Arctic. Long-term freezing of rocks in northern Russia continues to this day.

The Anthropogenic period got its name because at the beginning of this period man appeared (Greek . "anthropos" - man). Its former name is quaternary system. The question of the duration of the Anthropocene period has not yet been finally resolved. Some geologists estimate the duration of the Anthropocene to be at least 2 million years. Anthropocene is divided into Eopleistocene(Greek "Eos" - dawn, "pleistos" - greatest, "kainos" - new), Pleistocene And Holocene(Greek "voice" - all, "kainos" - new). The duration of the Holocene does not exceed 10 thousand years. But some scientists classify the Eopleistocene as the Neogene and place the lower boundary of the Anthropocene at 750 thousand years ago.

At this time, the uplift of the Central Asian mountain fold belt continued more actively. According to some scientists, the mountains of the Tien Shan and Altai rose several kilometers during the Anthropocene period. And the depression of Lake Baikal sank to 1600 m.

Intense volcanic activity manifests itself in the Anthropocene. The most powerful basaltic outpourings in modern times have been observed at mid-ocean ridges and other vast areas of the ocean floor.

“Great” glaciations occurred over vast areas of the northern continents during the Anthropocene period. They also formed the Antarctica ice sheet. The Eopleistocene and Pleistocene are characterized by a general cooling of the Earth's climate and the periodic occurrence of continental glaciations in mid-latitudes. In the Middle Pleistocene, powerful glacial tongues descended to almost 50° N. latitude. in Europe and up to 40° N. in USA. Here the thickness of moraine deposits is a few tens of meters. Interglacial eras were characterized by a relatively mild climate. Average temperatures increased by 6 - 12° C (N.V. Koronovsky, A.F. Yakushova, 1991). .

Formed by the waters of the seas and oceans, huge masses of ice in the form of glaciers advanced onto land. Frozen rocks spread over vast areas. Holocene - post-glacial era. Its beginning coincides with the end of the last continental glaciation of Northern Europe.

ORGANIC WORLD ZOOS. By the beginning of the Cenozoic era, belemnites, ammonites, giant reptiles, etc. died out.
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In the Cenozoic, protozoa (foraminifera), mammals and bony fish began to actively develop. They took a dominant position among other representatives of the animal world. In the Paleogene, oviparous and marsupials predominated among them (a similar fauna of this type was partially preserved in Australia). In the Neogene, these groups of animals receded into the background and the main role began to be played by ungulates, proboscis, predators, rodents and other currently known classes of higher mammals.

Organic world Anthropocene is similar to modern. During the Anthropocene period, humans evolved from primates that existed in the Neogene 20 million years ago.

The Cenozoic era is characterized by a wide distribution of terrestrial vegetation: angiosperms, grasses close to modern ones.

USEFUL AND FOUNDATIONS. During the Paleogene period, powerful coal formation occurred. Brown coal deposits are known in the Paleogene of the Caucasus, Kamchatka, Sakhalin, USA, South America, Africa, India, Indochina, Sumatra. Paleogne manganese ores have been identified in Ukraine (Nikopol), Georgia (Chiatura), the North Caucasus, and Mangyshlak. Paleogene deposits of bauxite (Chulymo-Yenisei, Akmola), oil and gas are known.

Oil and gas deposits are confined to Neogene deposits (Baku, Maykop, Grozny, Southwestern Turkmenistan, Western Ukraine, Sakhalin). In the Black Sea basin, on the territory of the Kerch and Taman Peninsulas, during the Neogene period, precipitation of iron ores occurred in various areas.

During the Anthropogen period, deposits of salts, building materials (crushed stone, gravel, sand, clay, loam), lake-marsh iron ores were formed; as well as placer deposits of gold, platinum, diamonds, tin, tungsten ores, precious stones and etc.

Table 5

Mesozoic era. - concept and types. Classification and features of the category "Mesozoic era." 2017, 2018.

The history of the Earth goes back four and a half billion years. This huge period of time is divided into four eons, which in turn are divided into eras and periods. The final fourth eon - Phanerozoic - includes three eras:

• Paleozoic;
• Mesozoic;
• Cenozoic

significant for the appearance of dinosaurs, the emergence of the modern biosphere and significant geographical changes.

Periods of the Mesozoic era

Ending Paleozoic era marked by the extinction of animals. Development of life in Mesozoic era characterized by the emergence of new species of creatures. First of all, these are dinosaurs, as well as the first mammals.

The Mesozoic lasted one hundred eighty-six million years and consisted of three periods, such as:

• Triassic;
• Jurassic;
• chalky.

The Mesozoic period is also characterized as the era of global warming. There have also been significant changes in the tectonics of the Earth. It was at that time that the only existing supercontinent broke into two parts, which were subsequently divided into the continents that exist in the modern world.

Triassic

The Triassic period is the first stage of the Mesozoic era. The Triassic lasted for thirty-five million years. After the catastrophe that occurred at the end of the Paleozoic on Earth, conditions are observed that are little conducive to the flourishing of life. A tectonic fault occurs and active volcanoes and mountain peaks are formed.

The climate becomes warm and dry, as a result of which deserts form on the planet, and the level of salt in water bodies increases sharply. However, it is precisely at this unfavorable time that mammals and birds appear. This was largely facilitated by the absence of clearly defined climatic zones and the maintenance of uniform temperatures throughout the globe.

Fauna of the Triassic

The Triassic period of the Mesozoic is characterized by significant evolution of the animal world. It was during the Triassic period that those organisms arose that subsequently shaped the appearance of the modern biosphere.

Cynodonts appeared - a group of lizards that were the ancestors of the first mammals. These lizards were covered with hair and had highly developed jaws, which helped them feed on raw meat. Cynodonts laid eggs, but females fed their young with milk. The ancestors of dinosaurs, pterosaurs and modern crocodiles - archosaurs - also arose in the Triassic.

Due to the dry climate, many organisms have changed their habitat to aquatic habitats. This is how new species of ammonites, mollusks, as well as bony and ray-finned fish appeared. But the main inhabitants of the deep sea were predatory ichthyosaurs, which, as they evolved, began to reach gigantic sizes.

Towards the end of the Triassic natural selection did not allow all the animals that appeared to survive; many species could not withstand competition with others, stronger and faster. Thus, by the end of the period, thecodonts, the ancestors of dinosaurs, predominated on land.

Plants during the Triassic period

The flora of the first half of the Triassic did not differ significantly from the plants of the end of the Paleozoic era. Various types of algae grew in abundance in the water, seed ferns and ancient conifers were widespread on land, and lycophytes were widespread in coastal zones.

By the end of the Triassic, the land was covered with a cover of herbaceous plants, which greatly contributed to the appearance of a variety of insects. Plants of the mesophytic group also appeared. Some cycad plants have survived to this day. It grows in the Malay Archipelago zone. Most plant species grew on the planet's coastal areas, while conifers predominated on land.

Jurassic period

This period is the most famous in the history of the Mesozoic era. The Jura is the European mountains that give its name to this time. Sedimentary deposits from that era have been found in these mountains. The Jurassic period lasted fifty-five million years. It acquired geographical significance due to the formation of modern continents (America, Africa, Australia, Antarctica).

The separation of the two previously existing continents of Laurasia and Gondwana served to form new bays and seas and raise the level of the world's oceans. This had a beneficial effect on making it more humid. The air temperature on the planet dropped and began to correspond to a temperate and subtropical climate. Such climate change contributed greatly to the development and improvement of flora and fauna.

Animals and plants of the Jurassic period

The Jurassic period is the era of dinosaurs. Although other forms of life also evolved and took on new forms and species. The seas of that period were filled with many invertebrates, the structure of whose bodies was more developed than in the Triassic. Bivalve mollusks and intrashell belemnites, the length of which reached three meters, became widespread.

The insect world has also received evolutionary growth. The appearance of flowering plants also provoked the appearance of pollinating insects. New species of cicadas, beetles, dragonflies and other terrestrial insects have emerged.

Climatic changes that occurred during the Jurassic period resulted in heavy rainfall. This, in turn, gave impetus to the spread of lush vegetation across the surface of the planet. In the northern belt of the earth, herbaceous ferns and ginkgo plants predominated. The southern zone consisted of tree ferns and cycads. In addition, the Earth was filled with various coniferous, cordaite and cycad plants.

Age of Dinosaurs

During the Jurassic period of the Mesozoic, reptiles reached their evolutionary peak, ushering in the era of dinosaurs. The seas were dominated everywhere by giant dolphin-like ichthyosaurs and plesiosaurs. If ichthyosaurs were inhabitants of an exclusively aquatic environment, then plesiosaurs from time to time needed access to land.

Dinosaurs living on land amazed us with their diversity. Their sizes varied from 10 centimeters to thirty meters, and they weighed up to fifty tons. Herbivores predominated among them, but there were also ferocious predators. A huge number of predatory animals provoked the formation of certain elements of defense in herbivores: sharp plates, spines and others.

The airspace of the Jurassic period was filled with dinosaurs that could fly. Although they needed to climb to higher ground to fly. Pterodactyls and other pterosaurs swarmed and swooped above the surface of the earth in search of food.

Cretaceous period

When choosing the name for the next period, the main role was played by writing chalk, formed in the deposits of dying invertebrate organisms. The period called the Cretaceous was the final one Mesozoic era. This time lasted eighty million years.

The newly formed continents move, and the tectonics of the Earth increasingly takes on a familiar appearance. to modern man. The climate became noticeably colder, and at this time the ice caps of the north and south poles formed. The planet is also divided into climatic zones. But in general, the climate remained quite warm, helped by the greenhouse effect.

Cretaceous biosphere

Belemnites and mollusks continue to evolve and spread in water bodies, and sea urchins and the first crustaceans also develop.

In addition, fish with hard bones actively develop in reservoirs. Insects and worms have progressed greatly. On land, the number of vertebrates increased, among which the leading positions were occupied by reptiles. They actively consumed vegetation earth's surface and destroyed each other. During the Cretaceous period, the first snakes arose that lived both in water and on land. Birds, which began to appear at the end of the Jurassic period, became widespread and actively developed during the Cretaceous period.

Among vegetation, flowering plants have received the greatest development. Spore-bearing plants died out due to their reproductive characteristics, giving way to more progressive ones. At the end of this period, gymnosperms evolved noticeably and began to be replaced by angiosperms.

The end of the Mesozoic era

The history of the Earth includes two events that contributed to the mass extinction of the planet's fauna. The first, the Permian catastrophe, marked the beginning of the Mesozoic era, and the second marked its end. Most animal species that actively evolved in the Mesozoic became extinct. Ammonites, belemnites, and bivalves ceased to exist in the aquatic environment. Dinosaurs and many other reptiles disappeared. Many species of birds and insects also disappeared.

To date, there is no proven hypothesis about what exactly was the impetus for the mass extinction of fauna in the Cretaceous period. There are versions about the negative impact greenhouse effect or about radiation caused by a powerful cosmic explosion. But most scientists are inclined to believe that the cause of the extinction was the fall of a gigantic asteroid, which, when it hit the surface of the Earth, lifted a mass of substances into the atmosphere, covering the planet from sunlight.

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Mesozoic era(248-65 million years ago) - the fourth era in the evolutionary process of life on 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 erathema of the Mesozoic era lasts 35 million years. This is the time of formation of the Atlantic Ocean. The single continent of Pangea again begins to break into two parts - Gondwana and Laurasia. Inland continental reservoirs are beginning to actively dry up. The depressions left from them are gradually filled with rock deposits. New mountain heights and volcanoes are appearing and exhibiting increased activity. A huge part of the landmass is still occupied by desert zones with weather conditions, unsuitable for the life of most species of living beings. The salt level in water bodies is rising. During this time period, representatives of birds, mammals and dinosaurs appear on the planet.

Jurassic period (Jura)- the most famous period of the Mesozoic era. It received its name due to the sedimentary deposits of that time found in the Jura (mountain ranges 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 located in the order to which we are accustomed. Deep bays and small seas appear, separating the continents. Active formation of mountain ranges continues. The Arctic Sea floods the north of Laurasia. As a result, the climate is moistened, and vegetation forms in place of deserts.

Cretaceous period (Cretaceous). The final period of the Mesozoic era occupies a time period of 79 million years. Angiosperms appear. As a result of this, the evolution of fauna representatives begins. The movement of continents continues - Africa, America, India and Australia are moving away from each other. The continents of Laurasia and Gondwana begin to break up into continental blocks. Huge islands are forming in the south of the planet. Expanding Atlantic Ocean. The Cretaceous period is the heyday of flora and fauna on land. Due to the evolution of the plant world, fewer minerals enter the seas and oceans. The amount of algae and bacteria in water bodies decreases.

In details periods of the Mesozoic era will be discussed in the following lectures.

Climate of the Mesozoic era

Climate of the Mesozoic era at the very beginning there was one on the entire planet. The air temperature at the equator and poles remained at the same level. At the end of the first period of the Mesozoic era, drought reigned on Earth for most of the year, which was briefly replaced by rainy seasons. But, despite the arid conditions, the climate became significantly colder than it was during the Paleozoic period. Some species of reptiles have fully adapted to cold weather. From these species of animals mammals and birds would later develop.

During the Cretaceous period it becomes 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 lycophytes, various ferns, the ancestors of modern palms, conifers and ginkgo trees. In the seas and oceans, the dominance belonged to algae that formed reefs.

The increased humidity of the climate of the Jurassic period led to the rapid formation of plant matter on the planet. The forests consisted of ferns, conifers and cycads. Thujas and araucarias grew near the ponds. In the middle of the Mesozoic era, two vegetation belts formed:

1. Northern, which was dominated by herbaceous ferns and gingkovic trees;
2. Southern. Tree ferns and cycads reigned here.

In the modern world, ferns, cycads (palm trees reaching 18 meters in size) and cordaites of that time can be found in tropical and subtropical forests. Horsetails, mosses, cypresses and spruce trees had practically no 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 were able to quickly spread throughout the planet. Also at this time, ginkgo trees with leaves that fall off during the cold season begin to grow. Conifers forested areas of this time period are very similar to modern ones. These include yews, firs and cypresses.

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

Angiosperms appeared in the Cretaceous period. From this moment a new stage in the development of plant life begins. Angiosperms (flowering plants) are at the top rung of the evolutionary ladder. They have special reproductive organs - stamens and pistil, which are located in the flower cup. Their seeds, unlike gymnosperms, are hidden by a dense protective shell. These plants of the Mesozoic era quickly adapt to any climatic conditions and actively develop. Behind short term Angiosperms began to dominate the entire Earth. Their various types and forms have reached the modern world - eucalyptus, magnolia, quince, oleander, walnut trees, oak, birch, willow and beech. Of the gymnosperms of the Mesozoic era, we are now familiar only with coniferous species - fir, pine, sequoia and some others. The evolution of plant life of that period significantly outstripped 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 formed, which gradually replaced the ancient species.

One of these types of reptiles was the animal-like pelycosaurs - sailing lizards. On their backs there was a huge sail, like a fan. They were replaced by therapsids, which were divided into 2 groups - predators and herbivores. Their legs were powerful and their tails were short. Therapsids were much superior to pelycosaurs in speed and endurance, 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 evolve are the cynodonts (dog teeth). These animals got their name due to their powerful jaw bones and sharp teeth, with which they could easily chew raw meat. Their bodies were covered with thick hair. The females laid eggs, but the newborn cubs fed on their mother's milk.

At the beginning of the Mesozoic era it was formed the new kind lizards - 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 bodies of water. Most thecodonts walked on 4 legs. But there were also individuals that ran on their hind legs. In this way, these animals developed incredible speed. After some time, thecodonts evolved into dinosaurs.

By the end of the Triassic period, 2 species of reptiles predominated. Some are the ancestors of the crocodiles of our time. Others turned into dinosaurs.

Dinosaurs have a body structure that is not similar to other lizards. Their paws are located under the body. This feature allowed 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 coelophysis, powerful herrerasaurs and huge plateosaurs.

Besides dinosaurs, archosaurs gave rise to another species of reptile that was different from the rest. These are pterosaurs - the first lizards that can fly. They lived near bodies of water and ate various insects for food.

The fauna of the deep sea of ​​the Mesozoic era is also characterized by a variety of species - ammonites, bivalves, families of sharks, bony and ray-finned fish. The most prominent 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 nothosaurs had sharp fangs. Placadonts, similar to modern newts, were searched for seabed shells of mollusks that were bitten with teeth. Tanystrophei lived on land. Long (2-3 times the body size), slender necks allowed them to catch fish while standing on the shore.

1 more group sea ​​lizards Triassic period - plesiosaurs. At the beginning of the era, plesiosaurs reached a size of only 2 meters, and by the middle of the Mesozoic they evolved into giants.

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

Archeopteryx is the first creature standing on the border between lizards and birds. Archeopteryx did not yet know how to fly long distances. The beak was replaced by jaws with sharp teeth. The wings ended in fingers. Archeopteryx was the size of a modern crow. They lived mainly in forests and ate insects and various seeds.

In the middle of the Mesozoic era, pterosaurs were divided into 2 groups - pterodactyls and rhamphorhynchus. Pterodactyls lacked a tail and feathers. But there were large wings and a narrow skull with few teeth. These creatures lived in flocks on the coast. During the day they obtained food for themselves, and at night they hid in the trees. Pterodactyls ate fish, shellfish and insects. This group of pterosaurs had to jump from high places to take to the skies. Rhamphorhynchus also lived on the coast. They ate fish and insects. They had long tails with a blade at the end, narrow wings and a massive skull with teeth. 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 are developing and bony fish. New species of plesiosaurs and ichthyosaurs, sea turtles and crocodiles appeared. Saltwater crocodiles developed flippers instead of legs. This feature allowed them to increase speed in the aquatic environment.

During the Cretaceous period of the Mesozoic era Bees and butterflies appeared. Insects carried pollen, and flowers gave them food. This is how it began long-term cooperation insects and plants.

The most famous dinosaurs of the time were the predatory tyrannosaurs and tarbosaurs, the herbivorous bipedal iguanodons, the four-legged rhinoceros-like Triceratops and the small armored ankylosaurs.

Most mammals of that period belong to the subclass Allotheria. These are small animals, similar to mice, weighing no more than 0.5 kg. The only exceptional species is the repenomama. They grew up to 1 meter and weighed 14 kg. At the end of the Mesozoic era, the evolution of mammals occurs - the ancestors of modern animals separate from allotheria. They are divided into 3 species - oviparous, marsupial and placental. It is they who replace the dinosaurs at the beginning of the next era. Rodents and primates emerged from the placental species of mammals. Purgatorius became the first primates. From marsupial species modern opossums evolved, and egg-laying ones gave rise to platypuses.

The airspace is dominated by early pterodactyls and new species of flying reptiles - Orcheopteryx and Quetzatcoatli. 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. Many ancestors appeared during the Cretaceous period modern birds- ducks, geese, loons. The length of the birds was 4-150 cm, weight - from 20 grams. up to several kilograms.

The seas were dominated by huge predators reaching 20 meters in length - ichthyosaurs, plesiosaurs and mososaurs. Plesiosaurs had a very long neck and a small head. Their large size did not allow them to develop higher 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 unchanged. The turtles of this time period were also no different from those we see now. Their weight reached 2 tons, length - from 20 cm to 4 meters.

By the end of the Cretaceous period, most reptiles began to die out en masse.

Minerals of the Mesozoic era

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

In Asia, due to 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 the Paleozoic era, but even during this period several large deposits of brown and hard coal were formed - the Kansky basin, Bureinsky, Lensky.

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

Mesozoic era

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

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

Triassic

The Triassic period gets its name from the fact that its sediments include three different complex rocks: lower - continental sandstone, middle - limestone and upper - Naper.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Mastodonosaurus.

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

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

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

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

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

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

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

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

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

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

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

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

The Triassic period lasted 35 million years.

Jurassic period

For the first time, deposits of this period were found in the Jura (mountains in Switzerland and France), hence the name of the period. The Jurassic period is divided into three divisions: Leyas, Doger and Malm.

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

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

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

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

The climate of the Jurassic period depended not only on sunlight. Many volcanoes and magma outpourings onto the bottom of the oceans heated the water and atmosphere, saturating the air with water vapor, which then rained onto the land and flowed into lakes and oceans in stormy streams. This is evidenced by numerous freshwater deposits: white sandstones alternating with dark loams.

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

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

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

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

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

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

Brachiosaurus.

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

Diplodocus.

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

Brontosaurus.

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

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

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

Pterodactyl.

Pterodactyls in most cases were tailless, varying in size - from the size of a sparrow to a crow. They had wide wings and a narrow skull elongated forward with a small number of teeth in the front. Pterodactyls lived in large flocks on the shores of the lagoons of the Late Jurassic Sea. During the day they hunted, and at nightfall they hid in trees or rocks. The skin of pterodactyls was wrinkled and bare. They ate mainly fish, sometimes sea lilies, mollusks, and insects. In order to fly, pterodactyls were forced to jump from cliffs or trees.

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

Rhamphorhynchus.

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

It should be noted that flying lizards were not the ancestors of birds and bats. Flying lizards, birds and bats each originated and developed in their own way, and there are no close family ties between them. The only one common feature for them - the ability to fly. And although they all acquired this ability due to changes in the forelimbs, the differences in the structure of their wings convince us that they had completely different ancestors.

The seas of the Jurassic period were inhabited by dolphin-like reptiles - ichthyosaurs. They had a long head, sharp teeth, large eyes surrounded by a bony ring. The length of the skull of some of them was 3 m, and the length of the body was 12 m. The limbs of ichthyosaurs consisted of bone plates. The elbow, metatarsus, hand and fingers differed little from each other in shape. About a hundred bone plates supported the wide flipper. The shoulder and pelvic girdles were poorly developed. There were several fins on the body. Ichthyosaurs were viviparous animals. Plesiosaurs lived alongside ichthyosaurs. They had a thick body with four flipper-like limbs, a long snake-like neck with a small head.

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

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

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

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

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

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

The sea urchins that settled on the reefs are undergoing significant changes. Along with the round forms that have survived to this day, there lived bilaterally symmetrical irregular shape hedgehogs Their body was stretched in one direction. Some of them had a jaw apparatus.

The Jurassic seas were relatively shallow. Rivers brought muddy water into them, delaying gas exchange. The deep bays were filled with rotting debris and silt containing large amounts of hydrogen sulfide. That is why in such places the remains of animals carried by sea currents or waves are well preserved.

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

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

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

Archeopteryx.

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

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

This period lasted 55 million years.

Cretaceous period

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

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

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

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

The climate has changed. In the high latitudes in the north during the Cretaceous period there was already 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 in general was much warmer than today. Ferns, cycads, ginkgos, bennetites, and conifers, in particular sequoias, yews, pines, cypresses, and spruces, were still common.

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

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

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

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

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

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

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

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

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

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

The disappearance of ammonites also contributed to sudden change physical and geographical conditions in the Cretaceous period.

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

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

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

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

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

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

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

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

Triceratops.

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

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

Tyrannosaur.

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

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

Scolosaurus.

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

Pteranodon.

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

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

Hesperornis.

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

Ichthyornis.

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

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

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

The birds that had constant temperature bodies and were covered with feathers. They incubated eggs and fed chicks.

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

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

The Cretaceous period lasted 70 million years.

From the book Journey to the Past author Golosnitsky Lev Petrovich

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

From the book Before and After Dinosaurs author Zhuravlev Andrey Yurievich

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

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

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

Kaytsukov A.A. 1

Konstantinova M.V. 1 Boeva ​​E.A. 1

1 Municipal budgetary educational institution secondary school 5, Odintsovo

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INTRODUCTION

The world around us is very rich and diverse. We are surrounded by objects of living and inanimate nature. Nature is a beautiful, mysterious, and sometimes little-studied and unknown world. The history of dinosaurs is very interesting, since it represents a huge era in the life of our planet, in comparison with which human history looks like a moment. But no one can say exactly 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 completely disappeared from the face of the Earth. You can only speculate and study, study, study. One such little-studied page of living nature includes information about dinosaurs - animals that lived on our planet long before the appearance of humans.

From a very early age I liked watching programs about dinosaurs.

My parents started buying me books, the first thing I did was look for pages that talked about dinosaurs, I looked at drawings with dinosaurs, I was interested in what they looked like, I loved drawing them. When I learned to read, I wanted to understand how they lived, what they looked like, why they became extinct, and whether they had relatives in our world. After all, many modern animals are similar to 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 and what did they eat?

Why did dinosaurs become extinct?

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

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 it. Dinosaurs - who are they?

Tasks:

1. 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, which was replaced by the Paleogene period of the Cenozoic era.

Hypothesis: The cause of the death of dinosaurs. The extinction of dinosaurs as a result of sudden climate change on our planet.

Chapter 1. Mesozoic era. Age of dinosaurs.

For many years people thought that the world in which they live was created in the state in which it appears now. And the age of the Earth was considered to be several thousand years. But relatively recently it was proven that the age of our planet exceeds 6 billion years, and, accordingly, life originated a very, very long time ago. It arose through chance, through 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 into the abyss of time.

Triassic

The first of three periods of the Mesozoic era. The Triassic period in Earth's history marked the beginning of the Mesozoic era. The Triassic period is a time when the remains of the animal world preserved from the Permian period were replaced by new, revolutionary species of animals. 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 went extinct along with the dinosaurs.

Tectonics of the Triassic period:

Back to top Triassic period There was a single continent on Earth - Pangea. During Triassic period, Pangea split into two continents: Laurasia in the northern part and Gondwana in the southern part. A large bay that began in the east of Gondwana extended all the way to the northern coast of modern Africa, then turned south, almost completely separating Africa from Gondwana. A long bay stretched from the west, separating the western part of Gondwana from Laurasia. Many depressions appeared on Gondwana, which were gradually filled with continental sediments. The Atlantic Ocean began to form. The continents were connected to each other. The land prevailed over the sea. The level of salinity in the seas has increased. In the middle of the Triassic period, volcanic activity increased. Inland seas dry up and form deep depressions. Along with changes in the distribution of sea and land, new mountain ranges and volcanic areas were formed. IN Triassic period vast territories were covered with deserts with harsh conditions for animal life. Life bubbled only along the banks of reservoirs.

Triassic became a transition period between the Paleozoic and Mesozoic. There was an intensive replacement of some animal and plant forms by others. Only a few families moved from the Paleozoic era to the Mesozoic. 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 first Triassic period the fauna was the same all over the land. Pangea was a single continent and different kinds could spread unhindered throughout the land. However, when studying the deposits of the Triassic period, one can easily verify that there is no sharp line between them and the Permian deposits; therefore, some forms of plants and animals were replaced by others, probably gradually. The main reason was not catastrophes, but the evolutionary process: more perfect forms gradually replaced less perfect ones.

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

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

Gigantic forms of cephalopods developed in the seas. The diameter of the shells of some of them was up to 5 m. True, even now the seas are inhabited by gigantic cephalopods, for example squids, reaching 18 m in length, but in the Mesozoic era there were much more gigantic forms. The Triassic seas were inhabited by calcareous sponges, bryozoans, leaf-footed crayfish, and ostracods. Starting from the Triassic period, reptiles, which moved to live in the sea, gradually populated increasingly vast areas of the ocean.

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

Deposits of oil, natural gases, brown and hard coal, iron and copper ores, and rock salt are associated with deposits of the Triassic period. The composition of the atmosphere of the Triassic period changed little compared to the Permian. The climate became wetter, but deserts remained in the center of the continent. Some plants and animals of the Triassic period have survived to this day in the region of Central Africa and South Asia. This suggests that the composition of the atmosphere and the climate of individual land areas remained almost unchanged during the Mesozoic and Cenozoic eras.

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 divided into three divisions: Leyas, Doger and Malm.

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

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

Intense tectonic movements at the end of the Triassic and the beginning of the Jurassic periods contributed to the deepening of large bays, which gradually separated Africa and Australia from Gondwanaland. The gulf between Africa and America has deepened. Depressions formed in Laurasia: German, Anglo-Paris, West Siberian. The Arctic Sea flooded the northern coast of Laurasia. The lush vegetation of the Jurassic period contributed to the widespread distribution of reptiles. Dinosaurs have evolved significantly. Among them, lizard-hatched and ornithischian are distinguished. Lizards moved on four legs, had five toes on their feet, and ate plants. At this time, huge, the largest land animals that ever existed on Earth appeared: brachiosaurus, apatosaurus, diplodocus, supersaurus, ultrasaurus and seismosaurus. Small gazelles and larger beaked dinosaurs led a group lifestyle. Then came the amazing spiny dinosaurs. Most of them had a long neck, small head and long tail. They had two brains: one small one in the head; the second is much larger in size - at the base of the tail. The largest of the Jurassic dinosaurs was the Brachiosaurus, reaching a length of 26 m and weighing about 50 tons. It had columnar legs, a small head, and a thick long neck. Brachiosaurs lived on the shores of Jurassic lakes and fed on aquatic vegetation. Every day, the brachiosaurus needed at least half a ton of green mass. 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 nibbled grass and swallowed stones. They all found a mate, laid eggs and raised young. Dinosaurs moved in different ways: some on two legs, some on four legs. Many lizards swam, some even tried to fly. They had to fight, escape from pursuers, hide and die. Fossil remains of dinosaurs have been found in literally all parts 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 became extinct. 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 also often called the era of dinosaurs. Although the dinosaurs themselves have long since disappeared from the face of the Earth, the memory of them is reliably preserved by stones. Research has 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 widely spaced legs, 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 arose in the Triassic period. . First typical representatives Dinosaurs of that time were medium-sized bipedal predators.

Soon, larger and increasingly four-legged herbivorous dinosaurs appeared. Finally, at the end of this period, the first small bipedal herbivores arose. The first birds appeared during the Jurassic period. Their ancestors were the ancient reptiles pseudosuchians, which also gave rise to dinosaurs and crocodiles. Ornithosuchia is most similar to birds. She, like a bird, walked on her hind legs, had a strong pelvis and was covered with feather-like scales. Some pseudosuchians moved to live in trees. Their forelimbs were specialized for grasping branches with their fingers. The pseudosuchian skull had lateral depressions, which significantly reduced the mass of the head. Climbing trees and jumping on branches strengthened the hind limbs. Gradually expanding forelimbs supported the animals in the air and allowed them to glide. An example of such a reptile is Scleromochlusa. His long, thin legs indicate that he was a good jumper. Elongated forearms helped animals climb and cling to branches of trees and bushes. The most important moment in the process of transformation of reptiles into birds was the transformation of scales into feathers. The animals' hearts had four chambers, which ensured a constant body temperature. In the Late Jurassic period, the first birds appeared - Archeopteryx, the size of a pigeon. In addition to short feathers, Archeopteryx had seventeen flight feathers on its wings. The tail feathers were located on all tail vertebrae and were directed back and down. Some researchers believe that the bird's feathers were bright, like those of modern tropical birds, others that the feathers were gray or brown, and still others that they were motley. The mass of the bird reached 200 g. Many signs of Archeopteryx indicate its family ties with reptiles: three free fingers on the wings, a head covered with scales, strong conical teeth, a tail consisting of 20 vertebrae. The bird's vertebrae were biconcave, like those of fish. Archeopteryx lived in araucaria and cycad forests. They ate mainly insects and seeds. Predators appeared among mammals. Small in size, they lived in forests and dense bushes, hunting small lizards and other mammals. Some of them have adapted to life in trees.

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

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

1.3.Cretaceous period

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Triceratops had three horns on their heads and a huge bone shield that reliably protected the animals from predators. They lived mainly in dry places. They ate vegetation. Styracosaurs had nasal projections - horns and six horny spines on the posterior edge of the bony shield. Their heads reached two meters in length. The spines and horns made Styracosaurus dangerous to many predators.

The most terrible predatory lizard was the Tyrannosaurus. It reached a length of 14 m. Its skull, more than a meter long, had large sharp teeth. The tyrannosaurus moved on powerful hind legs, supported by a thick tail. Its front legs were small and weak. The tyrannosaurs left fossilized footprints 80 cm long. The tyrannosaurus's step was 4 m. Flying lizards still continued to exist. The huge pteranodon, whose wingspan was 10 m, had a large skull with a long bony crest on the back of its head and a long toothless beak. The animal's body was relatively small. Pteranodons ate fish. Like modern albatrosses, they spent most of their lives in the air. Their colonies were located by the sea. Recently, the remains of another pteranodon were found in the Cretaceous sediments of America. Its wingspan reached 18 m. Birds appeared that could fly well. Archeopteryx became completely extinct. However, some birds had teeth.

In Hesperornis, a waterfowl, the long finger of the hind limbs was connected to three others by a short swimming membrane. All the fingers had claws. All that remained of the forelimbs were slightly bent humerus bones in the form of a thin stick. Hesperornis had 96 teeth. Young teeth grew inside the old ones and replaced them as soon as they fell out. Hesperornis is very similar to the modern loon. It was very difficult for him to move on land. Raising the front part of the body and pushing off the ground with its feet, Hesperornis moved in small jumps. However, he felt free in the water. He dived well, and it was very difficult for fish to avoid his sharp teeth. In the Late Cretaceous period, toothless birds appeared, whose relatives - flamingos - still exist today. There are many hypotheses regarding the reasons for the extinction of dinosaurs. Some researchers believe that the main reason for this was mammals, of which many appeared at the end of the Cretaceous period. Predatory mammals exterminated dinosaurs, and herbivores intercepted plant food from them. A large group of mammals ate dinosaur eggs. According to other researchers, the main reason for the mass death of dinosaurs was a sharp change in physical and geographical conditions at the end of the Cretaceous period. Cold temperatures and droughts led to a sharp decrease in the number of plants on Earth, as a result of which the giant dinosaurs began to feel a lack of food. They were dying. And the predators for whom dinosaurs served as prey also died, since they had nothing to eat. Perhaps the sun's heat was not enough for the embryos to mature in dinosaur eggs. In addition, cold temperatures also had a detrimental effect on adult dinosaurs. Not having a constant body temperature, they depended on the temperature of the environment. Like modern lizards and snakes, they were active in warm weather, but moved sluggishly in cold weather, could fall into winter torpor and became easy prey for predators. Dinosaurs' skin did not protect them from the cold. And they hardly cared about their offspring. Their parental functions were limited to laying eggs. Unlike dinosaurs, mammals had a constant body temperature, and therefore suffered less from cold snaps. In addition, they were protected by wool. And most importantly, they fed their cubs with milk and took care of them. Thus, mammals had certain advantages over dinosaurs. Birds that had a constant body temperature and were covered with feathers also survived. They incubated eggs and fed chicks.

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

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

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

Chapter 2. Causes of the death of dinosaurs. According to paleontologists, dinosaurs went extinct about 65 million years ago.

Scientists put forward various hypotheses about the reasons for 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 covered the Earth from direct sun rays and caused a cooling of the planet.

Increased volcanic activity, which led to the release of large amounts of ash into the atmosphere, which covered the Earth from direct sunlight, causing a sharp cooling.

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

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

Widespread epidemic among dinosaurs.

The emergence of flowering plants - dinosaurs were unable to adapt to the change in vegetation type.

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

The dinosaurs were destroyed by some planetary upheaval.

Dinosaurs simply “didn’t keep up” with the usual but steady change in the Earth’s biosphere.

In modern paleontology, the biosphere version of the extinction of dinosaurs dominates - this is the appearance of flowering plants and gradual climate change. At the same time, insects feeding on flowering plants appeared, and previously existing insects began to die out.

Animals actively adapted to feeding on green mass. Small mammals appeared whose food was only plants. This led to the emergence of corresponding predators, which also became mammals. Small-sized mammalian predators were harmless to adult dinosaurs, but they fed on their eggs and young, creating difficulties for dinosaurs in reproduction.

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

It can also be assumed that dinosaurs did not become extinct at all, but made evolutionary development. Thus, 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 descendants of not even one, but several branches of dinosaurs.

While excavating, scientists discovered hundreds of different species of dinosaurs. Researchers were able to restore the skeletons of these animals and recreate a picture of their life. Today, in many countries around the world there are museums that display 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, rich in a 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 found skeletons of reptiles.

Conclusion.

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

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

Dinosaurs became extinct as a result of severe climate change.

When we began research on the topic, I had to sort through a large number of books and magazines dedicated to the Mesozoic era - THE ERA OF DINOSAURS. 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, M.: Eksmo, 2007.

2.David Burney, translation from English by I.D. Andrianova, Children's encyclopedia “Prehistoric World”;

3.K. Clark, “These Amazing Dinosaurs and Other Prehistoric Animals,” Swallowtail Publishing, 1998.

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

5.Sheremetyev “Dinosaurs. What? For what? Why?"

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

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

8. Ushakov’s dictionary, page 332

Annex 1.

Mesozoic era. Age of dinosaurs.

Appendix 2.

Triassic

Appendix 3

Jurassic period

Appendix 4

Cretaceous period