What plants were not in the Triassic period. Report: Mesozoic era

Era. It lasted from 50 million years ago to 200 million years ago, that is, for 50-51 million years. In order not to get confused in eons, eras and periods, use the geochronological scale of the history of the Earth, which is located as a visual clue.

Triassic known for several significant events in the history of the formation of the Earth's surface, as well as the history of the development of life on the planet. First of all, it is worth noting the split of the supercontinent Pangea. The supercontinent Pangea was formed back in and is considered the largest continent ever to have existed. In the Triassic period, the supercontinent began to split and diverge. One continent began to divide into many. We see the consequences of this disengagement even today. Since then, the continents have continued to exist separately and will again converge into one single supercontinent only in the distant future.

Life in the Triassic period experienced not the best of times. If at the beginning of the previous period - - life was actively developing, then the mass extinction, which began at the end of the Permian and continued throughout the Triassic, destroyed about 96% of all marine species and 73% of terrestrial vertebrate species. In the Triassic period, the extinction and decline in the species diversity of animals that appeared in previous periods continued, but it was this factor that allowed the emergence of new animal species that replaced the empty niches.

In the Triassic, belemnites, ammonites, snails, and oysters appeared. Also in the Triassic, archosaurs appeared - the ancestors of crocodiles, ichthyosaurs, turtles, bony fish. It is also worth noting that such orders of insects as Diptera, Orthoptera and Hymenoptera first appeared in the Triassic. Although, judging by the overall picture, as a result of extinction, there was a strong drop in the diversity of insects. Among the most notable changes in the animal kingdom that the mass extinction brought with it was the emergence of fast-moving land reptiles (Archosauriformes), which are considered the ancestors of dinosaurs, which became widespread in subsequent periods - the Jurassic and Cretaceous. mass extinction gave impetus to warm-blooded mammals. In the Triassic, the genus of animals Protoavis appeared, which is considered the ancestor of birds.

Animals of the Triassic period

Hypuronector

Desmatosuchus

Mastodonsaurus

Ornithosuchus

Plateosaurus

prestosuchus

Protoavis

Protorosaurus

Scleromochlus

Sclerothorax

Phytosaurus

Shonisaurus

Eodromaeus

Eocursor

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

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

The Triassic period got its name from the fact that three different rock complexes are considered to be its deposits: the lower one is continental sandstone, the middle one is limestone and the upper one is neiper.

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

During the Triassic period, the northern continent of Laurasia joined with the southern one - Gondwana. The great bay, which began in the east of Gondwana, stretched all the way to the northern coast of modern Africa, then turned south, almost completely separating Africa from Gondwana. A long bay stretched from the west, separating the western part of Gondwana from Laurasia. Many depressions arose on Gondwana, gradually filled with continental deposits.

Volcanic activity intensified in the Middle Triassic. The inland seas become shallow, and numerous depressions are formed. The formation of the mountain ranges of South China and Indonesia begins. On the territory of the modern Mediterranean, the climate was warm and humid. It was cooler and wetter in the Pacific zone. Deserts dominated the territory of Gondwana and Laurasia. The climate of the northern half of Laurasia was cold and dry.

Along with changes in the distribution of the sea and land, the formation of new mountain ranges and volcanic regions, the change of some animals and vegetable forms others. Only a few families have moved from Paleozoic era to the Mesozoic. This gave grounds to some researchers to assert about the great catastrophes that occurred at the turn of the Paleozoic and Mesozoic. However, when studying the deposits of the Triassic period, one can easily be convinced that there is no sharp boundary between them and the Permian deposits, therefore, some forms of plants and animals were replaced by others, probably gradually. main reason were not catastrophes, but an evolutionary process: more perfect forms gradually replaced less perfect ones.

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

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

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

The composition of the atmosphere of the Triassic period has changed little compared to the Permian. The climate became more humid, but the deserts in the center of the continent remained. Some plants and animals of the Triassic period have survived to this day in the region of Central Africa and South Asia. This suggests that the composition of the atmosphere and the climate of individual land areas have not changed much during the Mesozoic and Cenozoic eras.

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

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

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

The ginkgos were pretty tall trees, their leaves formed dense crowns. A special place among the Triassic gymnosperms was occupied by bennetites - trees with whorled large complex leaves resembling the leaves of cycads. The reproductive organs of bennetites occupy an intermediate place between the cones of cycads and the flowers of some flowering plants, in particular magnoliaceae. Thus, it is probably the bennetites that should be considered the ancestors of flowering plants.

Of the invertebrates of the Triassic period, all types of animals that exist in our time are already known. The most typical marine invertebrates were reef-building animals and ammonites. In the Paleozoic, animals already existed that covered the bottom of the sea in colonies, forming reefs, although not very powerful. In the Triassic period, when many colonial six-ray corals appear instead of tabulates, the formation of reefs up to a thousand meters thick begins. Cups of six-pointed corals had six or twelve calcareous partitions. As a result of the mass development and rapid growth of corals, underwater forests were formed on the bottom of the sea, in which numerous representatives of other groups of organisms settled. Some of them took part in reef formation. bivalves, algae, sea ​​urchins, sea ​​stars, sponges lived between corals. Destroyed by waves, they formed coarse-grained or fine-grained sand, which filled all the voids of the corals. Washed out by waves from these voids, calcareous silt was deposited in bays and lagoons. Some bivalve mollusks are quite characteristic of the Triassic period. Their paper-thin shells with brittle ribs in some cases form whole layers in the deposits of this period. Bivalve mollusks lived in shallow muddy bays-lagoons, on reefs and between them. In the Upper Triassic period, many thick-shell bivalve mollusks appeared, firmly attached to the limestone deposits of shallow water basins.

At the end of the Triassic, due to increased volcanic activity, part of the limestone deposits was covered with ash and lavas. Steam rising from the depths of the Earth brought with it many compounds from which deposits of non-ferrous metals were formed. The most common of the gastropod molluscs were pronebranchial. Ammonites were widely distributed in the seas of the Triassic period, the shells of which in some places accumulated in huge numbers. Appearing in Silurian period, they did not yet play a big role among other invertebrates throughout the Paleozoic era. Ammonites could not successfully compete with the rather complex nautiloids. Ammonite shells were formed from calcareous plates, which had the thickness of tissue paper and therefore almost did not protect the soft body of the mollusk. Only when their partitions bent? numerous folds, ammonite shells acquired strength and turned into a real shelter from predators. With the complication of partitions, the shells became even more durable, and the external structure made it possible for them to adapt to the most diverse living conditions. Representatives of echinoderms were sea urchins, lilies and stars. At the upper end of the body of sea lilies, there was a flower-like main body. It distinguishes a corolla and grasping organs - “hands”. Between the “hands” in the corolla were the mouth and anus. With “hands” the sea lily raked water into the mouth opening, and with it the sea animals that it fed on. The stem of many Triassic crinoids was spiral. The Triassic seas were inhabited by calcareous sponges, whitefish, leaf-legged crayfish, and ostracods. The fish were represented by sharks living in freshwater bodies and molluscoids inhabiting the sea. The first primitive bony fish appear. Powerful fins, a well-developed dentition, a perfect shape, a strong and light skeleton - all this contributed to the rapid spread of bony fish in the seas of our planet.

Amphibians were represented by stegocephalians from the group of labyrinthodonts. They were sedentary animals with a small body, small limbs and a large head. They lay in the water waiting for the prey, and when the prey approached, they grabbed it. Their teeth had complex labyrinthine folded enamel, which is why they were called labyrinthodonts. The skin was moistened with mucous glands. Other amphibians came out on land to hunt insects. 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 aquatic environment.

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

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

Crocodiles of the Triassic period - small primitive animals of protosuchia - lived in fresh water. Dinosaurs include theropods and prosauropods. Theropods moved on well-developed hind limbs, had a heavy tail, powerful jaws, small and weak forelimbs. In size, these animals ranged from a few centimeters to 15 m. All of them were predators. Prosauropods ate, as a rule, plants. Some of them were omnivores. They walked on four legs. Prosauropods had a small head, long neck and tail. Representatives of the synaptosaur subclass led the most diverse lifestyle. Trilophosaurus climbed trees, fed on plant foods. In appearance, he resembled a cat. Seal-like reptiles lived near the coast, feeding mainly on molluscs. Plesiosaurs lived in the sea, but sometimes came ashore. They reached 15 m in length. They ate fish.

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

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

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

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

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Division of the Triassic system

The Triassic system is divided into 3 sections: lower, middle, upper. The lower section is subdivided into the Indus and Olenyok stages; middle - Anisian, Ladin; upper - Carnian, Norian, Raet.

system	Department	tier	Age, million years ago
Yura	Lower	Goettansky	less
Triassic	Upper	Rhetic	208,5-201,3
		Norian	227-208,5
		Carnian	237-227
	Average	Ladinsky	242-237
		Anisian	247,2-242
	Lower	Oleneksky	251,2-247,2
		Indian	252,2-251,2
Permian	Lopinsky	changxing	more
The division is given in accordance with IUGS as of April 2016.

Geological events

Before the onset of the Triassic, all the continents existed in the form of a single giant supercontinent - Pangea. With the onset of the Triassic, Pangea began to gradually split. In the Triassic, the areas of inland water bodies are greatly reduced, and desert landscapes develop. This period includes the beginning of the deposits of rocks of the Taurian series, which is widespread in the Crimea (undivided Upper Triassic and Lower Jurassic). These rocks make up the lower part of the Crimean Mountains.

• Paleogeographic reconstructions

Climate

A warming climate is causing many inland seas to dry up. Salinity levels are rising in the remaining seas. There is a weakening of climatic zonality and smoothing of temperature differences.

Vegetation

On land, seed ferns continued to dominate. Gymnosperms, cycads, ginkgo and conifers began to become more widespread.

Vegetable world sushi inherited the features of the late Permian era. In the Triassic, tree-like clubmosses and calamites, cordaites, great-ferns, and most of the ancient conifers disappeared. Dipterial ferns, cycads, bennettites, ginkgo, mesophytic conifers, horsetail plants were common.

About half of all land plants disappeared in the Late Triassic.

Animal world

The largest predators are aquatic. At the same time, there is a significant drop in the diversity of vertebrates.

In the late Triassic, a fourth of marine animals died out.

Insects

In the late Triassic, one of the last large orders of insects appears - Diptera, as well as Hymenoptera (the only family Xyelidae, many of whose species die out in the early or middle Jurassic period). The most common are the Mesozoic families Panorpidae, Orthophlebiinae. Along with them, the now extinct Permochoristidae are still quite numerous.

It is known for certain that Orthoptera existed at the end of the Triassic; males of some species had a sound apparatus on the forewings to attract females. At the end of the Triassic, one of the eight families of dragonflies became extinct.

On the border of the Triassic and Juras, synchronously with the great marine extinction, there is also a decline in the diversity of insects, although the main changes in their composition occurred earlier, even in the late Triassic.

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Literature

• Jordan N. N. development of life on earth. - M .: Enlightenment, 1981.
• Koronovsky N.V., Khain V.E., Yasamanov N.A. Historical Geology: Textbook. - M .: Academy, 2006.
• Ushakov S.A., Yasamanov N.A. Continental drift and climates of the Earth. - M .: Thought, 1984.
• Yasamanov N.A. Ancient climates of the Earth. - L.: Gidrometeoizdat, 1985.
• Yasamanov N.A. Popular paleogeography. - M .: Thought, 1985.
• Monin A.S. Popular History of the Earth. - 2nd ed. - M .: Nauka, 1980. - 224 p.
• Ponomarenko, A. G. & Sukacheva, I. D. 2001. Late Triassic-Early Jura insects.

Notes

Links

←	P a l e about h about th	Mesozoic (252.2-66.0 Ma)			To a th n about h about th	→
←		Triassic (252,2-201,3)	Jurassic period (201,3-145,0)	Cretaceous period (145,0-66,0)		→

An excerpt characterizing the Triassic period

Your Excellency, I thought...
- You thought! the prince shouted, pronouncing the words more hastily and more incoherently. - You thought ... Robbers! scoundrels! I will teach you to believe, - and, raising a stick, he swung it at Alpatych and would have hit him if the manager had not involuntarily deviated from the blow. - I thought! Scoundrels! he shouted hastily. But, despite the fact that Alpatych, who himself was frightened of his impudence - to deviate from the blow, approached the prince, obediently lowering his bald head in front of him, or, perhaps, precisely because of this, the prince, continuing to shout: “scoundrels! throw up the road!" did not pick up the stick another time and ran into the rooms.
Before dinner, the princess and m lle Bourienne, who knew that the prince was not in a good mood, stood waiting for him: m lle Bourienne with a beaming face that said: “I don’t know anything, I’m the same as always,” and Princess Mary - pale, frightened, with lowered eyes. The hardest thing for Princess Mary was that she knew that in these cases it was necessary to act like m lle Bourime, but she could not do it. It seemed to her: “If I act as if I don’t notice, he will think that I have no sympathy for him; I will make it so that I myself am boring and out of sorts, he will say (as it happened) that I hung my nose, ”etc.
The prince looked at his daughter's frightened face and snorted.
“Dr… or fool!…” he said.
“And that one isn’t! they’ve been gossiping about her too,” he thought about the little princess, who was not in the dining room.
- Where is the princess? - he asked. - Hiding?...
“She is not quite well,” said m lle Bourienne, smiling cheerfully, “she will not come out. It's so understandable in her position.
- Hm! um! uh! uh! - said the prince and sat down at the table.
The plate seemed to him not clean; he pointed to the stain and dropped it. Tikhon picked it up and handed it to the barman. The little princess was not unwell; but she was so irresistibly afraid of the prince that, hearing how he was in a bad mood, she decided not to go out.
“I am afraid for the child,” she said to m lle Bourienne, “God knows what can be done from fright.
In general, the little princess lived in the Bald Mountains constantly under a feeling of fear and antipathy towards the old prince, which she was not aware of, because fear prevailed so much that she could not feel it. There was also antipathy on the part of the prince, but it was drowned out by contempt. The princess, having settled down in the Bald Mountains, especially fell in love with m lle Bourienne, spent days with her, asked her to spend the night with her, and often spoke with her about her father-in-law and judged him.
- Il nous arrive du monde, mon prince, [Guests are coming to us, prince.] - said m lle Bourienne, unrolling a white napkin with her pink hands. - Son excellence le prince Kouraguine avec son fils, a ce que j "ai entendu dire? [His Excellency Prince Kuragin with his son, how much have I heard?] - she said inquiringly.
“Hm… this excellence boy… I appointed him to the collegium,” the prince said indignantly. - And why the son, I can not understand. Princess Lizaveta Karlovna and Princess Marya may know; I don't know why he's bringing this son here. I don't need. And he looked at the blushing daughter.
- Unhealthy, right? From the fear of the minister, as this blockhead Alpatych said today.
- No, mon pere. [father.]
No matter how unsuccessfully m lle Bourienne got on the subject of conversation, she did not stop and chatted about greenhouses, about the beauty of a new blossoming flower, and the prince softened after the soup.
After dinner he went to his daughter-in-law. The little princess sat at a small table and chatted with Masha, the maid. She turned pale when she saw her father-in-law.
The little princess has changed a lot. She was more bad than good, now. The cheeks drooped, the lip rose up, the eyes were drawn down.
“Yes, some kind of heaviness,” she answered the prince’s question about what she felt.
- Do you need anything?
- No, merci, mon pere. [thank you, father.]
- Well, well, well.
He left and went to the waiter's room. Alpatych, bowing his head, stood in the waiter's room.
- Abandoned road?
- Zakidana, Your Excellency; sorry, for God's sake, for one stupidity.
The prince interrupted him and laughed his unnatural laugh.
- Well, well, well.
He extended his hand, which Alpatych kissed, and went into the office.
In the evening Prince Vasily arrived. He was met on the preshpekt (as the avenue was called) by coachmen and waiters, with a shout they drove his wagons and sledges to the wing along a road deliberately covered with snow.
Prince Vasily and Anatole were given separate rooms.
Anatole was sitting, taking off his camisole and propping himself on his hips, in front of the table, on the corner of which he, smiling, intently and absently directed his beautiful big eyes. He looked at his whole life as an uninterrupted entertainment, which someone for some reason undertook to arrange for him. So now he looked at his trip to the evil old man and to the rich ugly heiress. All this could come out, according to his assumption, very well and funny. And why not marry, if she is very rich? It never interferes, thought Anatole.
He shaved, perfumed himself with the thoroughness and panache that had become his habit, and with a good-natured victorious expression innate in him, carrying his beautiful head high, he entered the room to his father. Near Prince Vasily, his two valets bustled about, dressing him; he himself looked around him animatedly and nodded merrily to his son as he entered, as if he were saying: “So, that’s how I need you!”
- No, no jokes, father, is she very ugly? BUT? he asked, as if continuing a conversation that had been carried on more than once during the journey.
- Full. Nonsense! The main thing is to try to be respectful and prudent with the old prince.
“If he scolds, I will leave,” said Anatole. I can't stand these old people. BUT?
“Remember that everything depends on you.
At that time, the arrival of the minister with his son was not only known in the maid's room, but appearance both of them have already been described in detail. Princess Marya sat alone in her room and tried in vain to overcome her inner agitation.
“Why did they write, why did Lisa tell me about it? After all, this cannot be! she said to herself, looking in the mirror. - How do I get into the living room? Even if I liked him, I could not be myself with him now. Just the thought of her father's gaze horrified her.
The little princess and m lle Bourienne have already received all the necessary information from the maid Masha about what a ruddy, black-browed handsome minister's son was, and about how papa dragged their feet by force to the stairs, and he, like an eagle, walking up three steps, ran after him. Having received this information, the little princess with m lle Bourienne, still audible from the corridor with their animated voices, entered the princess's room.
- Ils sont arrives, Marieie, [They have arrived, Marie,] you know? - said the little princess, waddling her stomach and sinking heavily into an armchair.
She was no longer in the blouse in which she sat in the morning, and she was wearing one of her best dresses; her head was carefully removed, and on her face there was a revival, which, however, did not hide the drooping and dead outlines of her face. In the attire in which she usually went in society in St. Petersburg, it was even more noticeable how much she had grown ugly. On m lle Bourienne, too, there was already imperceptibly some improvement in the outfit, which made her pretty, fresh face even more attractive.

At the end of the Paleozoic, mountain building occurs, which caused the rise of land and the emergence of the Urals and Altai. All this leads to a further increase in the aridity of the climate, which began in the Permian. The land area was much larger than now. Mesozoic is rightly called the era of reptiles.. Their heyday, the widest divergence and extinction occur precisely in this era.

Triassic. In the Triassic, the areas of inland water bodies are greatly reduced, and desert landscapes develop. In an arid climate, many terrestrial organisms die out, in which certain stages of life are associated with water. Most amphibians die out, tree ferns, horsetails and club mosses almost completely disappear. Instead, terrestrial forms begin to predominate, in life cycle which do not have stages associated with water. Among plants in the Triassic, gymnosperms reach strong development, among animals - reptiles.

Of the Triassic reptiles, turtles, crocodiles and tuatara have survived to this day. Hatteria, now preserved only on a few islands near New Zealand, is a real "living fossil". It has changed very little over the past 200 million years and has retained, like its Triassic ancestors, a third eye located in the roof of the skull. In the Triassic, herbivorous and carnivorous dinosaurs. Their size was relatively small; the body length of large Triassic dinosaurs reached 5-6 m, small ones were the size of a chicken.

In the seas, bony fishes develop, while the diversity of cartilaginous and lobe-finned fishes is gradually decreasing. Cephalopods are becoming more and more diverse. The abundance of fish and mollusks allowed some reptiles to master the aquatic environment rich in food. Among water forms the most famous are ichthyosaurs, which, in terms of body structure, very much resembled sharks and modern dolphins.

Along with undoubted progressive features in the organization of reptiles, there is one very significant imperfect feature - unstable body temperature. Downgrading medium temperature reptiles become lethargic, numb. During the entire relatively warm Mesozoic, the unstable body temperature of reptiles was not too much of a negative property. Already in the Triassic, the first representatives of warm-blooded animals appeared - small primitive mammals. Mammals of the Triassic, apparently, were oviparous, like modern echidna and platypus.

Yura. In the Jurassic, there is some expansion of the areas of warm-water seas. In the seas are very numerous cephalopods - ammonites and belemnites. The spiral shell of ammonites is often found in the sediments of the Mesozoic seas. Belemnites somewhat resembled modern squids. The rest of their skeleton ("devil's finger") is common in the sediments of the Mesozoic seas.

Marine reptiles are very diverse. In addition to ichthyosaurs, plesiosaurs appear in the seas of the Jura - animals with a wide body, long flippers and a serpentine neck. Marine reptiles, as it were, divided food resources among themselves: plesiosaurs hunted in the shallow waters of the coastal zone, and ichthyosaurs hunted in the open sea.

In the Jurassic, reptiles began to master the air environment. A variety of flying insects created the conditions for the development of insectivorous flying lizards. Small flying lizards began to feed on large lizards. Flying pangolins existed until the end of the Cretaceous.

At the same time, birds also arose from reptiles in the Jurassic. The first birds found in the Jurassic shales - Archeopteryx - bizarrely combined the signs of reptiles and birds. The head of Archeopteryx resembled the head of a lizard, fingers with claws were preserved on the wings, and there was a long tail. But along with these primitive features, Archeopteryx also had a resemblance to modern birds: the body was covered with feathers that arose from modified scales.

On land in the Jura there are giant herbivorous dinosaurs. The body length of some of them reached 30 m. large sizes reached and hunting for them dinosaurs.

Gymnosperms predominate among plants during this period. Some of them, such as sequoias, have survived to this day.

Chalk. Cretaceous period(or chalk) is named in connection with the formation of chalk in marine sediments of that time. It arose from the remains of the shells of the simplest animals - foraminifera.

In this period, angiosperms arise and spread extremely rapidly, gymnosperms are forced out.

Reptiles were introduced into the Cretaceous by new dinosaurs. Some of them moved on their hind legs and resembled ostriches; gigantic forms were still encountered. Protection from predatory reptiles in some herbivorous dinosaurs went in the direction of gigantism, in others - in the direction of the development of protective tools - horns and bone shields. Some of the herbivorous dinosaurs vaguely resembled rhinos. Flying lizards were very diverse.

The birds still retained their teeth, but otherwise did not differ significantly from modern birds. In the second half of the Cretaceous, marsupials and placental mammals. Long-term bearing of young in the mother's body, nutrition of embryos through the placenta, which connects the bloodstreams of the mother and fetus, are the most important adaptations of mammals to unstable conditions of existence.

Unsteady body temperature and oviposition made reptiles more dependent on fluctuations in environmental temperature, and limited the possibility of their penetration into the polar regions. Having acquired live birth, care for offspring and warm-bloodedness, mammals became less dependent on environmental changes than reptiles. These circumstances led in the Cenozoic to a change in the dominance of reptiles by the dominance of mammals. The acquisition of live birth and warm-bloodedness were those aromorphoses that ensured the progress of mammals.

The widespread distribution of insects and the appearance of the first angiosperms led over time to a relationship between them.

In angiosperms, a flower arose - a reproductive organ that attracts insects with color, smell and nectar reserves. Insects, feeding on nectar, became carriers of pollen. The transfer of pollen by insects, compared with wind pollination, results in less wastage of gametes. The same process of economical use of gametes is also observed in a number of vertebrates. The death of gametes during external fertilization (in fish, amphibians) is much greater than during internal fertilization (in reptiles, birds, mammals).

At the end of the Cretaceous, the climate changes towards sharp continentality and general cooling. Ammonites and belemnites die out in the seas, and after them the sea lizards that fed on them - plesiosaurs and ichthyosaurs. On land, moisture-loving vegetation began to decline, which served as food for herbivorous dinosaurs, which led to their extinction; carnivorous dinosaurs also died out. Of the reptiles, only in the equatorial regions have preserved large forms - crocodiles, turtles and tuatara. Most of the surviving reptiles (lizards, snakes) were small in size.

The Triassic period on Earth lasted about 45 million years. Approximately 220 million years have passed from its beginning to the present day. In the Triassic, land prevailed over the sea. There were two continents. Merged between the North Atlantic and Asian continents formed the Northern land. In the southern hemisphere lay the former Gondwana. Asia joined with Australia and New Zealand. All of Southern Europe, the Caucasus and the Crimea, Iran, the Himalayas and North Africa were flooded by the Tetke ocean. Large mountain ranges did not reappear at this time, but the mountains that had formed in previous periods were still high. There were frequent volcanic eruptions. The climate of the Triassic period was harsh and dry, but warm enough. Deserts in the Triassic are numerous.

Of the plants, gymnosperms noticeably predominated: sago, coniferous and ginkgo. Of the seed ferns, glossopteris continued to exist. At the end of the period, peculiar ferns appeared, especially numerous later on. jurassic, the leaves of which in venation resembled the leaves of seed plants. Triassic horsetails are much closer to modern horsetails than Paleozoic ones.

Great changes have taken place in the life of the inhabitants of the continents. The predominance of land over the sea, which began in the Permian period, and the progressive drying of many fresh water bodies in the Triassic period, led to the fact that many freshwater fish now moved to the seas, and only lungfish, close to the present, still lived in the surviving freshwater basins. At the end of the Triassic, the stegocephalians became extinct. These were the last representatives of the labyrinth-toothed stegocephalians, so named because the enamel on their teeth had a complex folded structure. All stegocephalians, fleeing from a dry climate and from competition with reptiles, became aquatic, and some even moved to live in the sea. Most of them were very large animals. For example, in the Mastodonsaurus, the length of the skull reached 1 m.

At the beginning of the Triassic period, the direct ancestors of modern frogs lived. These protobatrachus are small, 10 cm long, animals, in general structure, they are more like toads than real frogs. Their skin is bumpy, their hind legs are more adapted for swimming than for jumping.

Reptiles have changed especially; whole skulls finally died out. In the second half of the period, the first turtles appeared, which, unlike modern ones, still had teeth in the sky, while the jaws were dressed with a horny beak.

In the Triassic period, they developed intensively, but at the end of it the last animal-like reptiles had already died out. Of these, herbivorous and already completely toothless stahleckers reached the size of a large rhinoceros. The smaller size was a predatory belezodont about 1.5 m long.

Particularly interesting are the small animal-like reptiles Ictidosaurs, close to mammals. So, caromis, an animal the size of a rat, is already a real mammal in the structure of its skull, and only additional bones present in its lower jaw indicate that this animal is still a reptile.

Of the other reptiles in the Triassic period, the trunk-headed ones developed, the closest relatives of the modern New Zealand tuatara, which, although similar to ordinary lizards, differ from them in their structure. Tuatara in its structure still retains many ancient features. In her skull there are two temporal (zygomatic) arches, and not one, like in lizards. Her upper jaw hangs down in the form of a small beak. The teeth on the jaws do not sit in separate cells, but in a common groove. In addition to the usual ribs, "abdominal ribs" also develop on the belly. The biconcave vertebrae resemble the vertebrae of fish. Among the trunkheads in the Triassic lived stenaulorhynchuses - large burrowing animals, possibly feeding on roots. In the seas, along the coasts of the continents, there were long-snouted proboscis - fighters of sea mollusks. In a place with them, placodonts, somewhat reminiscent of sea turtles, hunted for mollusks, in which real millstones for crushing shells formed in the sky instead of small teeth. Related to placodonts, notosaurs also led an aquatic lifestyle. These long-necked animals could still use their paws (flippers) to walk on the ground. Plesiosaurs, common marine reptiles of the following periods, evolved from notosaurs. In northern waters, the first fish lizards, or ichthyosaurs, appeared. They were not yet as well adapted to swimming in the sea as their descendants, in which the tail became like a fish. The most remarkable thing is that ichthyosaurs did not lay eggs like ordinary reptiles, but gave birth to live young, like mammals. From the Triassic, the flowering of a group of cellular reptiles began. The most ancient forms of them were relatively small carnivores. Instead of the usual movement on four legs, these animals adapted to walking on two legs, and therefore their hind legs became much longer than their front ones. Such was Saltoposuchus, an animal larger than 1 m. By the end of the Triassic, some cellular reptiles switched to an aquatic lifestyle. They again began to walk on four legs and in appearance somewhat resembled crocodiles, which were still absent at that time. The length of such a crocodile-like prestosuchus was at least 5 m. The first dinosaurs, not yet very large in size, appeared mainly on the Northern land. Some of them were not small, up to 1m in length, and led a predatory lifestyle. They walked on their hind legs, which were longer than their front ones. In some ways, dinosaurs resembled birds: the bones of their skeleton were hollow, filled with air, and the first toe on the hind legs was turned back.

Other dinosaurs, such as Plateosaurus, were much larger, reaching 6 m in length. The difference in the structure of the front and hind legs is small, their teeth are blunt. These were the ancestors of the herbivorous giants of the Jurassic period.

It is not surprising that with the abundance of animal-like reptiles in the Triassic, we also find here real mammals. The most ancient mammal known to us, the size of a marmot, is called the tritylodont. It belongs to the group of many tubercular mammals, so called because they had numerous tubercles on their molars in two or three rows. They didn't have fangs. One pair of incisors in the upper jaw and a single pair in the lower were enlarged. Many tuberculate teeth ate plant food. Probably still laid eggs, and did not give birth to live Cubs, as well as modern Australian monotreme mammals: platypus and echidna. Modern egg-laying mammals are toothless, but the embryos of the platypus have the rudiments of teeth of a multi-tubercular type. Therefore, many tuberculates are considered the closest relatives of the Australian monotremes, which still retain many features characteristic of reptiles.

At the bottom of the Triassic sea lived numerous six-ray corals, close to modern ones. Bivalves and gastropods were abundant, replacing brachiopods. Often came across new sea urchins and lilies. But numerous ammonites reached a special diversity in this period. At the same time, the first belemnites appeared - animals close to modern cuttlefish, also related to cephalopods. Under their skin, they had a calcareous skeleton in the form of a plate ending in a sharp spike. This spike is usually preserved as a fossil and is called the "devil's finger".

In the sea, in addition to shark fish, quite a lot of bony fish already lived, whose ancestors moved here from fresh water. met here lobe-finned fish and relatives of modern sturgeon fish, as well as armored pikes and silt fish North America. In terms of the structure of the scales, tail and internal organs, these fish still differed from real bony fish.