Origin and evolution of reptiles. Origin and evolution of modern reptiles

In the Upper Triassic, from carnivores that moved mainly on the hind limbs to pseudosuchians (thecodonts); two more groups emerged: lizard-pelvic And Ornithischians are dinosaurs that differ in the details of their pelvic structure. Both groups developed in parallel; in the Jurassic and Cretaceous periods they gave an extraordinary variety of species, ranging in size from rabbits to giants weighing 30-50 tons; lived on land and coastal shallow waters.

By the end Cretaceous period both groups died out without leaving descendants. Big Part were predators that moved on their hind limbs (the heavy tail served as a counterweight); the forelimbs were shortened, often rudimentary. Among them there were giants up to 10-15 m long, armed with powerful teeth and strong claws on the toes of the hind limbs, like a ceratosaurus; despite the big ones dimensions, these predators were very mobile. Some lizard-hipped dinosaurs switched to eating plant foods and moving on both pairs of limbs. These include the largest land animals that have ever existed. So, diplodocus, who had a long tail and a long, mobile neck carrying a small head, 30 m long and probably weighed about 20-25 tons, and the more massive and short-tailed brachiosaurus, with a length of about 24 m, probably weighed at least 50 tons. Such giants apparently slowly They moved on land and most of the time, like modern hippopotamuses, stayed in the coastal areas of water bodies, eating aquatic and surface plants. Here they were protected from attacks by large land predators, and their enormous weight made it possible to successfully withstand the shock of waves.

Ornithischian dinosaurs were probably herbivorous. Most of them retained a bipedal type of locomotion with noticeably shortened forelimbs. Among them, giants 10-15 m long arose, for example iguanodons, in which the first limb has turned into a powerful spike, apparently helped defense against predators. Duck-billed dinosaurs stayed along the banks of water bodies and could run and swim. The front part of the jaws formed a wide duck-like beak, and in the depths of the mouth there were numerous flattened teeth that ground plant food. Other ornithischians, having retained herbivory, again returned to four-legged walking. They often developed protective education against large predators. So, in a stegosaurus that reached 6 m - on back there were two rows of large triangular bone plates, and on the powerful tail there were sharp bone spikes more than 0.5 m long. Triceratops had a powerful horn on the nose and on the horn above the eyes, A The posterior extended edge of the skull, which protected the neck, bore numerous pointed processes.

Finally, the last branch of reptiles - the subclass animal-like, or synapsids - was almost the first to separate from the general trunk of reptiles. They separated from the primitive Carboniferous cotylosaurs, which apparently inhabited wet biotopes and still retained many amphibious features (skin rich in glands, the structure of the limbs, etc.). Synapsids began a special line of reptilian development. Already in the Upper Carboniferous and Permian there arose various forms, united in the order pelycosaurs. They had amphicoelous vertebrae, a skull with a poorly developed one fossa and one occipital condyle, teeth were also present on the palatine bones, and there were abdominal ribs. In appearance they resembled lizards, their length did not exceed 1 m; only single species reached 3-4 m in length. Among them were true predators and herbivorous forms; many led a terrestrial lifestyle, but there were semi-aquatic and aquatic forms.

TO end Perm pelycosaurs became extinct, but earlier the beast-toothed reptiles, therapsids, separated from them. The adaptive radiation of the latter occurred in the Upper Permian, with continuously increasing competition from progressive reptiles- especially archosaurs. Therapsid sizes varied widely: from a mouse to a large rhinoceros. Among them were herbivores - Moschops: and large predators with powerful fangs - inostracevia (skull length 50 cm) in others. Some small forms had, like rodents, large incisors and, apparently, led a burrowing lifestyle. By the end of the Triassic - the beginning of the Jurassic, diverse and well-armed archosaurs completely replaced the beast-toothed therapsids. But already in the Triassic, some group of small species, probably inhabiting damp, densely overgrown biotopes and capable of digging shelters, gradually acquired the features of a more progressive organization and gave rise to mammals.

Thus, as a result of adaptive radiation, already at the end of the Permian - beginning of the Triassic, a diverse fauna of reptiles (about 13-15 orders) emerged, displacing most groups of amphibians. The heyday of reptiles was secured a series of aromorphoses that affected all organ systems and provided increased mobility, intensified metabolism, greater resistance to a number of environmental factors (dryness in the first place), some complication of behavior and better survival of the offspring. The formation of temporal pits was accompanied by an increase in the mass of the chewing muscles, which, along with other transformations, made it possible to expand the range of food used, especially plant foods. Reptiles have not only extensively mastered the land, populating a variety of habitat, but returned to the water and rose into the air. Throughout the Mesozoic era - for more than 150 million years - they occupied the dominant position in almost all terrestrial and many aquatic biotopes. At the same time, the composition of the fauna changed all the time: ancient groups died out, replaced by more specialized young forms.

By the end of the Cretaceous period on earth has begun a new powerful cycle of mountain building (alpine), accompanied by extensive transformations of landscapes and redistribution of seas and land, an increase in the overall dryness of the climate and an increase in its contrasts both in the seasons of the year and And By natural areas. At the same time, the vegetation changed: the dominance of cycads and conifers is replaced by the dominance of angiosperm flora, the fruits and seeds of which have a high aft value. These changes could not but affect the animal world, especially since by this time two new classes of warm-blooded vertebrates had already formed - mammals and birds. The specialized groups of large reptiles that survived until this time could not adapt to changing living conditions. In addition, increasing competition with smaller but active birds and mammals played an active role in their extinction. These classes, having acquired warm-bloodedness, steadily high level metabolism and more challenging behavior, increased in number and importance in communities. They quickly and efficiently adapted to life in changing landscapes, quickly mastered new habitats, intensively used new food, and had an increasing competitive effect on more inert reptiles. The modern Cenozoic era, in which birds and mammals occupied a dominant position, and among reptiles only relatively small and mobile scaly ones (lizards and snakes), well-protected turtles remained And a small group of aquatic archosaurs called crocodiles.

Literature: Zoology of vertebrates. Part 2. Reptiles, birds, mammals. Naumov N.P., Kartashev N.N., Moscow, 1979

Origin of reptiles

Origin of reptiles- one of the important issues in the theory of evolution, the process as a result of which the first animals belonging to the class Reptilia appeared.

Varanus niloticus ornatus at London Zoo

Permian period

From the Upper Permian deposits North America, Western Europe, Russia and China know the remains of cotylosaurs ( Cotylosauria). In a number of characteristics they are still very close to stegocephals. Their skull was in the form of a solid bone box with openings only for the eyes, nostrils and parietal organ, cervical region the spine was poorly formed (although there is a structure of the first two vertebrae characteristic of modern reptiles - atlanta And epistrophy), the sacrum had from 2 to 5 vertebrae; the cleithrum, a skin bone characteristic of fish, was preserved in the shoulder girdle; the limbs were short and widely spaced.

The further evolution of reptiles was determined by their variability due to the influence of various living conditions that they encountered during reproduction and settlement. Most groups became more mobile; their skeleton became lighter, but at the same time stronger. Reptiles consumed a more varied diet than amphibians. The technique of its extraction has changed. In this regard, the structure of the limbs, axial skeleton and skull underwent significant changes. For the majority, the limbs became longer, and the pelvis, gaining stability, was attached to two or more sacral vertebrae. The “fishy” bone, the cleithrum, has disappeared from the shoulder girdle. The solid shell of the skull has undergone partial reduction. In connection with the more differentiated muscles of the jaw apparatus, pits and bone bridges separating them appeared in the temporal region of the skull - arches that served to attach a complex system of muscles.

Synapsids

The main ancestral group that gave rise to all the diversity of modern and fossil reptiles were cotylosaurs, but the further development of reptiles followed different paths.

Diapsids

The next group to separate from the cotylosaurs were the Diapsida. Their skull has two temporal cavities, located above and below the postorbital bone. Diapsids at the end of the Paleozoic (Permian) gave an extremely broad adaptive radiation to systematic groups and species, which are found both among extinct forms and among living reptiles. Among diapsids, two main groups emerged: Lepidosauromorpha and Archosauromorpha. The most primitive diapsids from the group of Lepidosaurs are the order Eosuchia ( Eosuchia) - were the ancestors of the Beak-headed order, from which only one genus is currently preserved - hatteria.

At the end of the Permian, squamate (Squamata) separated from the primitive diapsids, becoming numerous in the Cretaceous period. By the end of the Cretaceous period, snakes evolved from lizards.

Origin of archosaurs

Notes

Literature

Naumov N.P., Kartashev N.N. Part 2. Reptiles, birds, mammals // Zoology of vertebrates. - M.: graduate School, 1979. - P. 272.

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Late Devonian. These were armored-headed amphibians (the outdated name is stegocephals; now most of these animals are included in the labyrinthodonts). They lived near bodies of water and were closely associated with them, since they reproduced only in water. The development of spaces remote from bodies of water required a significant restructuring of the organization: adaptation to protecting the body from desiccation, breathing atmospheric oxygen, efficient movement on solid substrate, and the ability to reproduce outside of water. These are the main prerequisites for the emergence of a qualitatively different new group of animals - reptiles. These changes were quite complex; for example, it required the development of powerful lungs and a change in the nature of the skin.

From the point of view of a progressive method of classification - cladistics, which considers the position of organisms from the point of view of their origin, and not the characteristics of their organization (in particular, the classic “reptilian” characteristics of crocodiles, such as cold-bloodedness and limbs located on the sides of the body, are secondary), reptiles are all developed amniotes, excluding taxa included in the clade synapsids and possibly anapsids.

Carboniferous period

The remains of the most ancient reptiles are known from the Upper Carboniferous (about 300 million years ago). It is assumed that the separation from amphibian ancestors should have begun, apparently, in the Middle Carboniferous (320 million years), when from anthracosaurs like Diplovertebron, forms became isolated, apparently better adapted to the terrestrial way of life. From such forms a new branch arises - the Seymouriomorpha, the remains of which were found in the Upper Carboniferous - Middle Permian. Some paleontologists classify these animals as amphibians.

Permian period

Remains of cotylosaurs (Cotylosauria) are known from the Upper Permian deposits of North America, Western Europe, Russia and China. In a number of characteristics they are still very close to stegocephals. Their skull was in the form of a solid bone box with openings only for the eyes, nostrils and parietal organ, the cervical spine was poorly formed (although there is a structure of the first two vertebrae characteristic of modern reptiles - atlanta And epistrophy), the sacrum had from 2 to 5 vertebrae; the cleithrum, a skin bone characteristic of fish, was preserved in the shoulder girdle; the limbs were short and widely spaced.

Synapsids

The main ancestral group that gave rise to all the diversity of modern and fossil reptiles was probably cotylosaurs, but the further development of reptiles followed different paths.

Diapsids

The next group to separate from the cotylosaurs were the Diapsida. Their skull has two temporal cavities, located above and below the postorbital bone. Diapsids at the end of the Paleozoic (Permian) gave an extremely broad adaptive radiation to systematic groups and species, which are found both among extinct forms and among living reptiles. Among diapsids, two main groups have emerged: lepidosauromorphs (Lepidosauromorpha) and archosauromorphs (Archosauromorpha). The most primitive diapsids from the group of lepidosaurs - the order Eosuchia - were the ancestors of the order Beaked, from which only one genus is currently preserved - hatteria.

At the end of the Permian, squamate (Squamata) separated from the primitive diapsids, becoming numerous in the Cretaceous period. By the end of the Cretaceous period, snakes evolved from lizards.

Origin of archosaurs

Notes

Literature

Naumov N. P., Kartashev N. N. Part 2. Reptiles, birds, mammals// Zoology of vertebrates. - M.: Higher School, 1979. - P. 272.

Transitional form

A transitional form is an organism with an intermediate state that necessarily exists during a gradual transition from one biological type of structure to another. Transitional forms are characterized by the presence of more ancient and primitive (in the sense of primary) traits than their later relatives, but, at the same time, the presence of more progressive (in the sense of later) traits than their ancestors. As a rule, when speaking about intermediate forms, they mean fossil species, although intermediate species do not necessarily have to die out. Many transitional forms are known, illustrating the origin of tetrapods from fish, reptiles from amphibians, birds from dinosaurs, mammals from theriodonts, cetaceans from terrestrial mammals, horses from a five-toed ancestor and humans from ancient hominids.

Reptiles

Reptiles, or reptiles (Latin: Reptilia), are a class of predominantly terrestrial vertebrates, including modern turtles, crocodiles, beaked animals and squamates. Cladists are classified as reptiles and birds, since otherwise the former would be a paraphyletic group.

IN XVIII-XIX centuries together with amphibians, reptiles - cold-blooded terrestrial vertebrates - were united in a group. Traditionally, this group included various vertebrates, which, according to initial ideas, were similar in their organization to modern reptiles(for example, some synapsids - ancestors modern mammals). However, at present, questions about the physiology of many extinct groups of organisms remain open, and data on their genetic and evolutionary relationships do not support this kind of classification.

Many authors who adhere to traditional taxonomy believe that archosaurs (crocodiles, pterosaurs, dinosaurs, etc.) should be removed from the class of reptiles and combined into one class with birds, since birds are actually a specialized group of dinosaurs. About 10,885 species of non-avian reptiles are known in the world; 77 species live in Russia.

The largest land animals belonged to dinosaurs - representatives of ancient reptiles, currently represented only by birds. Reptiles flourished during the Mesozoic era, when they dominated the land, sea and air. At the end of the Cretaceous period, most reptiles became extinct. Modern non-avian reptiles are only scattered remnants of that world. However, ancient reptiles gave rise to the currently thriving group of animals - birds, and many of the adaptations that determined the evolutionary success of this group appeared in its archosaur ancestors, which were a specialized group of diapsids (warm-blooded, heat-insulating body cover - feathers, a developed brain, and etc).

). They lived near bodies of water and were closely associated with them, since they reproduced only in water. The development of spaces remote from bodies of water required a significant restructuring of the organization: adaptation to protecting the body from desiccation, breathing atmospheric oxygen, efficient movement on solid substrate, and the ability to reproduce outside of water. These are the main prerequisites for the emergence of a qualitatively different new group of animals - reptiles. These changes were quite complex; for example, it required the development of powerful lungs and a change in the nature of the skin.

Carboniferous period

The remains of the most ancient reptiles are known from the Upper Carboniferous (about 300 million years ago). It is assumed that the separation from amphibian ancestors should have begun, apparently, in the Middle Carboniferous (320 million years), when from anthracosaurs like Diplovertebron, forms became isolated, apparently better adapted to the terrestrial way of life. From such forms a new branch arises - seymuriomorphs ( Seymouriomorpha), the remains of which were found in the Upper Carboniferous - Middle Permian. Some paleontologists classify these animals as amphibians.

Permian period

From the Upper Permian deposits of North America, Western Europe, Russia and China, remains of cotylosaurs are known ( Cotylosauria). In a number of characteristics they are still very close to stegocephals. Their skull was in the form of a solid bone box with openings only for the eyes, nostrils and parietal organ, the cervical spine was poorly formed (although there is a structure of the first two vertebrae characteristic of modern reptiles - atlanta And epistrophy), the sacrum had from 2 to 5 vertebrae; the cleithrum, a skin bone characteristic of fish, was preserved in the shoulder girdle; the limbs were short and widely spaced.

Synapsids

The main ancestral group that gave rise to all the diversity of modern and fossil reptiles were cotylosaurs, but the further development of reptiles followed different paths.

Diapsids

The next group to split off from the cotylosaurs were the diapsids ( Diapsida). Their skull has two temporal cavities, located above and below the postorbital bone. Diapsids at the end of the Paleozoic (Permian) gave an extremely broad adaptive radiation to systematic groups and species, which are found both among extinct forms and among living reptiles. Among diapsids, two main groups emerged: Lepidosauromorphs ( Lepidosauromorpha) and Archosauromorphs ( Archosauromorpha). The most primitive diapsids from the group of Lepidosaurs are the order Eosuchia ( Eosuchia) - were the ancestors of the Beak-headed order, from which only one genus is currently preserved - hatteria.

At the end of the Permian, squamosids separated from primitive diapsids ( Squamata), which became numerous during the Cretaceous period. By the end of the Cretaceous period, snakes evolved from lizards.

Origin of archosaurs

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Notes

Literature

Naumov N. P., Kartashev N. N. Part 2. Reptiles, birds, mammals // Zoology of vertebrates. - M.: Higher School, 1979. - P. 272.





Evolutionary processes

Factors of evolution

Population genetics

Origin of life

Historical concepts

Modern theories

Evolution of taxa

Excerpt characterizing the Origin of Reptiles

He wanted to say something else, but at that time Prince Vasily stood up with his daughter, and two young men stood up to give them way.
“Excuse me, my dear Viscount,” said Prince Vasily to the Frenchman, affectionately pulling him down by the sleeve to the chair so that he would not get up. “This unfortunate holiday at the envoy’s place deprives me of pleasure and interrupts you.” “I’m very sad to leave your delightful evening,” he said to Anna Pavlovna.
His daughter, Princess Helen, lightly holding the folds of her dress, walked between the chairs, and the smile shone even brighter on her beautiful face. Pierre looked with almost frightened, delighted eyes at this beauty as she passed by him.
“Very good,” said Prince Andrei.
“Very,” said Pierre.
Passing by, Prince Vasily grabbed Pierre's hand and turned to Anna Pavlovna.
“Give me this bear,” he said. “He’s been living with me for a month, and this is the first time I’ve seen him in the world.” Nothing is needed young man, as a society of smart women.

Anna Pavlovna smiled and promised to take care of Pierre, who, she knew, was related to Prince Vasily on his father’s side. The elderly lady, who had previously been sitting ma tante, hastily stood up and caught up with Prince Vasily in the hallway. All the previous pretense of interest disappeared from her face. Her kind, tear-stained face expressed only anxiety and fear.
- What will you tell me, prince, about my Boris? – she said, catching up with him in the hallway. (She pronounced the name Boris with special emphasis on the o). – I can’t stay longer in St. Petersburg. Tell me, what news can I bring to my poor boy?
Despite the fact that Prince Vasily listened reluctantly and almost discourteously to the elderly lady and even showed impatience, she smiled tenderly and touchingly at him and, so that he would not leave, took his hand.
“What should you say to the sovereign, and he will be directly transferred to the guard,” she asked.
“Believe me, I will do everything I can, princess,” answered Prince Vasily, “but it’s difficult for me to ask the sovereign; I would advise you to contact Rumyantsev, through Prince Golitsyn: that would be smarter.
The elderly lady bore the name of Princess Drubetskaya, one of the best families in Russia, but she was poor, had long since left the world and had lost her previous connections. She has now come to secure appointment to her guard only son. Only then, in order to see Prince Vasily, did she introduce herself and come to Anna Pavlovna for the evening, only then did she listen to the Viscount’s story. She was frightened by the words of Prince Vasily; once upon a time Beautiful face she expressed anger, but this lasted only a minute. She smiled again and grabbed Prince Vasily’s hand more tightly.
“Listen, prince,” she said, “I never asked you, I will never ask you, I never reminded you of my father’s friendship for you.” But now, I conjure you by God, do this for my son, and I will consider you a benefactor,” she hastily added. - No, you are not angry, but you promise me. I asked Golitsyn, but he refused. Soyez le bon enfant que vous аvez ete, [Be the kind fellow you were,] she said, trying to smile, while there were tears in her eyes.
“Dad, we’ll be late,” she said, turning her beautiful head on antique shoulders, Princess Helen, waiting at the door.
But influence in the world is capital, which must be protected so that it does not disappear. Prince Vasily knew this, and once he realized that if he began to ask for everyone who asked him, then soon he would not be able to ask for himself, he rarely used his influence. In the case of Princess Drubetskaya, however, after her new call, he felt something like a reproach of conscience. She reminded him of the truth: he owed his first steps in the service to her father. In addition, he saw from her methods that she was one of those women, especially mothers, who, once they have taken something into their heads, will not leave until their desires are fulfilled, and otherwise are ready for daily every minute harassment and even on stage. This last consideration shook him.
“Here Anna Mikhailovna,” he said with his usual familiarity and boredom in his voice, “it’s almost impossible for me to do what you want; but to prove to you how much I love you and honor the memory of your late father, I will do the impossible: your son will be transferred to the guard, here is my hand to you. Are you satisfied?
- My dear, you are a benefactor! I didn’t expect anything else from you; I knew how kind you were.
He wanted to leave.
- Wait, two words. Une fois passe aux gardes... [Once he joins the guard...] - She hesitated: - You are good with Mikhail Ilarionovich Kutuzov, recommend Boris to him as an adjutant. Then I would be calm, and then I would...
Prince Vasily smiled.
- I don’t promise that. You don’t know how Kutuzov has been besieged since he was appointed commander-in-chief. He himself told me that all the Moscow ladies agreed to give him all their children as adjutants.
- No, promise me, I won’t let you in, my dear, my benefactor...
- Dad! - the beauty repeated again in the same tone, - we will be late.
- Well, au revoir, [goodbye,] goodbye. Do you see?
- So tomorrow you will report to the sovereign?
- Definitely, but I don’t promise Kutuzov.
“No, promise, promise, Basile, [Vasily,],” Anna Mikhailovna said after him, with the smile of a young coquette, which once must have been characteristic of her, but now did not suit her exhausted face.
She apparently forgot her years and, out of habit, used all the old feminine remedies. But as soon as he left, her face again took on the same cold, feigned expression that was on it before. She returned to the circle, in which the Viscount continued to talk, and again pretended to listen, waiting for the time to leave, since her work was done.
– But how do you find all this latest comedy du sacre de Milan? [Milan anointing?] - said Anna Pavlovna. Et la nouvelle comedie des peuples de Genes et de Lucques, qui viennent presenter leurs voeux a M. Buonaparte assis sur un throne, et exaucant les voeux des nations! Adorable! Non, mais c"est a en devenir folle! On dirait, que le monde entier a perdu la tete. [And here is a new comedy: the peoples of Genoa and Lucca express their desires to Mr. Bonaparte. And Mr. Bonaparte sits on the throne and fulfills the desires of the peoples. 0! this is amazing! No, you can go crazy from this. You will think that the whole world has lost its head.]
Prince Andrei grinned, looking straight into Anna Pavlovna’s face.
“Dieu me la donne, gare a qui la touche,” he said (the words Bonaparte said when laying on the crown). “On dit qu"il a ete tres beau en prononcant ces paroles, [God gave me the crown. Trouble is the one who touches it. “They say he was very good in saying these words,” he added and repeated these words again in Italian: “Dio mi la dona, guai a chi la tocca.”
“J"espere enfin," Anna Pavlovna continued, "que ca a ete la goutte d"eau qui fera deborder le verre. Les souverains ne peuvent plus supporter cet homme, qui menace tout. [I hope that this was finally the drop that overflows the glass. The sovereigns can no longer tolerate this man who threatens everything.]
– Les souverains? Je ne parle pas de la Russie,” said the Viscount politely and hopelessly: “Les souverains, madame!” Qu"ont ils fait pour Louis XVII, pour la reine, pour Madame Elisabeth? Rien,” he continued animatedly. “Et croyez moi, ils subissent la punition pour leur trahison de la cause des Bourbons. Les souverains? Ils envoient des ambassadeurs complimenter l"usurpateur. [Sirs! I'm not talking about Russia. Sirs! But what did they do for Louis XVII, for the queen, for Elizabeth? Nothing. And, believe me, they are being punished for their betrayal of the Bourbon cause. Sirs! They send envoys to greet the thief of the throne.]
And he, sighing contemptuously, changed his position again. Prince Hippolyte, who had been looking at the Viscount through his lorgnette for a long time, suddenly at these words turned his whole body to the little princess and, asking her for a needle, began to show her, drawing with a needle on the table, the coat of arms of Condé. He explained this coat of arms to her with such a significant air, as if the princess had asked him about it.
- Baton de gueules, engrele de gueules d "azur - maison Conde, [A phrase that is not translated literally, as it consists of conventional heraldic terms that are not used entirely accurately. The general meaning is this: The coat of arms of Conde represents a shield with red and blue narrow jagged stripes ,] - he said.

Some representatives of this group of historical animals were the size of an ordinary cat. But the height of others can be compared with a five-story building.

Dinosaurs... Probably one of the most interesting groups animals throughout the history of the development of the Earth's fauna.

The ancestors of reptiles are considered to be batrachosaurs, fossil animals found in Permian deposits. This group includes, for example, Seymouria. These animals had characteristics intermediate between amphibians and reptiles. The outlines of their teeth and skull were typical of amphibians, and the structure of the spine and limbs was typical of reptiles. Seymouria spawned in the water, although she spent almost all her time on land. Her offspring developed into adults through the process of metamorphosis, which is typical of modern frogs. The limbs of Seymouria were more developed than those of early amphibians, and it easily moved along muddy soil, stepping on its five-toed paws. It ate insects, small animals, and sometimes even carrion. The fossilized contents of Seymouria's stomach indicate that it sometimes happened to eat its own kind.

From Batrachosaurs came the first reptiles, the cotylosaurs, a group of reptiles that included reptiles that had a primitive skull structure.

Large cotylosaurs were herbivores and lived, like hippopotamuses, in swamps and river backwaters. Their heads had projections and ridges. They could probably bury themselves in the mud right up to their eyes. Fossil skeletons of these animals were discovered in Africa. Russian paleontologist Vladimir Prokhorovich Amalitsky was fascinated by the idea of finding African dinosaurs in Russia. After four years of research, he managed to find dozens of skeletons of these reptiles on the banks of the Northern Dvina.

From cotylosaurs during Triassic period(V Mesozoic era) many new groups of reptiles appeared. Turtles still retain a similar skull structure. All other orders of reptiles originate from cotylosaurs.

Beast-like lizards. At the end of the Permian period, a group of animal-like reptiles flourished. The skull of these animals was distinguished by one pair of lower temporal fossae. Among them were large four-legged forms (it’s hard to even call them “reptiles” in exact value this word). But there were also small forms. Some were carnivores, others were herbivores. The predatory lizard Dimetrodon had powerful wedge-shaped teeth.

Characteristic animal - a leathery crest starting from the spine, reminiscent of a sail. It was supported by long bony extensions extending from each vertebra. The sun warmed the blood circulating in the sail, and it transferred heat to the body. Possessing two types of teeth, Dimetrodon was a ferocious predator. The razor-sharp front teeth pierced the body of the victim, and the short and sharp back teeth were used for chewing food.

Among the lizards of this group, animals with teeth appeared for the first time different types: incisors, canines and molars. They were called beast-toothed. The predatory three-meter lizard with fangs more than 10 cm long received its name in honor of the famous geologist Professor A.A. Inostrantseva. Predatory beast-toothed lizards (theriodonts) are already very similar to primitive mammals, and it is no coincidence that the first mammals developed from them by the end of the Triassic.

Dinosaurs are reptiles with two pairs of temporal pits in the skull. These animals, having appeared in the Triassic, received significant development in subsequent periods of the Mesozoic era (Jurassic and Cretaceous). Over 175 million years of development, these reptiles have given a huge variety of forms. Among them were both herbivorous and predatory, mobile and slow. Dinosaurs are divided into two orders: saurischians and ornithischians.

Lizard-hipped dinosaurs walked on their hind legs. They were fast and agile predators. Tyrannosaurus (1) reached a length of 14 m and weighed about 4 tons. Small carnivorous dinosaurs– coelurosaurs (2) were similar to birds. Some of them had a cover of hair-like feathers (and perhaps constant temperature body). The lizard-hatched dinosaurs also include the largest herbivorous dinosaurs - brachiosaurs (up to 50 tons), which had a small head on long neck. 150 million years ago, a thirty-meter diplodocus, the largest animal ever known, lived in lakes and river banks. To facilitate movement, these huge reptiles spent most of their time in water, that is, they led an amphibious lifestyle.

Ornithischian dinosaurs ate exclusively plant foods. Iguanodon also walked on two legs, its forelimbs were shortened. On the first toe of its forelimbs there was a large spike. Stegosaurus (4) had a small head and two rows of bony plates along its back. They served him as protection and carried out thermoregulation.

At the end of the Triassic, the first crocodiles arose from the descendants of cotilosaurs, which became widespread only in the Jurassic period. At the same time, flying lizards appeared - pterosaurs, also descending from thecodonts. On their five-fingered forelimb, the last finger was able to make a special impression: very thick and equal in length... to the length of the animal’s body including the tail.

A leathery flight membrane was stretched between it and the hind limbs. Pterosaurs were numerous. Among them were species that were quite comparable in size to our ordinary birds. But there were also giants: with a wingspan of 7.5 m. Among the flying dinosaurs of the Jurassic, the most famous are Rhamphorhynchus (1) and Pterodactyl (2); of the Cretaceous forms, the most interesting is the relatively very large Pteranodon. By the end of the Cretaceous, flying lizards became extinct.

Among the reptiles there were also aquatic lizards. Large fish-like ichthyosaurs (1) (8–12 m) with a spindle-shaped body, flipper-like limbs, and a fin-like tail - in general outline they resembled dolphins. Plesiosaurs (2) distinguished by their elongated necks probably inhabited coastal seas. They ate fish and shellfish.

It's interesting that in Mesozoic deposits remains of lizards very similar to modern ones were discovered.

In the Mesozoic era, which was characterized by a particularly warm and even climate, primarily in Jurassic period, reptiles have reached their greatest prosperity. In those days, reptiles occupied the same high place in nature as mammals occupy in the modern fauna.

About 90 million years ago they began to die out. And 65–60 million years ago, only four modern orders remained from the former splendor of reptiles. Thus, the decline of reptiles continued for many millions of years. This was probably due to the deterioration of the climate, change of vegetation, and competition from animals of other groups that had such important advantages as a more developed brain and warm-bloodedness. Of the 16 orders of reptiles, only 4 have survived! About the rest, only one thing can be said: their adaptations were clearly not enough to meet the new circumstances. A striking example of the relativity of any device!

However, the heyday of reptiles was not in vain. After all, they were the necessary link for the emergence of new, more advanced classes of vertebrate animals. Mammals evolved from lizard-toothed dinosaurs, and birds evolved from saurian dinosaurs.

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