The period characterized by the beginning of the flowering of ancient reptiles is called. The era of ancient reptile giants. The largest and smallest turtles
home
; perhaps they have already begun to become keratinized.
It is not yet clear when the inherent pattern of reproduction and development of eggs in the air environment, characteristic of amniotes, took shape. It can be assumed that this happened in the Carboniferous during the formation of cotylosaurs - Cotylosauria. Among them were small lizard-like forms that apparently fed on various invertebrates, and large (up to 3 m long) massive herbivorous pareiasaurs such as the Severodvinsk scutosaurus. Some cotylosaurs led a semi-aquatic lifestyle, inhabiting humid biotopes, while others, apparently, became true terrestrial inhabitants.
Warm and humid climate Carboniferous favored amphibians. At the end of the Carboniferous - beginning of the Permian, intense mountain building (uplift of the mountains of the Urals, Carpathians, Caucasus, Asia and America - the Hercynian cycle) was accompanied by dismemberment of the relief, increased zonal contrasts (cooling in high latitudes), a decrease in the area of wet biotopes and an increase in the proportion of dry biotopes. This contributed to the emergence of terrestrial vertebrates.
The main ancestral group that gave rise to all the diversity of fossils and modern reptiles were the above-mentioned cotylosaurs. Having reached their peak in the Permian, they, however, became extinct by the middle of the Triassic, apparently under the influence of competitors - various progressive groups of reptiles that separated from them. In the Permian, turtles separated from cotylosaurs - Chelonia - their only direct descendants that have survived to this day. In the first turtles, such as the Permian Eunotosaurus, the sharply expanded ribs do not yet form a continuous dorsal shell. Seymuriomorphs, cotylosaurs and turtles are grouped into the subclass Anapsida.
Apparently, in the Upper Carboniferous, two subclasses of reptiles evolved from cotylosaurs, which again switched to an aquatic lifestyle:
Order of mesosaurs.
Order of ichthyosaurs.
The subclass of synaptosaurs, Synaptosauria, includes two orders. order protorosaurs - Protorosauria order sauropterygia - Sauropterygia These include nothosaurs and plesiosaurs.
Proganosaurs and synaptosaurs went extinct without leaving descendants.
In the Permian, a large branch of diapsid reptiles separated from cotylosaurs, in the skull of which two temporal pits formed; this group subsequently split into two subclasses: the lepidosaur subclass and the archosaur subclass.
The most primitive diapsids are the order of eosuchians - Eosuchia of the subclass Lepidosauria - small (up to 0.5 m), lizard-like reptiles; had amphicoelous vertebrae and small teeth on the jaws and palatine bones; went extinct at the beginning of the Triassic. In the Permian, beak-headed animals, Rhynchocephalia, separated from some eosuchians, distinguished by large temporal pits, a small beak at the end of the upper jaws and hook-shaped processes on the ribs. Beakheads became extinct at the end of the Jurassic, but one species - the New Zealand tuateria - has survived to this day.
At the end of the Permian, squamate - Squamata (lizards), became numerous and diverse in the Cretaceous, separated from primitive diapsids (possibly directly from eosuchians). At the end of this period, snakes evolved from lizards. The flourishing of scaly ones occurs in Cenozoic era; they make up the vast majority of living reptiles.
The most diverse in forms and ecological specialization in Mesozoic era was a subclass of archosaurs called Archosauria. Archosaurs inhabited land, bodies of water, and conquered the air. The original group of archosaurs were thecodonts - Thecodontia (or pseudosuchians), which separated from the eosuchians, apparently in the Upper Permian and reached their peak in the Triassic. They looked like lizards ranging from 15 cm to 3-5 m in length, most led a terrestrial lifestyle; the hind limbs were usually longer than the forelimbs. Some of the thecodonts (ornithosuchians) probably climbed branches and led an arboreal lifestyle; Apparently, the class of birds later evolved from them. Another part of the thecodonts switched to a semi-aquatic lifestyle; From them, at the end of the Triassic, crocodiles arose - Crocodilia, which formed many different forms in the Jurassic - Cretaceous.
In the mid-Triassic, the thecodonts gave rise to flying dinosaurs, or pterosaurs, Pterosauria; Pterosaurs were widespread and numerous during the Jurassic and Cretaceous periods; completely died out, leaving no descendants, by the end of the Cretaceous. The extinction may have been facilitated by competition with the increasingly numerous birds at that time. It should be emphasized that pterosaurs and birds are completely independent branches of evolution, the ancestral forms of which were different families of the thecodont order.
In the Upper Triassic, two more groups separated from the carnivores that moved primarily on the hind limbs of pseudosuchians (thecodonts): saurischian dinosaurs - Saurischia and ornithischian dinosaurs - Ornithischia. Saurischian and ornithischian dinosaurs differed in the details of the structure of the pelvis. 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.
Finally, the last branch of reptiles - the subclass animal-like, or synapsids - Theromorpha or Synapsida, 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 of pelycosaurs - Pelycosauria. They had amphicoelous vertebrae, a skull with a poorly developed one fossa and one occipital condyle, there were teeth on the palatine bones, and there were abdominal ribs. By appearance they looked like 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. By the end of the Permian, pelycosaurs became extinct, but before that the beast-toothed reptiles - therapsids - Therapsida separated from them. The adaptive radiation of the latter occurred in the Upper Permian - Triassic, 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 - Inostrancevia (skull length 50 cm; Fig. 5), etc. 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 (approximately 13-15 orders) emerged, displacing most groups of amphibians. The flourishing of reptiles was ensured by a number of aromorphoses, which affected all organ systems and ensured 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 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 not only widely mastered the land, populating a variety of habitats, but returned to the water and rose into the air. Throughout the Mesozoic era - for more than 150 million years - they occupied a 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, 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, a consistently high level of 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 began, in which birds and mammals occupied a dominant position, and among the reptiles only relatively small and mobile scaly ones (lizards and snakes), well-protected turtles and a small group of aquatic archosaurs - crocodiles - were preserved.
Fossil reptiles are of exceptional interest, since they include numerous groups that once dominated the world. globe. Ancient groups of this class gave rise not only to modern reptiles, but also to birds and mammals. The oldest reptiles belonging to the order of cotylosaurs, or whole-skulls (Cotylosauria), from the subclass of anapsids, are already known from the upper Carboniferous deposits, but only in Permian period they achieved significant development, and in the Triassic they already became extinct. Cotylosaurs were massive animals with thick, five-toed legs and body lengths ranging from several tens of centimeters to several meters. The skull was covered with a solid shell of dermal bones with openings only for the nostrils, eyes and parietal organ. This structure of the skull, as well as many other features, indicate the extreme closeness of cotylosaurs to primitive stegocephalians, which undoubtedly were their ancestors. The most primitive of the so far known anapsids, and therefore of reptiles in general, is the Lower Permian Seymouria. This relatively small (up to 0.5 m in length) reptile had a number of features characteristic of amphibians: the neck was almost not pronounced, the long sharp teeth still retained a primitive structure, there was only one sacral vertebra, and the bones of the skull showed remarkable similarities even in details with the cranial cover of stegocephali. Fossil remains of seymuriomorphic reptiles were found in the area former USSR(Kotlasia and others), made it possible for Soviet paleontologists to determine their systematic position as representatives of a special subclass of batrachosaurs (Batrachosauria), occupying an intermediate position between amphibians and cotylosaurs. Cotylosaurs are a very diverse group. The most major representatives Its members are the clumsy herbivorous pareiasaurs (Pareiasaurus), reaching 2-3 m in length. Their skeletons were later found in South Africa and here on the Northern Dvina. Cotylosaurs were the original group that gave rise to all other major groups of reptiles. Evolution mainly proceeded along the path of the emergence of more mobile forms: the limbs began to lengthen, at least two vertebrae took part in the formation of the sacrum, the entire skeleton, while maintaining its strength, became lighter, in particular, the initially solid bone shell of the skull began to be reduced by the appearance of temporal pits, which not only lightened the skull, but, most importantly, helped to strengthen the muscles that compress the jaws, since if a hole is formed in the bone plate to which the muscles are attached, the muscle, when contracting, can protrude somewhat into this hole. The reduction of the cranial shell proceeded in two main ways: by the formation of one temporal fossa, limited below by the zygomatic arch, and by the formation of two temporal fossae, resulting in the formation of two zygomatic arches. Thus, all reptiles can be divided into three groups: 1) anapsids - with a solid cranial shell (cotylosaurs and turtles); 2) synapsids - with one zygomatic arch (animal-like, plesiosaurs and, possibly, ichthyosaurs) and 3) diapsids - with two arches (all other reptiles). The first and second groups each contain one subclass, the latter is divided into a number of subclasses and many orders. The anapsid group is the oldest branch of reptiles, having many skull structures common features with fossil stegocephalians, since not only many of their early forms (cotylosaurs), but even some modern ones (some turtles) have a continuous cranial shell. Turtles are the only living representatives of this ancient group of reptiles. They apparently separated directly from the cotylosaurs. Already in the Triassic, this ancient group was fully formed and, thanks to its extreme specialization, has survived to the present day, almost unchanged, although in the process of evolution, some groups of turtles switched several times from a terrestrial lifestyle to an aquatic one, and therefore they almost lost their bony shields , then acquired them again. From the group of cotylosaurs, marine fossil reptiles separated - ichthyosaurs and plesiosaurs, which, together with other rarer forms, formed two independent subclasses: Ichthyopterygia and Synaptosauria. Plesiosaurs (Plesiosauria), related to synaptosaurs, were marine reptiles. They had a wide, barrel-shaped, flattened body, two pairs of powerful limbs modified into swimming flippers, a very long neck ending in a small head, and a short tail. The skin was bare. Numerous sharp teeth sat in separate cells. The sizes of these animals varied over a very wide range: some species were only half a meter in length, but there were also giants that reached 15 m. Feature their skeleton consisted in the underdevelopment of the dorsal parts of the limb girdles (scapula, ilium) and the exceptional strength of the abdominal girdles (coracoid, abdominal process of the scapula, pubic and ischial bones), as well as the abdominal ribs. All this indicates an exceptionally strong development of the muscles that move the flippers, which served only for rowing and could not support the body out of the water. Although within the subclass of synaptosaurs the transition from terrestrial to aquatic forms has been restored quite clearly, the origin of the group as a whole is still largely unclear. While plesiosaurs, having adapted to aquatic life, still retained the appearance of terrestrial animals, ichthyosaurs (Ichthyosauria), belonging to ichthyopterygians, acquired similarities with fish and dolphins. The body of ichthyosaurs was spindle-shaped, the neck was not pronounced, the head was elongated, the tail had a large fin, and the limbs were in the form of short flippers, with the hind ones being much smaller than the front ones. The skin was bare, numerous sharp teeth (adapted to feeding on fish) sat in a common groove, there was only one zygomatic arch, but of an extremely unique structure. The sizes varied from 1 to 13 m. The diapsid group includes two subclasses: lepidosaurs and archosaurs. The earliest (Upper Permian) and most primitive group of lepidosaurs is the order Eosuchia. They are still very poorly studied, the best known is lounginia - a small reptile, resembling a lizard in body, with relatively weak limbs that had the usual reptilian structure. Its primitive features are expressed mainly in the structure of the skull; teeth are located both on the jaws and on the palate. The first beaked animals (Rhynchocephalia) have been known since the Early Triassic. Some of them were extremely close to the modern hatteria. Beakheads differ from Eosuchians in the presence of a horny beak and in the fact that their teeth are attached to the bone, while the jaw teeth of Eosuchians sat in separate cells. According to the last feature, beakheads are even more primitive than eosuchians and, therefore, should have descended from some not yet found primitive forms last group. Squamata, namely lizards, are known only from the very end of the Jurassic. Mosasauria (Mosasauria) apparently separated from the main trunk of squamate lizards already at the beginning of the Cretaceous. These were sea reptiles that had a long serpentine body and two pairs of limbs modified into flippers. Some representatives of this order reached a length of 15 m. At the end of the Cretaceous they died out without a trace. Somewhat later than the mosasaurs (end of the Cretaceous), a new branch separated from lizards - snakes. In all likelihood, a large progressive branch of archosaurs (Archosauria) originated from Eosuchia - namely pseudosuchia, which subsequently split into three main branches - aquatic (crocodiles), terrestrial (dinosaurs) and airborne (winged lizards). Along with the two typical temporal arches, the most characteristic feature This group had a tendency to switch to “bipedalism,” i.e., moving on only the hind limbs. True, some of the most primitive archosaurs only began to change in this direction, and their descendants took a different path, and representatives of a number of groups returned to moving on four limbs for the second time. But in the latter case, past history has left its mark on the structure of their pelvis and the hind limbs themselves. Pseudosuchia first appeared only at the beginning of the Triassic. The early forms were small animals, but with relatively long hind legs, which, apparently, served them alone for movement. The teeth, which were present only on the jaws, sat in separate cells, and bone plates were almost always located in several rows along the back. These small forms, typical representatives of which are ornithosuchians, and apparently leading the arboreal life of Scleromochlus, were very numerous and gave rise not only to branches that flourished later - in the Jurassic and Cretaceous, but also to a number of highly specialized groups that became extinct without a trace. in the Triassic. Finally, pseudosuchians, in particular, if not Ornithosuchus itself, then forms close to it, could be the ancestors of birds. Crocodiles (Crocodylia) are very close to some Triassic pseudosuchians, such as Belodon, or Phytosaurus. Starting from the Jurassic, real crocodiles appeared, but they finally developed modern type crocodiles only during the Cretaceous period. On this long path of evolution, you can trace step by step how the characteristic feature crocodiles - secondary palate. At first, only horizontal processes appeared on the maxillary and palatine bones, then these palatine processes converged, and even later they were joined by the palatine processes of the pterygoid bones, and simultaneously with this process the nostrils moved forward, and the secondary choanae moved backward. Dinosaurs (Dinosauria) are the most numerous and diverse group of reptiles that have ever lived. These included small forms, the size of a cat and smaller, and giants, reaching almost 30 m in length and 40-50 tons in weight, light and massive, agile and clumsy, predatory and herbivorous, devoid of scales and covered with a bony shell with various outgrowths. Many of them ran galloping on one hind limb, leaning on the tail, while others moved on all four. Dinosaurs' heads were usually relatively small, while the cavity of the cranium was very tiny. But the spinal canal in the sacral area was very wide, which indicates a local expansion of the spinal cord. Dinosaurs were divided into two large groups- lizard and ornithischians, which arose completely independently from pseudosuchians. Their differences lie mainly in the structure of the hind limb girdle. Lizard hippies (Saurischia), family ties which with pseudosuchia there is no doubt, were originally only predatory. Subsequently, although most forms continued to remain carnivorous, some turned into herbivores. Carnivores, although they reached enormous sizes (up to 10 m in length), had a relatively light build and a powerful skull with sharp teeth. Their forelimbs, which apparently served only for grasping prey, were greatly reduced, and the animal had to move by jumping on its hind limbs and leaning on its tail. Typical representative such forms are Ceratosaurus. In contrast to predatory herbivorous forms, they moved on both pairs of limbs, which they had almost equal length and ended in five fingers, apparently covered with horny formations like hooves. These included the largest four-legged animals that ever lived on the globe, such as the Brontosaurus, which reached over 20 m in length and probably 30 tons in weight, and Diplodocus. The latter was slimmer and, undoubtedly, much lighter, but it was superior to the Brontosaurus in length, which in one specimen exceeded 26 m; finally, the lumbering Brachiosaurus, about 24 m long, must have weighed about 50 tons. Although hollow bones lightened the weight of these animals, it is still difficult to believe that such giants could move freely on land. Apparently, they led only a semi-terrestrial life and, like modern hippopotamuses, most spent time in the water. This is indicated by their very weak teeth, suitable for eating only soft aquatic vegetation, and the fact that, for example, Diplodocus's nostrils and eyes were moved upward, so that the animal could see and breathe with only part of its head out of the water. Ornithischia, which had a girdle of hind limbs extremely similar to a bird's, never reached such enormous sizes. But they were even more diverse. Most of these animals returned to moving on four legs for the second time and usually had a well-developed shell, sometimes complicated by various kinds of outgrowths in the form of horns, spines, etc. All of them remained herbivorous from the very beginning to the end, and the majority retained only their back teeth, while the front of the jaws was apparently covered with a horny beak. Iguanodons, stegosaurs and triceratops can be mentioned as characteristic representatives of various groups of ornithischians. Iguanodons, reaching 5-9 m in height, ran on their own hind legs and were deprived of a shell, but the first finger of their forelimbs was a bone spike that could serve as a good weapon of defense. Stegosaurus had a tiny head, a double row of tall triangular bony plates on its back, and several sharp spines perched on its tail. Triceratops looked like a rhinoceros: at the end of its snout there was a large horn, in addition, a pair of horns rose above the eyes, and along the rear, extended edge of the skull there were numerous pointed processes. Pterodactyls (Pterosauria), like birds and bats, were real flying animals. Their forelimbs were real wings, but of an extremely unique structure: not only the forearm, but also the metacarpal bones fused to each other were greatly elongated, the first three fingers had a normal structure and size, the fifth was absent, while the fourth reached extreme length and between them and a thin flying membrane was stretched along the sides of the body. The jaws were extended, some forms had teeth, others had a toothless beak. Pterodactyls exhibit a number of common features with birds: fused thoracic vertebrae, a large sternum with a keel, a complex sacrum, hollow bones, a sutureless skull, and large eyes. The winged lizards apparently ate fish and probably lived on coastal rocks, since, judging by the structure of their hind limbs, they could not rise from a flat surface. Pterodactyls include quite diverse forms: a relatively primitive group of rhamphorhynchus, which had a long tail, and pterodactyls themselves with a rudimentary tail. The sizes ranged from the size of a sparrow to a giant pteranodon, whose wingspan reached 7 m. The group of synapsids constitutes an independent subclass of reptiles, as a special side branch that separated from the ancient cotylosaurs. They are characterized by strengthening of the jaw apparatus by the formation of a kind of temporal cavity for very powerful jaw muscles and progressive differentiation of the dental system - heterodontism, or heterodonty. This connects them with upper class vertebrates - mammals. Animal-like (Theromorpha) is a group whose primitive representatives were still very close to cotylosaurs. Their difference lies mainly in the presence of a zygomatic arch and a lighter build. Animal-like animals appeared at the end of the Carboniferous period, and starting from the Lower Permian they became very numerous and during this entire period, together with cotylosaurs, they were almost the only representatives of their class. Despite all their diversity, all beast-like animals were strictly terrestrial animals, moving exclusively with the help of both pairs of limbs. The most primitive representatives of pelycosaurs (for example, Varanops) were small in size and should have looked like lizards. However, their teeth, although homogeneous, were already sitting in separate cells. The mammals (Therapsida), which replaced the pelycosaurs from the Middle Permian, united extremely diverse animals, many of which were highly specialized. In later forms, the parietal foramen disappeared, the teeth differentiated into incisors, canines and molars, a secondary palate was formed, one condyle was divided into two, the dentary bone increased greatly, while the other bones of the lower jaw decreased. The reasons for the extinction of ancient reptiles are still not entirely clear. The most plausible explanation for this phenomenon is the following. In the process of struggle for existence, individual forms became more and more adapted to certain environmental conditions and became more and more specialized. Such specialization is extremely useful, but only as long as the conditions to which the organism has adapted continue to exist. Once they change, such animals find themselves in worse conditions than the less specialized forms that supplant them in the struggle for existence. In addition, in the struggle for existence, some groups may acquire properties that increase their general vital activity. In contrast to narrow adaptation, or idioadaptation, this phenomenon is called aromorphosis. For example, warm-bloodedness made it possible for organisms that acquired this property to be less dependent on climate compared to animals with variable body temperature. During the long Mesozoic era, there were only minor changes in landscapes and climate, and therefore reptiles became more and more specialized and flourished. But at the end of this era earth's surface began to undergo such huge mountain-building processes and associated climate change that most reptiles could not survive them and died out without a trace by the end of the Mesozoic, which was called the era of the great extinction. However, it would be a mistake to explain this process solely by physical and geographical reasons. An equally important role was played by the struggle for existence with other animals, namely with birds and mammals, which, thanks to their warm-bloodedness and highly developed brain, turned out to be better adapted to these external phenomena and emerged victorious in the struggle of life.
Literature
1. Vorontsova M. A., Liozner L. D., Markelova I. V., Puhelskaya E. Ch. Triton and axolotl. M., 1952.
2. Gurtovoy N. N., Matveev B. S., Dzerzhinsky F. Ya. Practical zootomy of vertebrates.
3. Amphibians, reptiles. M., 1978. Terentyev P.V. Frog. M., 1950.
About 300 million years ago, the first amphibians appeared on Earth. However, already at the end of this period and beyond, the climate became dry again, and the descendants of the first amphibians began to develop in two directions. Some remained near the water and turned into modern amphibians. Others, on the contrary, began to adapt to the dry climate and turned into reptiles.
What changes have they made? First of all, a dense shell appeared on the eggs, so that they could be laid on land. In addition, reptiles began to lay large eggs, with big amount yolk. The development of the embryo lengthened, but what began to hatch was not a helpless larva, but a fully formed animal, differing from an adult only in its smaller size, already fully adapted to living conditions on land.
Adult reptiles also acquired the changes necessary for life on land. They have developed dense, keratinized skin that prevents evaporation. Oxygen does not pass through such skin. Therefore, the lungs have changed: they have acquired a cellular structure, that is, their working surface has greatly increased. In addition, ribs appeared, a rib cage was formed, and the breathing process became active through expansion and contraction chest. A septum has appeared in the ventricle of the heart, although it is not completely complete, so that part of the blood mixes in it. The separation of venous and arterial blood in reptiles is much more perfect than in amphibians. However, they remain cold-blooded animals, their body temperature depends on the ambient temperature.
In the skeleton, along with the appearance of ribs, the cervical region and the head became more mobile. When grasping prey, reptiles do not turn their whole body, as fish and amphibians do, but only turn their head. The senses have also improved. Of particular note is the improvement of the brain. Due to more varied movements, the cerebellum, which is responsible for the coordination of movements, has enlarged. More complex structure have a brain and sensory organs, as well as the behavior of reptiles compared to amphibians.
The rise and extinction of ancient reptiles
So, reptiles became much more active and, not afraid to move away from the water, spread widely across the Earth. Gradually, many species emerged among them. The appearance of giant reptiles is especially characteristic of this time. Thus, some dinosaurs (“terrible lizards”) were up to 30 meters long and weighing up to 50 tons - the largest terrestrial vertebrates that ever existed on Earth. Such giants were even forced to return to a semi-aquatic lifestyle again - their mass decreases in water. They roamed shallow waters and fed on coastal and aquatic plants, reaching them with their long necks. There were also predators then, also very large, up to 10 meters long. Some reptiles that lived at that time even completely returned to an aquatic lifestyle, although they did not lose pulmonary respiration. Such, for example, was an ichthyosaur, or fish lizard, very similar in shape to a modern dolphin. Finally, there were flying lizards - pterodactyls.
Thus, reptiles have mastered all habitats - land, water and air. They formed many species and became the dominant animals on Earth.
But 70-90 million years ago, the climate on most of the Earth changed dramatically and became cold. At the same time, there has become more diverse species of warm-blooded mammals - competitors of reptiles. This led to the fact that most reptiles, primarily all giant forms, became extinct, since giants cannot hide in shelters for the winter. Few reptiles have survived to this day - turtles, crocodiles, lizards and snakes. By the way, among them the largest are found only in warm countries and lead an aquatic or semi-aquatic lifestyle.
Two hundred million years ago, the rulers of our planet were the ancients - the crown of creation of that time! No other class of animal has held “power” for as long as the reptiles.
There were many of them - ancient lizards, crocodiles, tuataria, but the pinnacle of their development was, naturally, dinosaurs. Beastly lizards lived everywhere: on land, in water, in the air!
Dinosaur Science
Ancient reptiles left behind many mysteries that not everyone can solve. Using the remains of the bones of lizard animals, with the right approach, you can “draw” a picture of the past: the external characteristics of the lizard, its way of life, and so on. This is what paleontologists do. Their work is somewhat reminiscent of the work of detectives: from broken fragments they have to reconstruct the entire period of the life of a giant reptile! Here you need to be able to competently combine your intuition with logic and imagination, collecting the smallest fragments " past life"of this or that dinosaur.
Restoring paintings from the past is not an easy task. You can’t do without fantasy and a well-developed consistent imagination. Paleontology is, to some extent, a creative science: even a seemingly insignificant fact, if properly substantiated, can play an important role in the chain of events of that era... The Age of Dinosaurs!
A little classification
Reptiles are a rather peculiar group of living beings. The fact is that this class is divided into subclasses, the most primitive and ancient of which are the so-called anapsids. The last of them died out two hundred million years ago. A separate branch of this group is synapsids. These are already the ancestors. The synapsids themselves did not live to see the heyday of their descendants. Even later, a branch of diapsids appeared, which in turn divided into lepidosaurs and archosaurs. The first include both lizards, snakes, and tuataria living in our time, as well as some extinct ones. sea predators with long and snake-like necks called plesiosaurs. Archosaurs include crocodiles, pterosaurs and dinosaurs. These ancient reptiles are almost all extinct. Only crocodiles remained. Are they really the only descendants of ancient reptiles? Not certainly in that way!
Feathered Legacy
The direct descendants of dinosaurs are birds. Although this is not the class Reptiles, it is precisely feathered due to its structure and appearance resemble ancient lizards. At the same time, feel the difference: birds are descendants of animal lizards such as the pterosaur Quetzalcoatlus, namely “terrestrial” dinosaurs! died out without leaving a legacy.
Death of a dynasty
Ancient reptiles were very diverse and numerous, in their perfection and organization no other could compare with them. Animal lizards were studied and continue to be studied with greater interest than others. The collapse of the “dinosaur empire” still gives rise to a lot of theories, disputes, and versions. For whatever reason, the death of the dynasty of reptiles ruling the world occurred, several million years passed before the Earth was able to recover from the global catastrophe. When this did happen, the giant dinosaurs no longer had a place on it. They are extinct forever. Instead, others appeared - beautiful and strong animals! But you and I already know that one small group of descendants of ancient reptiles still managed to survive, and today its representatives are all around us... These are birds!
Modern reptiles evolved from ancient amphibians - stegocephali who lived in the middle Paleozoic era. The most ancient of reptiles are considered cotylosaurs, who lived 230 - 250 million years ago. Some features of their organization are preserved in the appearance of turtles.
The heyday of reptiles was the Mesozoic era (250-65 million years ago). In those ancient times, they lived on land and in water, and flew in the air (picture).
Flying pterodactyls, rhamphorhynchus, pteranodons they looked like giant bats. Their wingspan reached 10-12 m. Lizards resembling dolphins and seals lived in the water. These were ichthyosaurs, plesiosaurs. These groups of ancient reptiles became extinct, leaving no descendants behind.
Among the ancient lizards there were two more groups who played important role in the appearance of birds and mammals: dinosaurs And animal-like reptiles.
Dinosaurs were a very diverse group: peaceful (herbivorous) and ferocious predators. Some moved on four legs, others moved only on two hind legs and stood upright. Famous and very large dinosaurs- more than 30 m long, and small ones - the size of a small lizard. The largest are considered diplodocus(27 m long and weighing about 10 tons), Apatosaurus, Brachiosaurus, Seismosaurus. They lived near bodies of water and stood in the water for a long time, eating aquatic and semi-aquatic vegetation. There were dinosaurs with ridges on their backs, which they used to capture solar energy. Scientists suggest that birds originated from one of the groups of dinosaurs. The resemblance to dinosaurs is especially noticeable in the appearance of the first bird - Archeopteryx.
Beast-like reptiles were named so for their resemblance to animals. Unlike lizards, their legs were located under the body, lifting it above the ground. Fangs stood out among their teeth, fleshy lips appeared on the front of their heads, skin probably had glands.
However, throughout the Mesozoic era, the fate of dinosaurs and beast-like reptiles was different. Dinosaurs were favored by the warm, mild climate of this era, and they dominated everywhere. The beast-like creatures were few in number and invisible. At the end of the Mesozoic era, the ratio of species numbers began to change in favor of animal-like animals.
The extinction of dinosaurs occurred as the planet's climate changed, since at the end of the Mesozoic the long warm period was replaced by low temperatures. At this time, vegetation began to change, and with the beginning of the Cenozoic era, angiosperms began to spread on Earth.
There are many scientifically proven (mountain building and climate change) and alleged reasons for the extinction of dinosaurs. It is possible that a large asteroid passed near the Earth, influencing climate change and the natural environment surrounding dinosaurs.
Did the ancient lizards disappear from the face of the planet without a trace, leaving only monuments in the form of skeletons and prints? In the modern fauna of reptiles there are tuateria, which is called a living fossil. There is a lot that is archaic in the appearance of this animal: the remains of a shell on the body, the primitive structure of the spine, an additional eye in the parietal part of the head. This reptile lives on small islands off New Zealand and is strictly protected as a living natural monument. Turtles are close to their Mesozoic ancestors.
In some organizational features, crocodiles are close to dinosaurs. Lizards and snakes share some similarities with dinosaurs. But in the history of the Earth's vertebrate fauna, they appeared only in the Cenozoic era, when their related groups lost their former greatness.
Reptiles or reptiles– lat. Reptilia, the first class of terrestrial vertebrates that have inhabited our planet for many years. Primary or ancient reptiles arose from ancient amphibians, and climate change contributed to this. IN ancient era The climate on the planet gradually became drier and colder, as a result, water bodies began to dry up, large wetlands turned into huge dried “craters”, etc. Change climatic conditions began to occur due to colossal mountain-building processes.
At this time, most of the ancient amphibians became extinct, due to the presence of thin and bare skin, poorly developed internal organs and so on. In the rest of the animals, the skin gradually began to horny and harden, the structure of the lungs became more improved, as a result, the ability to better absorb oxygen appeared, the brain of the animals changed, and also the appearance of new way reproduction - laying hard-shelled eggs. This is how the primary or ancient reptiles arose.
The primary reptiles that appeared in the ancient era began to develop quite quickly, as a result of which the ancient amphibians were relegated to the background. In the Middle or Mesozoic era, this development reached its maximum peak, and it was then that vertebrate animals of enormous size began to appear, called ancient reptiles. They filled the entire territory of the planet and gained a dominant position on land, in water and in the air.
The most common species among ancient reptiles or reptiles are:
Squad of crocodiles- predatory vertebrates, only 22 species of crocodiles are now registered.