For Paleozoic era followed by one of the most remarkable periods in the history of life on Earth - the reign of the Mesozoic reptiles. During the Mesozoic, over a period of 190 million years, there was an astonishing expansion of reptiles. Reptiles, which evolved in the Late Carboniferous, took advantage of amniotic egg reproduction to spread across land, colonize the seas, and take to the air using newly developed wings. One of the branches of reptiles gave rise to birds that competed with the flying reptiles themselves. The other branch, as we have already seen, developed into the mammalian branch. Yet the most striking characters in the reptile drama are dinosaurs. They and all their relatives, swimming and flying, became extinct in the Mesozoic era. They became completely extinct, down to the last individual, leaving new groups of animals, mainly descendants of Mesozoic mammals, to populate the Earth.

The fossil record shows the existence of hundreds of genera of dinosaurs ranging in size from a chicken to tens of meters in size, with dozens of diverse adaptations to life in different conditions. Yet, like all other reptiles, all dinosaurs were probably cold-blooded and dependent directly or indirectly on the abundance of leafy vegetation. However, dinosaur fossils have been found on every continent except Antarctica. From this circumstance we can conclude that in Mesozoic times lowlands with a mild climate and lush vegetation were widespread, since animals like dinosaurs could not exist in high mountains with steep slopes and in a cold climate. This conclusion seems to be consistent with the data we have on plate movements earth's crust. Looking again at Figure 27, we see that most of the land area that is now located in the middle or high latitudes was (presumably) at lower latitudes in the middle of the Mesozoic. It is possible that the southern part North America and the southern part of Europe were then adjacent to the equator. If the continents occupied the same position in the Mesozoic as they do now, it is unlikely that reptiles would have been so numerous and reached such enormous sizes.

With the help of the map presented in Figure 38, we can explain the rise of Mesozoic reptiles from a different point of view. By the end of the Mesozoic, the territory of North America, compared to the present time, was more occupied by shallow seas and to a lesser extent by land, mostly low-lying, and the Gulf of Mexico was connected to the North Arctic Ocean. Under these conditions, the climate of the central and northern parts of the continent may have been milder than it is now, especially in winter. In Europe and other continents, vast seas were common in the Mesozoic.

Thus, the flowering of reptiles in the Mesozoic era, which at first glance seems inexplicable, is ultimately satisfactorily explained by the presence of environmental conditions that were favorable to cold-blooded animals. Thus, as when considering the earlier stages of the history of living beings, we are once again convinced that environmental conditions have a decisive influence on the development of the animal world through natural selection.

Types of dinosaurs

We have already said that there were several hundred species of dinosaurs. But they all belonged to two distinct divisions that descended from a common ancestor in Triassic time, before dinosaurs as such appeared. The name "dinosaur" is more popular than scientific. It means "terrible lizard" and when it was first introduced it referred to very large and ferocious animals. But dinosaurs of this type were relatively few among the many reptiles that we currently classify as dinosaurs. This group includes a large number of reptiles that possessed neither ferocity nor large sizes.

Scientists distinguish the two main divisions of dinosaurs mentioned on the basis of the structure of their pelvic bones. One group included dinosaurs whose pelvic bones had the same structure as those of lizards, and the second group included dinosaurs whose pelvic bones resembled those of birds. This important design difference in the device is shown in Figure 46. There is no need to dwell on this in more detail, we are primarily interested in appearance and the lifestyle of dinosaurs. Therefore, we can move on to describing some of the most prominent representatives world of dinosaurs. Triassic dinosaurs were quite primitive and had modest sizes. All of them rested on their hind legs, and the front legs, much smaller in size, did not reach the ground (Fig. 47). Their necks were much longer than those of the Permian crawling reptiles. However, although dinosaurs became bipedal, they did not stand upright like a bipedal human. When they walked or ran, their bodies occupied a position closer to horizontal than to vertical, although, undoubtedly, they could sometimes straighten up, as squirrels often do. As for the legs of dinosaurs, by looking at the traces they left on wet sand and silt (photo 18), on which the prints of three or four long fingers and another short, additional one, only occasionally touching the ground are clearly visible, we can understand why the first the researchers of these tracks took them for the tracks of birds.

Rice. 46. ​​Connections between dinosaur groups mentioned in the book

Most dinosaurs were carnivores, like their Permian ancestors; the presence among the Triassic fossil species that had unusual types of armor, projections and spines suggests that they were already beginning to “take” protective measures against their enemies - others predatory dinosaurs.

Rice. 47. Coelophysis, a typical Triassic dinosaur. It is very likely that the small footprints shown in photo 17 were left by this particular dinosaur

Naturally, this group of rather primitive Triassic dinosaurs included the ancestors of all later dinosaurs. It is best to subdivide them according to the method of nutrition, lifestyle and structural features. We can distinguish between herbivorous and carnivorous, bipedal and quadrupedal dinosaurs, as well as dinosaurs that had armor, bone plates or protective horns, and those that did not have these devices. We will divide the lizards we are considering into four large groups.

Herbivorous bipeds. Although almost all early Mesozoic dinosaurs were predators, many herbivorous individuals were found among their descendants. Judging by the tracks they left, they quite often moved on four legs. Among them, the common one was the iguanodon (Fig. 48), a densely built animal that reached about 11 meters in length. In one place, more than 20 skeletons were found completely intact; based on the skeletons of turtles, crocodiles and fish found with them, one can think that these dinosaurs lived in swamps. Their “hands” had five fingers, and the “thumb” finger was a large sharp spike, which probably served as a good weapon of defense. Apparently, these lizards fed by bending tree branches with their forelimbs and eating shoots. Their tracks show that they moved at a walk and probably not very quickly, only occasionally making short jumps.

Rice. 48. Iguanodon, a large bipedal herbivorous dinosaur that lived in Europe

Another group of herbivorous bipedal lizards, reaching 6-12 meters in length and called hadrosaurs, resembled amphibians in their lifestyle and lived in swamps or on their marshy shores (photo 43). They had small membranes between their toes, and their tail was thin, like that of crocodiles, and acted like an oar when moving in the water. The nostrils were positioned so that almost the entire body could be submerged in water. The mouth consisted of a horny beak, similar to a duck's. The jaw contained up to a thousand teeth, long, very thin, located close to each other. When the horny beak removed soft plants from the swamp, the upper and lower jaws, on which the teeth grew, began to move back and forth and rub against each other like two wire brushes, thus grinding the food.

Photo 43. Hadrosaurs (1), an "armoured" ankylosaur-like dinosaur (2) and carnivorous dinosaur Struthiomimus (3). The tree on the left is an angiosperm. Reconstruction

Carnivorous bipeds. Where herbivorous animals are found, there are always predators that hunt them. Among the dinosaurs there were many predators of various sizes and shapes running on two legs. One of them, Ornitholestes, only about two meters long, had such an “elegant” structure that it supposedly weighed less than 25 kilograms. It was an active animal, adapted to fast running; grasping forelimbs with three very long fingers could catch even a very small lizard that was trying to escape. Another dinosaur, Struthiomimus (photo 43, number three), was slightly larger and resembled an ostrich. It even had a toothless beak. The crushed skull of a related dinosaur was found in a fossil nest containing dinosaur eggs. This circumstance, as well as the general appearance of the animal, which had light weight and flexible “arms,” leads us to the conclusion that Struthiomimus fed on eggs and robbed nests.

Another dinosaur, Deinonychus, about 2.5 meters long, which may have been a descendant of the dinosaur Ornitholestes, was distinguished by two very interesting adaptations that allowed it to lead a predatory lifestyle. The second toe on each hind foot was equipped with a claw, much longer and sharper than all the other claws. This finger had a special joint that allowed it to rise above the ground and rotate 180° (Fig. 49), which allowed the reptile to strike its prey swipe kick, a blow that could rip open the belly of an animal the same size as the predator itself. In addition, this dinosaur's long tail contained tendons that could instantly "fuse" bones together, turning the tail into a rigid counterweight to the entire body. Possessing similar claws and tail, such a dinosaur; must have been a very active and dangerous animal.

Rice. 49. Deinonychus, a predator armed with sharp claws

Some bipedal predators were much larger, exceeding 9 meters in length. One of them, Tyrannosaurus Rex, was the largest known land predator; it had a length of up to 15 meters, a height of up to 6 meters and supposedly weighed 7-8 tons (photo 44). The length of its skull was 1-2 meters, and in its mouth there were many sharp jagged teeth fifteen centimeters long. Since its forelimbs were very short, it apparently did not use them when attacking and eating prey. Tyrannosaurus's main prey were herbivorous dinosaurs, such as hadrosaurs and dinosaurs armed with horns.

Photo 44. Tyrannosaurus, the largest predator, attacks a Triceratops, which has prepared to defend itself. The head of a Triceratops is covered with an armored helmet. The trees are palm trees, which are classified as angiosperms. Reconstruction

Amphibian tetrapods. Let's move on to giant dinosaurs, which are so often described in popular literature that their appearance is familiar not only to scientists. The fossil record contains evidence of at least four different genera that are very similar in appearance; we will mention only two of them. At first glance it may seem strange that although dinosaurs from these two genera were quadrupeds, their front legs were much shorter than their hind legs. But in reality this was to be expected, because they were descendants of Triassic bipedal dinosaurs with short forelimbs. Perhaps the best known is the genus Apatosaurus (photo 45) - huge, sedentary herbivores that reached 23 meters in length; their short body was supported by massive column-shaped legs equipped with claws. In front was a long flexible neck with a small head, which was balanced at the back of the body by a long flexible tail, tapering towards the end. The animal must have weighed more than 30 tons, that is, four or five times more than the largest African elephant.

Photo 45. Apatosaurus, a four-legged amphibian-like dinosaur, more than 20 m long, on the shore of a Jurassic pond. Two other similar dinosaurs are grazing in the water. Compared to them, the crocodile in the foreground looks very small. The vegetation consists of cycads and horsetails. Reconstruction

As the size and weight of the ancestors of this dinosaur increased, the skeleton evolved to reduce its weight by forming cavities and holes in the vertebrae; thus weight was reduced where loads were light and maintained where strength was important, such as columnar legs. The footprint of this dinosaur, left in the Mesozoic silts, exceeds 90 centimeters in length.

Another giant dinosaur, Diplodocus, was also a herbivore, similar in many respects to the one described above. The main difference from it was that Diplodocus was somewhat longer (the length of one specimen, according to calculations, exceeded 29 meters with a height of almost 14 meters), but not so massive, its weight was supposedly 10-12 tons. Without a doubt, these giants spent most of their time in swamps and rivers, eating soft plants. Away from the coast, among the marshy islands, they were safer from large predators; therefore, such places were not only a “dining room” for them, but also a refuge. For even greater safety, the nostrils of these giants were placed on the very top of their heads, which allowed them to breathe calmly, almost completely immersed in water and thus out of sight of their enemies. These and some other dinosaurs swallowed their plant food whole and ground it up after it entered their stomach. Like chickens, which usually have a lot of pebbles in their crops, dinosaurs swallowed stones the size of potatoes and used these tools to crush food with their strong stomach muscles. Sometimes piles of such stones, once rounded and polished in the stomachs of dinosaurs, are found along with their skeletons, and they are located where the belly of a large dinosaur was.

These huge animals probably laid eggs, although this has not yet been confirmed by finds; the eggs died in the water, so they had to lay them on land, and maybe on islands or other places where it was difficult for predators to penetrate.

Huge, four-legged, amphibian-like dinosaurs had even smaller brains relative to their body weight than other dinosaurs, although this group was not particularly famous for its mental abilities. In Diplodocus, the true brain weighed only about seven grams per ton of body weight. We say "true brain" because Diplodocus, like many other dinosaurs, had an additional, much larger coordinating center located in the spine, near the pelvis. This center connected to the true brain through the spinal cord and controlled the movement of the hind legs and tail. Although such a device may seem inconvenient, we must admit that it worked "properly" because many people possessed it. various types dinosaurs that lived for tens of millions of years. This, of course, was facilitated by the habitat of dinosaurs with a mild climate and little change. natural conditions; in such an environment there were almost no problems requiring mental effort.

Quadrupeds equipped with armor or horns. Our list of diverse dinosaurs also includes a fairly diverse group of species that, while not closely related, had unusual armor, or horns, or both. Despite the fact that their Triassic ancestors were bipedal, these dinosaurs again descended on all four limbs. Yet their front legs were still shorter than their hind legs, like Apatosaurus. Being herbivores, they needed protection from predatory reptiles; this caused the development of armor and protective horns.

The most prominent of these armored reptiles was the Stegosaurus. Its skeleton, about 6 meters long and believed to weigh 4 tons, shows thick triangular bone plates bordering the spinal ridge, to which they were probably connected by ligaments. Perhaps these plates, the largest of which reached a size of 75 centimeters, protected the spine from bipedal predators, who, when attacked, probably tried to grab the scruff of the neck, as a terrier does when killing a rat. In addition, the stegosaurus was armed with a pair of strong, thick spines about 60 centimeters long, located at the end of its tail. One blow from such a tail could probably knock down a fairly large opponent and also cause him serious damage.

Ankylosaurus and its relatives (photo 43) probably had the same protection as modern armadillos. Reaching 6 meters in length and 2.5 meters in width, they had a height of less than 1.5 meters. Behind a powerful, thick skull equipped with a beak, the entire upper half of their body was covered with heavy bony plates. Some of them also had huge spikes along their entire body, from the shoulders to the tail, which resembled a heavy shovel or club. With such protective armor, these reptiles probably moved slowly. But when danger approached, they could press themselves to the ground, tucking their paws under them, and defend themselves from attack by striking with their tail.

In another way, using horns, Triceratops and its many relatives defended themselves (photo 44). These bulky, short-tailed quadrupeds reached 7.5 meters in length and three meters in height. Their most characteristic feature was a huge, heavy skull that extended back like a large shield to protect the neck. The front of the skull was equipped with two horns protruding above a narrow beak, similar to the beak of a parrot. Inside the skull was a brain, small in our opinion, but large enough for a dinosaur. The presence of such a brain suggests that these animals, which had a protective helmet and horns, were quite mobile. This is evidenced by the insecurity of the back of their body, which had neither armor nor any weapons. It is clear that they could quickly turn to repel an enemy attack with their horns. Traces of such ancient battles are perhaps the scars often found on the fossil remains of neck armor.

When we talk about battles between dinosaurs, we can't help but wonder whether they took place in silence or were accompanied by loud screams, as is the case with fights between modern cats and dogs. Dinosaur anatomy experts can tell us what little is known on the subject. It appears that the configuration of the small bones at the base of dinosaur tongues is similar to that of some living animal species. Based on this analogy, it can be assumed that at least some dinosaurs could make croaking or barking sounds, like modern crocodiles do. Therefore, if in the Paleozoic there was most likely silence on land, broken only by the noise of the wind, streams and surf, then the Mesozoic landscapes could already be enlivened by the sounds that animals made.

Protoceratops, related to Triceratops, but less complexly organized, a small dinosaur with a beak but without horns, who lived in Asia, became widely known in connection with the discovery of its eggs and nests by a paleontological expedition in Mongolia in the twenties of our century. In the late Mesozoic, the area was as dry as it is now, and eggs were laid in small depressions in the sand, which has now turned into sandstone. Female dinosaurs dug holes and laid up to 15 eggs 15-20 centimeters long in them. Several such nests have been found, and at least two of the eggs were found to contain tiny bones of baby dinosaurs that failed to hatch. Eggs of other types of dinosaurs, both larger and smaller, were also found.

Marine reptiles

When studying life in the Mesozoic, perhaps the most striking thing is that almost half of all known species reptiles lived not on land, but in water, in rivers, estuaries and even in the sea. We have already noted that in the Mesozoic, shallow seas became widespread on the continents, so there was no shortage of living space for aquatic animals.

In the Mesozoic layers there are a large number of fossil reptiles adapted for life in water. This fact can only mean that some reptiles returned back to the sea, to their homeland, where the ancestors of dinosaurs - fish - appeared long ago. This fact requires some explanation, since at first glance there was a regression here. But we cannot consider the return of reptiles to the sea to be a step backward from an evolutionary point of view simply on the grounds that Devonian fish came out of the sea onto land and developed into reptiles after passing through the amphibian stage. On the contrary, this position illustrates the principle according to which each actively developing group of organisms strives to occupy all varieties of the environment in which it can exist. In fact, the movement of reptiles into the sea is not very different from the colonization of rivers and lakes by amphibians in the Late Carboniferous (photo 38). There was food in the water and the competition was not too fierce, so first amphibians and then reptiles moved into the water. Already before the end of the Paleozoic, some reptiles became aquatic inhabitants and began to adapt to a new way of life. This adaptation went mainly along the path of improving the method of movement in aquatic environment. Of course, reptiles continued to breathe air in the same way that a modern whale, a mammal, although similar in body shape to a fish, breathes air. Moreover, Mesozoic marine reptiles did not evolve from any one land reptile that decided to move back into the water. Fossil skeletons provide undeniable evidence that they had different ancestors and appeared in different times. Thus, fossil remains show how diverse the response of organisms was to changing environmental conditions, as a result of which a vast space was created, abundant in food and suitable for settlement.

Extensive information has been obtained from the study of fossil remains contained in marine mudstones and chalk limestones; These fine clastic rocks preserve not only bones, but also imprints of skin and scales. With the exception of the smallest and most primitive species, most marine reptiles were predators and belonged to three main groups: thyosaurs, plesiosaurs and mosasaurs. Briefly characterizing them, we must first note that ichthyosaurs acquired an elongated shape similar to fish (Fig. 50) and were excellently adapted to fast swimming in pursuit of fish or cephalopods. These animals, reaching 9 meters in length, had bare skin, a dorsal fin and a tail like a fish, and their four limbs turned into a kind of seal flippers and were used to control the movement of the body when swimming. All the fingers in these flippers were closely connected, and there were additional bones in them to increase strength. The large eyes of ichthyosaurs were adapted to see well in water. They even had one very significant improvement in the reproduction process. Being animals that breathed air but lived in sea ​​water, they could not lay eggs. Therefore, ichthyosaurs developed a method of reproduction in which the embryo developed inside the mother’s body and, upon reaching maturity, was born alive. They became viviparous. This fact is established by the discovery of perfectly preserved remains of female ichthyosaurs with fully formed young inside their bodies, the number of young reaches seven.

Rice. 50. Four groups of animals that acquired a streamlined body shape as a result of adaptation to life in water: A. reptile, B. fish, C. bird, D. mammal. Initially they had different appearances, but in the course of evolution they acquired external similarities

The second group includes plesiosaurs, which, unlike the fish-like ichthyosaurs, retained the original body shape of reptiles, reaching 7.5-12 meters in length. If not for the tail, the plesiosaur would have looked like a giant swan. Of course, the ancestor of the plesiosaur was not at all the same land reptile that gave rise to the ichthyosaurs. The legs of plesiosaurs turned into long fins, and the head, set on a long neck, was equipped with sharp teeth, which closed and reliably held the most slippery fish. Such teeth prevented chewing; The plesiosaur swallowed its prey whole and then crushed it in its stomach using pebbles. The diet of plesiosaurs can be judged from the stomach contents of one of them, which apparently died before the stones in its stomach had time to properly crush the food it swallowed. It was found that the bones and fragments of shells contained in the stomach belonged to fish, flying reptiles and cephalopods, which were swallowed whole, along with the shell.

The third group of marine reptiles was called mosasaurs because they were first discovered near the Moselle River, in northeastern France. They could be called “belated” because they appeared only in the Late Cretaceous, when ichthyosaurs had been populating the seas for almost 150 million years. The ancestors of mosasaurs were lizards rather than dinosaurs. Their length reached 9 meters, they had scaly skin, and their jaws were designed in such a way that they could open their mouths wide, like snakes.

A streamlined body as an adaptation to living conditions in an aquatic environment is found not only in ichthyosaurs and mosasaurs. The same can be seen in a number of animals that lived before and after the Mesozoic, and in the Mesozoic (Fig. 50).

Reptiles in the air

The story of the rise of reptiles in the Mesozoic does not end with what is stated above. Reptiles not only spread across the land and filled the seas, they also took to the air, following two lines of evolution at once. They learned to fly like reptiles, and in addition, moving along a completely different path of development, they learned to fly like birds. As far as can be judged from fossil remains, true flying reptiles were not as numerous as sea reptiles. However, they were the first animals to take to the air after insects, who did so back in Devonian times. Naturally, the air environment is more difficult to conquer and more dangerous than the sea. Moving in the air, or even floating passively, requires more specialized equipment, more energy, and more skill (by which we mean agility and quick response) than moving in water. This is basically why man built ships long before airplanes. The interval between these human inventions was about several thousand years. And between the emergence of reptiles in the Late Carboniferous and their penetration into the air (Jurassic time), about 80 million years passed.

We know a lot about the structure and appearance of flying reptiles thanks to the fact that in the southern part of Germany [Germany, Bavaria. - Ed.] sedimentary rocks of an unusual type are widespread. These rocks are layers of limestone of Late Jurassic age, so fine-grained that it was used to engrave illustrations for books (before steel and copper plates were used for this purpose) and for this reason received the name lithograph stone. The unusually fine-grained composition of these limestones suggests that they were deposited in shallow lagoons, protected from the swell of the open sea by sand bars or coral reefs. Loose sediments at the bottom of the lagoons retained imprints of even the smallest details of plants or animal bodies, which sank to the bottom and were covered with silt. As a result, lithographic stone is famous for the fossil remains of plants, invertebrates, fish and reptiles it contains.

Photo 46 Skeleton of Rhamphorhynchus, a primitive flying reptile, found in lithographic limestones in Germany

Many winged reptiles were found in these deposits, and similar remains were found in other Mesozoic layers in various places. Examining the remains of one of the Jurassic primitive reptiles, preserved to the smallest detail (photo 46), we see that its body adapted to flight in the following way: 1) weight decreased; 2) “devices” for flight control appeared; 3) a mechanism for flight was created. Here are some of these devices:

1. Small body size; Although some flying reptiles were as large as turkeys, others were no larger than canaries. The skeleton was lightened due to the development of thin, hollow bones of the wings, and in some species the skull had an almost reticular structure and consisted of thin bones.

2. The eyes and the part of the brain that controls vision were unusually well developed.

3. The most remarkable feature were the wings. Looking at Figures 51 and 52, we can easily imagine that the fourth finger on the forelimb, the word “little finger,” was unusually elongated in relation to the others. From the tip of this toe to the hind leg and further to the tail, a thin membrane of skin stretched, forming a wing.

Rice. 51. Pteranodon, a flying reptile with a growth on its skull; he flew vast distances over the vast Cretaceous seas in what is now the states of Kansas and Nebraska

All these three groups of devices taken together created a device that, although clumsy, could fly. The formation of the wing, accompanied by improvements in the eye and a decrease in overall weight, made flight possible and resulted in amazing body proportions. For example, one of the flying reptiles with a wingspan of 90 centimeters, according to calculations, during life weighed less than 450 grams. The skin of such reptiles was bare, and the jaws were equipped with numerous sharp teeth, common to reptiles. These animals probably hovered rather than flew, like modern buzzards. Descended from terrestrial predators, they apparently remained carnivores and, slowly gliding over the water, looked out for sea animals or large insects. Their skeletal structure shows that they could not walk. Obviously, they did not land on the surface of the earth, but on tree branches or rock ledges on which they hung, like modern bats.

Rice. 52. Scheme of comparison of the wing of a flying reptile, bat and bird. All these wings appeared at different times. In a reptile, the entire wing is supported by only one finger. The bat's outer wing is reinforced with four fingers. In a bird, most of the wing is supported by the bones of the shoulder and forearm, and the load-bearing surface is formed by light, hard feathers. Of all three types, this wing is most suitable for its purpose.

Later, the development of flying reptiles, the remains of which were found in the sediments of shallow seas of the Cretaceous time, followed the path of replacing teeth with a long beak, which, of course, better suited their lifestyle. In one of the genera, a special protrusion, or crest, appeared in the back of the skull (Fig. 51), which may have balanced the long beak and made it easier for the reptile to maneuver in the wind. But the main change concerned the increase in wing area, apparently to better support the body in the air. One of the flying reptiles had wings with a span of 7.5 meters to support its body, which supposedly weighed less than 12 kilograms. Such a wingspan allows us to consider these reptiles the largest flying animals in the entire history of life on Earth. Although flying reptiles were fragile until the end of their heyday, they survived for more than 100 million years.

But despite the fact that the wing of reptiles performed its functions and existed for a long time, it was a less successful adaptation for flight than the wing of birds that appeared independently of it and later of mammals - bats. Figure 52 shows all three wings, and, as can be seen, the bird's wing is the most perfect of them all.

Birds

In the Jurassic time, reptiles living along the shores warm seas, there were different types of flight. We have already seen that several species of terrestrial reptiles took to the air using the leathery wings just described. But one species went even further. In one of the quarries during the development of lithographic stone in the middle of the 19th century. a fossil skeleton of a reptile was found, no larger than a crow, which had big eyes, teeth like reptiles, and fingers with claws on the forelimbs. It is amazing that very clear imprints of feathers were discovered, attached to the forearm and to the vertebrae long tail. It was undoubtedly a bird. It received the generic name Archaeopteyx ("ancient wing") and the species name Uthographica after the name of the rock (photo 47). Two more fossil skeletons and a separate feather imprint were discovered in the same layer.

Photo 47. Archaeopteryx, the oldest bird known to us, sits on a coniferous tree branch, about to eat a captured lizard. In the foreground on the right are cycad plants; behind there are coniferous trees and another similar bird. Reconstruction

Of course, these finds were of extraordinary interest and therefore were carefully studied. The results of the research can obviously be summarized as follows: Archeopteryx, in its main features, is a flying reptile, but since, by definition, birds have feathers, but reptiles do not, it can be classified as a bird. The structural features of Archeopteryx allow us to confidently say that this oldest bird known to us descended from a bipedal reptile that lived on earth. The presence of feathers strongly suggests that she had warm blood, because one of the main functions of feathers is thermal insulation. Many birds have blood that is even warmer than that of humans. Their feather cover and high motor activity allow them to maintain a normal body temperature of about 39.5 ° C.

Feathers are made of the same tough horny substance that makes up scales. Some scientists suggest that the small reptile that was the ancestor of these primitive birds had scales and that the scales first became wavy at the edges, perhaps because this shape protected the skin from overheating sun rays. The wavy edges were also useful in another way, as they reduced the body's loss of heat, and gradually these scales turned into feathers. The rigidity and light weight of the feathers made them ideal for flight.

Although the first bird had feathers, it, like its relatives - flying reptiles with leathery wings, did not fly well. Its structure indicates that the bird was probably well adapted to gliding flight. Perhaps she lived on land and, being a predator, fed either on small animals or carrion. The fact that its remains were found in marine limestones only indicates that individual specimens were carried out to sea by wind or current and buried in soft bottom mud. The fragile bodies of birds that died on land were simply not preserved.

By the Cretaceous period, the clumsiness of flight in birds disappeared and many of them acquired a beak instead of teeth. Some birds have adapted to life on the water. An example is the very loon-like swimming and diving bird Hesperornis (Fig. 50), which was about two meters long and still had teeth and wings, although not as strong and smaller than those of flying birds. The existence of birds that almost left air environment, moving on to swimming, indicates that in the early stages of development, birds hunted fish in the same way as reptiles have constantly done since the beginning of the Mesozoic era.

The end of the huge reptiles

The end of the Cretaceous period, which meant the end of the entire Mesozoic era, can be called a “crisis” in the history of the biosphere, because at this time the extinction of many groups of animals occurred. Reptiles suffered the most noticeable damage. All dinosaurs, all flying reptiles, and all marine reptiles, except sea turtles, became extinct; Only lizards, snakes and turtles survived and continued the line of reptiles. Most cephalopods have disappeared from invertebrates, including all belemnites, as well as some lineages of marine bivalves and snails.

The extinction was selective because mammals and land plants were little or not affected, but fish and many invertebrates survived completely. Therefore, attempts to attribute this extinction to any one cause have failed. Until the timing of major events in Earth's history was determined by radiometric dating, the end of the Mesozoic was commonly referred to as the time of the "great extinction." However, we now realize that this expression is not true. At least two circumstances indicate that the extinction did not have the nature of a catastrophe that destroyed all living things.

Firstly, it was selective, affecting some species and sparing others. Moreover, it was not limited to any one type of natural environment, encompassing land, sea and air. Secondly, although the extinction of species was most noticeable at the end of the Cretaceous, it took a significant period of time overall. In particular, different groups of reptiles went extinct at separate points throughout the Mesozoic. Therefore, whatever the cause of this phenomenon, it obviously did not cause a “sudden” extermination of species, at least in the sense of the word in which we apply it to events in the history of human society. Even the most dramatic extinction event, which occurred at the end of the Cretaceous, probably lasted several million years.

When we look at the geological record of what happened at the end of the Cretaceous, we see that the continents generally became taller. At the same time, and perhaps mainly as a result of this uplift, the areas of vast shallow seas on the continents were reduced and the swampy lowlands located along the shores of these seas disappeared. Temperatures have also dropped, partly due to rising and shrinking seas.

We must admit that the actual cause of the extinction has not yet been established. Previously advanced explanations—disease, lack of food, and the vaguest of all, “loss of vitality”—completely fail to explain why there was a selective extinction of some of the inhabitants of the land, sea, and air, rather than a complete extinction of the inhabitants of any one environment. It appears that the mammals emerged from this disaster unharmed.

It has recently been suggested that the end of the Mesozoic was marked by a series of reversals in the Earth's magnetic field (described in Chapter Six) and that these reversals may have affected the biosphere in some way, for example by changing the intensity of radiation reaching the planet. earth's surface. Objections have been raised against this, but it may be too early to assess the pros and cons. Suffice it to say that the extinction that marked the end of the “age of dinosaurs” still represents one of the greatest mysteries associated with the history of life on Earth.

Literature

Augusta Josef, Burian Zdenek. 1961, Prehistoric reptiles and birds: Paul Hamlyn, London.

Colbert E. H., 1951, The dinosaur book: NcGraw-Hill Book Co., Inc., New York.

Colbert. E.H., 1961, Dinosaurs. Their discovery and their world: E. P. Dutton & Co.. Inc., New York.

Fenton C.L., Fenton M.A., 1958, The fossil book: Doubleday & Co.. New York, p. 329-374.

Kurten Bjorn, 1968, The age of the dinosaurs: Weidenfeld and Nicolson, London. (Paperback.)

Swinton W. E., 1958, Fossil birds: British Museum (Natural History), London.

Swinton W. E.. 1970, The dinosaurs: Wiley-Interscience, New York.

The Volga region preserves the remains of giants who roamed the seas during the time of dinosaurs.

Early on an August morning in 1927, on the outskirts of Penza, not far from the ancient Mironositsky cemetery, a man appeared with a duffel bag over his shoulders - a political exile of modern times. Mikhail Vedenyapin. He went down into the Prolom ravine, to a small machine-gun firing range. There were no exercises that day, and in the ravine you could only meet boys running to collect shell casings.

Mikhail Vedenyapin had been living in Penza for two years, in exile. Before that, the tsarist courts exiled him, Admiral Kolchak promised to shoot him, and now the Bolsheviks did not like his views. And so the former professional revolutionary Socialist Revolutionary works as a statistician, in his spare time he writes notes in the magazine “Katorga and Exile” and wanders around the surrounding area in search of fossils. Like many scientists and simply curious people of those times, he has ten years left to live...

He walked along the slope of a deep ravine, picking up shells of mollusks from the ground that lived in a sea that had long ago disappeared - more than 80 million years ago. In one place, a sandy slope was broken by a machine-gun burst, and fragments of bones lay in the scree. The local historian collected them and climbed onto the cliff to see where it all fell out. It didn’t take long to search: huge bones were sticking out of the sand.

Vedenyapin immediately went to local history museum. Alas, the geologist was away; the rest of the staff listened to the news without interest. Then the former Social Revolutionary gathered his friends and began excavations. However, the bones lay at a depth of seven meters - the excavation needed to be expanded. This required diggers, and for them - a salary. Vedenyapin turned to the authorities for help. The provincial executive committee met him halfway and gave him a hundred rubles. From funds intended for the improvement of the city.

Modern dinosaur museum in the village of Undory (Ulyanovsk region). Many plesiosaur bones have been found in local shale mines.

A few days later, the slope of the ravine gaped like a huge hole, and strange rumors spread throughout Penza. Someone claimed that a mammoth's grave was found near the cemetery. Someone said that the exile was digging for an ancient sea frog. In one church, during the service, the priest even told the congregation about the stone bones left over from a gigantic beast that did not fit into Noah’s ark. Rumors fueled curiosity, and people crowded into the ravine every day.

In the confusion, a couple of bones were stolen, and Vedenyapin asked the police to send a security detail. It didn’t help: several more vertebrae disappeared during the night. Then a Red Army patrol was posted in the ravine. Soldiers with three-line rifles were on duty around the clock. The main Penza newspaper Trudovaya Pravda also reined in the hooligans: between articles about treacherous priests and where the butter and sugar had disappeared, a call appeared: “We kindly request those present not to interfere with the work and comply with the demands of those leading the excavations!”

When 30 cubic meters of rock were dumped into the dump, the lower jaw appeared - long, with crooked teeth. It became clear that the remains of a giant marine reptile were found in the ravine - mosasaurus. The jaw was outlined in a trench. It turned out to be a kind of table on which lay a rock-covered bone. They did not take it out for fear of breaking it, and they sent a telegram to the Academy of Sciences to send specialists.

Mosasaurus tooth from a private collection, Cretaceous layers of the Saratov region. Photo: Maxim Arkhangelsky

In early September, two preparators from the Russian Geological Committee arrived in Penza and, according to the newspaper, immediately “began work on exposing the mosasaurus and excavating it.” It was necessary to remove the bones before the slope floated away due to rains. And the shooting range had been idle for half a month. In a couple of days, the find was cleared of the rock. 19 large teeth, flattened on the sides, protruded from the jaw. Three more teeth lay nearby. There was nothing else.

The jaw was packed in a large box and taken out on a cart to be sent to Leningrad. A plaster copy was then donated to the regional museum. As it turned out, the remains belonged to a giant who lived at the end of the era of dinosaurs - the Hoffmann mosasaurus (Mosasaurus hoffmanni), one of the last sea lizards. Mosasaurs were real colossuses.

But they were not the only ones who lived in the Central Russian Sea, which existed in the territory Central Russia in the Mesozoic era. During the Jurassic and Cretaceous periods of this era, many dynasties of lizards were replaced. The bones of these leviathans are found not only in Penza, but also in the Moscow region, on the Kama and Vyatka, but most of them are in the Volga region - a giant cemetery of sea giants.

The sea came to the eastern edge of Europe about 170 million years ago, in the middle of the Jurassic period. “The general rise in sea levels during the Mesozoic era gradually led to the fact that the eastern part of Europe found itself under water. Then it was not yet a sea, but rather a bay, a long tentacle stretching from the south into the interior of the mainland. Later, the waves of the Boreal Sea moved from the north to the continent.

On the territory of the present Volga region, the bays met and formed a sea, which geologists called the Central Russian Sea,” says Mikhail Rogov, senior researcher at the Geological Institute of the Russian Academy of Sciences. The western coast of the Central Russian Sea passed where Voronezh now stands; in the east it was bordered by the islands of the Urals. Thousands of square kilometers went under water - from the future Orenburg steppes to Vologda and Naryan-Mar.

Penza Georgiasaurus (georgiasaurus pensensis) Georgiasaurs grew up to 4-5 meters in length. Judging by the size and proportions of the limbs, they were quite strong swimmers and lived in the open sea. These lizards ate mainly small fish and cephalopods, although they may not have disdained carrion that floated on the surface of the sea. Their teeth are versatile: they can both pierce and tear prey.

The sea was shallow, no more than a few tens of meters deep. Numerous archipelagos and shallows rose from the water, teeming with fry and shrimp. There was noise on the islands coniferous forests, dinosaurs roamed, and the water element was conquered by swimming lizards.

In the Jurassic period, the marine predators that occupied the top of the food pyramid were ichthyosaurs and plesiosaurs. Their bones are found in shales on the banks of the Volga. Flat slabs of slate, like a giant stone book, are often covered with impressions and shells as thickly as this page is covered with letters. The bones of lizards were especially often found in the first third of the last century, when an energy famine came to the country and the Volga region switched to local fuel - oil shale. Like mushrooms after rain, grandiose underground labyrinths of mines have appeared in Chuvashia, Samara, Saratov and Ulyanovsk regions.

Unfortunately, the miners were not interested in fossils. Usually the skeletons were destroyed during blasting, and the debris, along with the waste rock, went to the dump. Scientists have repeatedly asked miners to preserve the bones, but this has helped little. Director of the Paleontological Institute of the USSR Academy of Sciences, Academician Yuri Orlov, recalled how during an expedition he visited the workers at the mine and told them for a long time about the enormous value of ancient bones.

“Finds like yours serve as decoration for museums,” he said confidentially. To which the chief engineer replied: “Only stupid people go to museums...”

Clidastes. These lizards hunted cephalopods, fish and turtles. With their own length of up to five meters, they were not interested in large prey. Apparently, they mastered the technique of underwater flight, cutting through the water like penguins and sea turtles, and were excellent swimmers.

Some finds were still preserved, thanks to dedicated local historians. One of these enthusiasts was Konstantin Zhuravlev. In 1931, near his hometown of Pugachev in the Saratov region, oil shale began to be developed - first by opencast mining, then by mines.

Soon, broken bones, broken fish prints and shells appeared in the dumps. Zhuravlev began to frequently visit the mine, climbed onto the dumps and talked with the workers, explaining to them how important the fossils were. The miners promised to take a closer look at the rock and, if they come across something interesting, to notify the museum. Sometimes, in fact, they notified - but rarely and late. The local historian collected almost the entire collection himself.

Mostly he came across the remains of ichthyosaurs. Over the course of several years, Zhuravlev found many scattered teeth and vertebrae of two ichthyosaurs - Paraophthalmosaurus savelievsky(Paraophthalmosaurus saveljeviensis) and ochevia, later named after the discoverer (Otschevia zhuravlevi).

These were medium-sized lizards. They grew to three to four meters in length and, judging by the proportions of their bodies, were good swimmers, but probably preferred to hunt from ambush. At the moment of the throw, they may have developed a speed of up to 30-40 kilometers per hour - quite sufficient to keep up with small fish or cephalopods, their main prey.

One day a real giant escaped from Zhuravlev. At the end of the summer of 1932, he learned that miners, while digging a tunnel, for several days came across huge vertebrae of a lizard - they were called “carriages”. The miners did not attach any importance to this and threw everything away. Only one “stroller” survived, which was given to a local historian. Zhuravlev calculated that the destroyed skeleton reached 10-12 meters in length. Subsequently, the vertebra disappeared, and it is impossible to verify the calculations. However, there are also skeletons of 14-meter fish lizards in the world.

To match these giants were Jurassic plesiosaurs. Their remains are much less common than the bones of ichthyosaurs, and usually in the form of fragments. One day Zhuravlev picked up a half-meter-long fragment of the lower jaw from a dump, from which fragments of 20-centimeter teeth were sticking out.

Moreover, the surviving teeth were located in the back of the jaw, and one can only guess what kind of palisade adorned the mouth of this plesiosaur (the front teeth are much larger). The skull itself was apparently three meters high. A person would fit in it like in a bed. Most likely, the jaw belonged Liopleurodon russian(Liopleurodon rossicus) - one of the largest marine predators in the entire history of the Earth.

Lioprevrodon

“They grew up to 10-12 meters long, weighed 50 tons, but, judging by some bones, there were larger individuals, including in the Volga region,” says Maxim Arkhangelsky, associate professor at the Saratov University state university. - Unfortunately, there are no complete skeletons or skulls in the collections. It's not just that they are rare. Sometimes they were simply destroyed during oil shale mining.”

Soon after the end of the Great Patriotic War, an expedition of the Paleontological Institute discovered fragments of the skulls of two Liopleurodons in the mine dumps in Buinsk (Chuvash Republic) and Ozinki (Saratov Region). Each fragment is the size of a child.

Probably, the large skeleton found in the early 1990s at a mine near Syzran also belonged to Liopleurodon. Cracking open the shale, the combine's bucket hit a huge block. The teeth scraped its surface with a grinding sound, and sparks rained down. The worker climbed out of the cabin and examined the obstacle - a large nodule from which black bones, as if charred, were sticking out. The miner called the engineer. The work was suspended and local historians were called in. They photographed the skeleton, but did not remove it, deciding that it would take a lot of time. The mine management supported them: the face stood idle for a day already. The find was lined with explosives and blown up...

New times

Liopleurodons lived at the very end of the Jurassic period, when the Central Russian Sea reached largest sizes. “Several million years later, in the Cretaceous period, the sea broke up into separate, often desalinated bays and either left or returned briefly. A stable basin remained only in the south, reaching the borders of the present Middle and Lower Volga regions, where a grandiose archipelago stretched: many islands with lagoons and sandbanks,” explains paleontologist, professor at Saratov University Evgeniy Pervushov.

By that time, sea lizards had undergone great changes. The ichthyosaurs that swarmed the Jurassic seas almost became extinct. Their last representatives belonged to two genera - platypterygium(Platypterygius) and sveltonectes. A year ago, the first Russian sveltonectes(Sveltonectes insolitus), found in the Ulyanovsk region, is a two-meter fish-eating lizard.

Platypterygium was larger. One of the largest fragments was found 30 years ago in the vicinity of the Saratov village of Nizhnyaya Bannovka. It was with difficulty that the narrow and long front part of the skull was pulled out from the high Volga cliff. Judging by its size, the lizard reached six meters in length. The bones turned out to be unusual. “Extensive depressions are visible on the frontal part of the skull, and a number of holes are visible on the lower jaw. Dolphins have similar structures, and they are associated with echolocation organs. Probably, the Volga lizard could also navigate in the water by sending high-frequency signals and catching their reflection,” says Maxim Arkhangelsky.

But neither these nor other improvements helped the ichthyosaurs regain their former power. In the middle of the Cretaceous period, 100 million years ago, they finally left the arena of life, giving way to their long-time competitors - plesiosaurs.

Long neck

Ichthyosaurs lived only in water of normal salinity; desalinated bays or lagoons oversaturated with salt were not suitable for them. But the plesiosaurs didn’t care - they spread across a variety of sea basins. In the Cretaceous period, lizards with long neck. Last year, one of these giraffe lizards was described from Lower Cretaceous deposits - Abyssosaurus Natalia(Abyssosaurus nataliae). Its scattered remains were dug up in Chuvashia. This plesiosaur received its name - Abyssosaurus (“lizard from the abyss”) due to the structural features of its bones, which suggest that the seven-meter giant led a deep-sea lifestyle.

In the second half of the Cretaceous period, among plesiosaurs, giant elasmosaurs(Elasmosauridae) with an unusually long neck. They apparently preferred to live in shallow coastal waters, warmed by the sun and teeming with small animals. Biomechanical models show that elasmosaurs moved slowly and, most likely, like airships, hung motionless in the water column, bending their necks and collecting carrion, or fishing for passing fish and belemnites (extinct cephalopods).

We have not yet found complete skeletons of elasmosaurs, but individual bones form large clusters: in some places in the Lower Volga region from one square meter you can collect a “harvest” of several teeth and half a dozen vertebrae the size of a fist.

Short-necked animals lived together with elasmosaurs. plesiosaurs polycotylides(Polycotylidae). The skull of such a lizard was found in a small Penza quarry, where gray-yellow sandstone was mined and crushed. In the summer of 1972, a large slab with a strange convex pattern on the surface came across here. The workers were delighted: there was clay and puddles all around, and they could throw the stove at the change house and clean the dirt from the soles of their boots. One day, a worker, wiping his feet, noticed that strange lines formed a whole picture - the head of a lizard.

After some thought, he called the local museum. Local historians arrived at the quarry, cleared the slab and were amazed to see an almost complete imprint of the skull, spinal column and front flippers of the plesiosaur. To the question: “Where is the rest?” - The workers silently nodded towards the crusher. "Rug" moved to the museum. The bones were fragile and crumbled, but the imprints remained. Based on them, a new, so far the only species of Russian polycotylides was described - the Penza Georgiasaurus pensensis.

Last year, paleontologists, thanks to a discovery by scientists at the Natural History Museum in Los Angeles, finally discovered that plesiosaurs were viviparous reptiles.

But it was not plesiosaurs that became the main marine predators of the end of the dinosaur era. The true masters of the seas were mosasaurs, whose lizard ancestors descended into the sea in the middle of the Cretaceous period. Perhaps their homeland was precisely the Volga region: in Saratov, in an abandoned quarry on the slope of Bald Mountain, a fragment of the skull of one of the earliest mosasaurs was found. At the beginning of the 20th century, a complete skeleton of this lizard was apparently dug up in the Saratov province. But it was not scientists who found it, but peasants.

They broke out the blocks with bones and decided to sell them to a glue factory. Such factories were smoking all over the country. There they used the remains of cows, horses and goats to make glue, soap and bone meal for fertilizer. They also did not disdain fossil remains: a Ryazan bone factory once bought four skeletons of big-horned deer for processing. But only Saratov men thought of using a petrified lizard for soap...

By the end of the Cretaceous period, mosasaurs settled throughout the planet: their bones can now be found everywhere - in the American deserts, in the fields of New Zealand, in the quarries of Scandinavia. One of the richest deposits was discovered in the Volgograd region, not far from the Polunin farmstead, right on the collective farm melon patch.

Among the cracked lumps of hot earth, near the watermelons, lie dozens of rounded teeth and vertebrae of mosasaurs. Among them, the huge teeth of the Hoffmann mosasaurs, similar to browned bananas, stand out especially - the same one, next to which almost all other Cretaceous lizards looked like dwarfs.

Khans and kings of the Mesozoic era

The Hoffmann mosasaurus could be considered the largest Russian lizard, if not for the strange finds that are occasionally found in the Volga region. Thus, in the Ulyanovsk region, a fragment of the humerus of a Jurassic plesiosaur was once dug up - several times larger than usual. Then, in the Jurassic deposits of the Orenburg region, on the slope of Mount Khan’s Tomb, a piece of a hefty “thigh” of a plesiosaur was found. The length of these two lizards apparently approached 20 meters.

That is, they could be compared in size to whales and were the largest predators in the entire history of the Earth. Another time, near an abandoned shale mine, a vertebra the size of a bucket was found. Foreign experts considered it to be the bone of a huge dinosaur - titanosaur. However, one of the famous Russian experts on extinct reptiles, Saratov professor Vitaly Ochev, suggested that the vertebra could belong to a giant crocodile, up to 20 meters long.

Unfortunately, scattered fragments are not always suitable for scientific description. It is only clear that the subsoil of the Volga region holds many mysteries and will present more than one surprise to paleontologists. The skeletons of the planet's largest sea lizards may also be found here.

National Geographic No. 4 2012.

Marine reptiles

When studying life in the Mesozoic, perhaps the most striking thing is that almost half of all known species of reptiles lived not on land, but in water, in rivers, estuaries and even in the sea. We have already noted that in the Mesozoic, shallow seas became widespread on the continents, so there was no shortage of living space for aquatic animals.

In the Mesozoic layers there are a large number of fossil reptiles adapted for life in water. This fact can only mean that some reptiles returned back to the sea, to their homeland, where the ancestors of dinosaurs - fish - appeared long ago. This fact requires some explanation, since at first glance there was a regression here. But we cannot consider the return of reptiles to the sea to be a step backward from an evolutionary point of view simply on the grounds that Devonian fish came out of the sea onto land and developed into reptiles after passing through the amphibian stage. On the contrary, this position illustrates the principle according to which each actively developing group of organisms strives to occupy all varieties of the environment in which it can exist. In fact, the movement of reptiles into the sea is not very different from the colonization of rivers and lakes by amphibians in the Late Carboniferous (photo 38). There was food in the water and the competition was not too fierce, so first amphibians and then reptiles moved into the water. Already before the end of the Paleozoic, some reptiles became aquatic inhabitants and began to adapt to a new way of life. This adaptation went mainly along the path of improving the method of movement in the aquatic environment. Of course, reptiles continued to breathe air in the same way that a modern whale, a mammal, although similar in body shape to a fish, breathes air. Moreover, Mesozoic marine reptiles did not evolve from any one land reptile that decided to move back into the water. Fossil skeletons provide undeniable evidence that they had different ancestors and appeared at different times. Thus, fossil remains show how diverse the response of organisms was to changing environmental conditions, as a result of which a vast space was created, abundant in food and suitable for settlement.

Extensive information has been obtained from the study of fossil remains contained in marine mudstones and chalk limestones; These fine clastic rocks preserve not only bones, but also imprints of skin and scales. With the exception of the smallest and most primitive species, most marine reptiles were predators and belonged to three main groups: thyosaurs, plesiosaurs and mosasaurs. Briefly characterizing them, we must first note that ichthyosaurs acquired an elongated shape similar to fish (Fig. 50) and were excellently adapted to fast swimming in pursuit of fish or cephalopods. These animals, reaching 9 meters in length, had bare skin, a dorsal fin and a tail like a fish, and their four limbs turned into a kind of seal flippers and were used to control the movement of the body when swimming. All the fingers in these flippers were closely connected, and there were additional bones in them to increase strength. The large eyes of ichthyosaurs were adapted to see well in water. They even had one very significant improvement in the reproduction process. Being air-breathing animals that lived in seawater, they could not lay eggs. Therefore, ichthyosaurs developed a method of reproduction in which the embryo developed inside the mother’s body and, upon reaching maturity, was born alive. They became viviparous. This fact is established by the discovery of perfectly preserved remains of female ichthyosaurs with fully formed young inside their bodies, the number of young reaches seven.

Rice. 50. Four groups of animals that acquired a streamlined body shape as a result of adaptation to life in water: A. reptile, B. fish, C. bird, D. mammal. Initially they had different appearances, but in the course of evolution they acquired external similarities

The second group includes plesiosaurs, which, unlike the fish-like ichthyosaurs, retained the original body shape of reptiles, reaching 7.5-12 meters in length. If not for the tail, the plesiosaur would have looked like a giant swan. Of course, the ancestor of the plesiosaur was not at all the same land reptile that gave rise to the ichthyosaurs. The legs of plesiosaurs turned into long fins, and the head, set on a long neck, was equipped with sharp teeth that closed and reliably held the most slippery fish. Such teeth prevented chewing; The plesiosaur swallowed its prey whole and then crushed it in its stomach using pebbles. The diet of plesiosaurs can be judged from the stomach contents of one of them, which apparently died before the stones in its stomach had time to properly crush the food it swallowed. It was found that the bones and fragments of shells contained in the stomach belonged to fish, flying reptiles and cephalopods, which were swallowed whole, along with the shell.

The third group of marine reptiles was called mosasaurs because they were first discovered near the Moselle River, in northeastern France. They could be called “belated” because they appeared only in the Late Cretaceous, when ichthyosaurs had been populating the seas for almost 150 million years. The ancestors of mosasaurs were lizards rather than dinosaurs. Their length reached 9 meters, they had scaly skin, and their jaws were designed in such a way that they could open their mouths wide, like snakes.

A streamlined body as an adaptation to living conditions in an aquatic environment is found not only in ichthyosaurs and mosasaurs. The same can be seen in a number of animals that lived before and after the Mesozoic, and in the Mesozoic (Fig. 50).

It seemed that these toothy and big-eyed marine predators went extinct tens of millions of years ago, but there are reports that ichthyosaurs are still found in the seas and oceans. Although these ancient creatures are similar to dolphins in many ways, it is difficult to confuse them with them, because the distinctive feature of ichthyosaurs is their huge eyes.

Dolphin-like lizards-eyed

Of the marine predatory dinosaurs, we are most familiar with plesiosaurs, and this is not surprising, because the famous Nessie is classified precisely as this type of aquatic lizard. However, in the depths of the sea at one time there were other types of predatory reptiles, for example, ichthyosaurs, which inhabited the seas and oceans 175-70 million years ago. Ichthyosaurs, which look like dolphins, according to scientists, were once among the first dinosaurs to return to the water element.

Unlike the plesiosaur with its long neck, the head of the ichthyosaur, like that of fish, was integral with the body; it is not for nothing that the name of this reptile is translated as “fish lizard.” For the most part, ichthyosaurs were not large in size, their length was 3-5 meters. However, among them there were also giants, for example, in the Jurassic period, some species reached a length of 16 meters, and in the polar regions of Canada, paleontologists discovered the remains of an ichthyosaur about 23 meters long (!), which lived in the Late Triassic.

These were toothy creatures, and their teeth were replaced several times during their lives. It is especially worth stopping at the eyes of ichthyosaurs. These reptiles had very large eyes, reaching 20 cm in diameter in some species. According to scientists, this eye size suggests that ichthyosaurs hunted at night. The eyes were protected by a bone ring.

The skin of these lizards had neither scales nor horny plates; according to scientists, it was covered with mucus, which provided better gliding in the water. Although ichthyosaurs are very similar to dolphins, they had a fish-type spine that curved in a horizontal plane, so their tail, like ordinary fish, was located in a vertical plane.

What did ichthyosaurs eat? It was widely believed that they had a preference for extinct cephalopods belemnites, but a team of researchers led by Ben Kier from the South Australian Museum refuted this idea. Scientists have carefully examined the stomach contents of a fossilized ichthyosaur that lived 110 million years ago. It turned out that there were fish, small turtles and even a small bird in it. This study allowed us to refute the hypothesis that ichthyosaurs became extinct due to the disappearance of belemnites.

It is curious that these marine reptiles were viviparous; this feature is clearly proven by paleontological finds. Scientists have more than once found the fossilized remains of ichthyosaurs, in the belly of which there were skeletons of unborn cubs. Newborn ichthyosaurs were forced to immediately begin an independent life. According to scientists, as soon as they were born, they already knew how to swim perfectly and get their own food.

Mysterious “weevil whales”

Ichthyosaurs reached their greatest diversity in the Jurassic period, and became extinct at the end of the Cretaceous. Or maybe they didn’t become extinct? After all, there is the opinion of a number of scientists that the same ichthyosaurs were warm-blooded and could well adapt to changing conditions in the ocean. When these lizards that have survived to this day die or die, their remains sink to the bottom, scientists accordingly do not find them and consider ichthyosaurs extinct.

In the early 1980s, the sailor of the Soviet cargo ship A. B. Fedorov, while sailing in the Indian Ocean, observed unusual marine animals, according to his description, very similar to ichthyosaurs. An eyewitness recalled: “I saw a light brown back and a characteristic whale fountain, but... it was not a whale or a dolphin. I saw such an animal for the first and so far only time in my life. The fact that this is some kind of mutant is excluded. There were at least five of these long-faced, toothy “whales” with large saucer-like eyes. More precisely, the eyes were in the center of the saucers.”

If this observation was the only one, it could be assumed that the sailor was mistaken and mistook quite ordinary inhabitants of the ocean for unusual creatures. However, in the spring of 1978, two members of the crew of the fishing vessel V.F. Varivoda and V.I. Titov observed a very strange sea animal with a toothy mouth. Titov described it this way: “The steep, rounded back of the head rose above the water by about 1.5 meters; a white stripe stood out brightly on the upper jaw, which, gradually expanding, stretched from the end of the muzzle to the corner of the mouth and was bordered below by a narrow black stripe... In the profile of the head was cone-shaped. The height of the upper jaw at the level of the corner of the mouth was about one meter... The total length of the head was from one and a half to two meters.”

V.I. Titov told the senior researcher at the Cetacean Laboratory, Candidate of Biological Sciences A. Kuzmin, about the mysterious animal he had encountered. The scientist had known Titov for 10 years by that time, so he took his story seriously. It is curious that Titov told him that he had seen similar “weevil whales” in the Indian Ocean more than once, and such animals usually kept in a small flock of 6-7 individuals, sometimes including calves among them.

Kuzmin showed his acquaintance many photographs and drawings of various sea animals, but Titov never identified his “weevil.” But when an image of an ichthyosaur accidentally caught his eye, he said that it was very similar to the creatures he had met.

A very living fossil?

So, there are observations of trustworthy people who have seen unknown large marine animals that are very similar to ichthyosaurs that went extinct tens of millions of years ago. Why not assume that ichthyosaurs, which at one time were distributed almost everywhere in all seas and oceans, managed to survive to our time only by significantly reducing their habitat?

It should be noted that even Soviet scientists took the messages of Fedorov and Titov quite seriously; information about a meeting with a large marine animal unknown to science was published in 1979 in the journal “Knowledge is Power.” On the skepticism of scientists in lately, of course, was greatly influenced by the discovery of lobe-finned fish, which was considered long extinct. If she managed to survive to this day, then why couldn’t the ichthyosaur do it?

French scientists concluded that ichthyosaurs were warm-blooded. This conclusion was made on the basis of data on the content of the stable oxygen isotope 18 0 in the fossil remains of ichthyosaurs. It was possible to prove that the body temperature of marine reptiles was higher than the body temperature of fish that lived with them at the same time. This discovery by scientists suggests that ichthyosaurs could well have survived, especially since they did not feed on belemnites alone. It remains to be seen that more compelling evidence for the existence of these prehistoric animals will emerge. Fortunately, many sailors now have both cameras and video cameras, and we can well hope to see footage of a whole flock of big-eyed and toothy creatures from the Jurassic period frolicking in the waves.

Prepared by Andrey SIDORENKO

In previous publications we have already touched on the topic of dinosaurs. Then we were talking about the ten largest species known to science. Today we want to introduce you to a list of the ten most ferocious sea dinosaurs. So.

Shastasaurus is a genus of dinosaurs that lived at the end of the Triassic period (more than 200 million years ago) in the territory of modern North America and, possibly, China. His remains were discovered in California, British Columbia and the Chinese province of Guizhou. This predator is the largest marine reptile ever found on the planet. It could grow up to 21 meters in length and weigh 20 tons.

In ninth place in the ranking is Dakosaurus, a saltwater crocodile that lived in the late Jurassic - early Cretaceous period (more than 100.5 million years ago). It was a rather large, carnivorous animal, adapted almost exclusively to hunting large prey. It could grow up to 6 meters in length.

Thalassomedon is a genus of dinosaur that lived in North America about 95 million years ago. Most likely, he was the main predator of his time. Thalassomedon grew up to 12.3 m in length. The size of its flippers reached about 1.5–2 meters. The length of the skull was 47 centimeters, the length of the teeth was 5 cm. It ate fish.

Nothosaurus (Nothosaurus) is a sea lizard that lived 240–210 million years ago in the territory modern Russia, Israel, China and North Africa. It reached about 4 meters in length. It had webbed limbs, with five long fingers, which could be used both for movement on land and for swimming. Probably ate fish. The complete skeleton of Nothosaurus can be seen at the Natural History Museum in Berlin.

In sixth place on the list of the most ferocious marine dinosaurs is Tylosaurus, a large marine predatory lizard that inhabited the oceans at the end of the Cretaceous period (about 88–78 million years ago). It was the dominant marine predator of its time. Grew up to 14 m in length. It ate fish, large predatory sharks, small mosasaurs, plesiosaurs and waterfowl.

Thalattoarchon was a large marine reptile that lived more than 245 million years ago in what is now the western United States. The remains, consisting of part of the skull, spine, pelvic bones, and parts of the hind fins, were discovered in Nevada in 2010. Thalattoarchon is estimated to have been the apex predator of its time. It grew to be at least 8.6 m in length.

Tanystropheus is a genus of lizard-like reptiles that lived in the Middle Triassic about 230 million years ago. It grew up to 6 meters in length, and was distinguished by a very elongated and mobile neck, which reached 3.5 m. It led a predatory aquatic or semi-aquatic lifestyle, probably hunting near the shore for fish and cephalopods.

Liopleurodon is a genus of large carnivorous marine reptiles that lived at the turn of the Middle and Late Jurassic period (approximately 165 million to 155 million years ago). It is assumed that the largest known Liopleurodon was just over 10 m in length, but typical sizes for it range from 5 to 7 m (according to other sources 16-20 meters). Body weight is estimated at 1–1.7 tons. These apex predators likely hunted from ambush, attacking large cephalopods, ichthyosaurs, plesiosaurs, sharks, and other large animals they could catch.

Mosasaurus (Mosasaurus) is a genus of extinct reptiles that lived in the territory of modern Western Europe and North America during the Late Cretaceous - 70–65 million years ago. Their remains were first found in 1764 near the Meuse River. The total length of representatives of this genus ranged from 10 to 17.5 m. In appearance they resembled a mixture of fish (or whale) with a crocodile. They were in the water all the time, diving to a considerable depth. They ate fish, cephalopods, turtles and ammonites. According to some scientists, these predators are distant relatives of modern monitor lizards and iguanas.

Megalodon (Carcharocles megalodon) - extinct species prehistoric shark, which lived throughout the oceans 28.1–3 million years ago. It is the largest known predatory fish in history. Megalodon is estimated to have reached 18 meters in length and weighed 60 tons. In body shape and behavior it was similar to modern white shark. He hunted cetaceans and other large sea animals. It is interesting that some cryptozoologists claim that this animal could have survived to the present day, but apart from the huge teeth found (up to 15 cm in length), there is no other evidence that the shark still lives somewhere in the ocean.