Marine representatives have three orders of reptiles - turtles, lizards and snakes. Some sea snakes are not associated with land at all, even during breeding, since they are viviparous, never leave the sea and would be completely helpless on land. Sea turtles spend most of their lives in the open ocean, but return to the sandy tropical coasts to breed; Only females come to land to lay eggs, and males never set foot on land after hatching and moving to the sea.
Sea lizards are more associated with land. An example is the Galapagos marine iguana Amblyrhynchus crisiatus. She lives in the surf on the Galapagos Islands, climbs rocks and eats only algae. The fourth order of modern reptiles, crocodiles, apparently has no truly marine representatives. Living in salt water, Crocodylus porosus is associated mainly with estuaries; it feeds primarily on fish and probably cannot survive for long in a true marine environment.
^The kidneys of reptiles are not adapted to excrete excess salt, and it is excreted by salt-secreting (or simply salt) glands located in the head. Salt glands produce a highly concentrated fluid that contains mainly sodium and chlorine in concentrations much higher than in seawater. These glands do not function continuously like a kidney; they secrete their secretions only occasionally in response to a salt load that increases plasma salt concentrations. Similar glands are present in seabirds, in which they have been studied in detail.
In the wet lizard, the salt glands pour out their secretion into the anterior part of the nasal cavity, which has a ridge that prevents the liquid from flowing back and being swallowed. Sometimes, with a sharp exhalation, liquid is ejected from the nostrils in the form of small splashes. The Galapagos iguana feeds only on algae, which are similar in salt content to seawater. Therefore, the animal needs a mechanism to excrete salts in high concentrations (Schmidt-Nielsen, Fanne 1958). s'
Sea turtles, both herbivorous and carnivorous, have large salt-secreting glands located in the orbits of both eyes. The gland duct opens in the posterior corner of the orbit, and the turtle, which has received a salt load, cries truly salty tears. (Human tears, which, as everyone knows, have a salty taste, are isosmotic with blood plasma. Therefore, the lacrimal glands in humans do not play a special role in the elimination of salt.)
^Sea snakes also secrete salty fluid when exposed to salt and have salt glands that open into the oral cavity, from where the secreted fluid is excreted (Dunson, 1968). Sea snakes are close relatives of cobras and are very poisonous, which has somewhat slowed down the physiological study of their salt metabolism, which has a number of interesting aspects.
Although marine reptiles have a mechanism for excreting salt in the form of a very concentrated liquid, the question remains whether many of them actually drink water in significant quantities?

The Paleozoic era was 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 appears to be consistent with the data we have on the movements of crustal plates. 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 of 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 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 in the Mesozoic, vast seas were widespread.

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 were neither ferocious nor large in size.

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 the appearance and lifestyle of dinosaurs. Therefore, we can move on to describing some of the most outstanding representatives of the 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 man who leans on two legs. 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 Triassic fossil species that had unusual armor, protrusions and spines suggests that they were already beginning to “take” protective measures against their enemies - other 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 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 "armored" ankylosaur-like dinosaur (2) and the 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 ate 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 deliver a strong kick to its prey, 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 a shell helmet. The trees are palm trees, 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, quadrupedal, amphibian-like dinosaurs had even smaller brains relative to their body weight than other dinosaurs, although the group was not particularly renowned 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 it was possessed by many different species of 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 changing 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 those of 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 two-legged 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 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 is 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 rough seas 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 the 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. One of the genera developed a special protrusion, or crest, at 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 Jurassic times, reptiles living along the shores of warm seas had various 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, with large 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 of the 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 by the sun's 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 the air, switching 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. Of the invertebrates, most cephalopods disappeared, including all belemnites, as well as some lines 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 of 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 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.

Thanks to the discoveries of recent years, the study of sea lizards of the Mesozoic, which for a long time remained in the shadow of their distant terrestrial relatives - dinosaurs, is experiencing a real renaissance. Now we can quite confidently reconstruct the appearance and habits of giant aquatic reptiles - ichthyosaurs, pliosaurs, mosasaurs and plesiosaurs.

The skeletons of aquatic reptiles became known to science among the first, playing an important role in the development of the theory of biological evolution. The massive jaws of a mosasaurus, found in 1764 in a quarry near the Dutch city of Maastricht, clearly confirmed the fact of the extinction of animals, which was a radically new idea at that time. And at the beginning of the 19th century, discoveries of skeletons of ichthyosaurs and plesiosaurs made by Mary Anning in southwestern England provided rich material for research in the field of the still emerging science of extinct animals - paleontology.

Nowadays, marine reptile species - saltwater crocodiles, sea snakes and turtles, and Galapagos iguana lizards - make up only a small proportion of the reptiles living on the planet. But in the Mesozoic era (251-65 million years ago) their number was incomparably greater. This, apparently, was favored by the warm climate, which allowed animals incapable of maintaining a constant body temperature to feel great in water, an environment with a high heat capacity. In those days, sea lizards roamed the seas from pole to pole, occupying the ecological niches of modern whales, dolphins, seals and sharks. For more than 190 million years, they formed a “caste” of top predators, hunting not only fish and cephalopods, but also each other.

Back in the water

Like aquatic mammals - whales, dolphins and pinnipeds, sea lizards descended from air-breathing land-based ancestors: 300 million years ago, it was reptiles that conquered land, managing, thanks to the appearance of eggs protected by a leathery shell (unlike frogs and fish), to move from reproduction to water to reproduce outside the aquatic environment. Nevertheless, for one reason or another, one or another group of reptiles at different periods again “tried their luck” in the water. It is not yet possible to accurately indicate these reasons, but, as a rule, the development of a new niche by a species is explained by its unoccupied position, the availability of food resources and the absence of predators.

The real invasion of lizards into the ocean began after the largest Permian-Triassic extinction event in the history of our planet (250 million years ago). Experts are still arguing about the causes of this disaster. Various versions have been put forward: the fall of a large meteorite, intense volcanic activity, a massive release of methane hydrate and carbon dioxide. One thing is clear: over a period of time that is extremely short by geological standards, out of all the diversity of species of living organisms, only one in twenty managed to avoid becoming a victim of an environmental disaster. The deserted warm seas provided great opportunities for the “colonizers,” and this is probably why several groups of marine reptiles arose in the Mesozoic era. Four of them were truly unparalleled in number, diversity and distribution. Each group - ichthyosaurs, plesiosaurs, their relatives the pliosaurs, and mosasaurs - consisted of predators that occupied the top of the food pyramids. And each of the groups gave birth to colossi of truly monstrous proportions.

The most important factor that determined the successful development of the aquatic environment by Mesozoic reptiles was the transition to viviparity. Instead of laying eggs, females gave birth to fully formed and fairly large young, thereby increasing their chances of survival. Thus, the life cycle of the reptiles discussed here now took place entirely in the water, and the last thread connecting the sea lizards with the land was broken. Subsequently, apparently, it was this evolutionary acquisition that allowed them to leave shallow waters and conquer the open sea. Not having to go ashore removed size restrictions, and some marine reptiles took advantage of gigantism. Growing up isn't easy, but once you've grown up, try to beat him. He will offend anyone himself.

Ichthyosaurs - bigger, deeper, faster

The ancestors of fish-lizard ichthyosaurs, who mastered the aquatic environment about 245 million years ago, were medium-sized inhabitants of shallow waters. Their body was not barrel-shaped, like those of their descendants, but elongated, and its bending played an important role in movement. However, over the course of 40 million years, the appearance of ichthyosaurs changed significantly. The initially elongated body became more compact and ideally streamlined, and the caudal fin with a large lower blade and a small upper one in most species was transformed into almost symmetrical.

Paleontologists can only guess about the family relationships of ichthyosaurs. It is believed that this group separated very early from the evolutionary trunk, which later gave rise to such branches of reptiles as lizards and snakes, as well as crocodiles, dinosaurs and birds. One of the main problems still remains the lack of a transitional link between the terrestrial ancestors of ichthyosaurs and primitive marine forms. The first fish lizards known to science are already completely aquatic organisms. It is difficult to say what their ancestor was.

The length of most ichthyosaurs did not exceed 2–4 meters. However, among them there were also giants, reaching 21 meters. Such giants included, for example, Shonisaurs, who lived at the end of the Triassic period, about 210 million years ago. These are some of the largest marine animals that have ever lived in the oceans of our planet. In addition to their enormous size, these ichthyosaurs were distinguished by a very long skull with narrow jaws. To imagine a shonisaurus, as one American paleontologist joked, you need to inflate a huge rubber dolphin and greatly stretch its face and fins. The most interesting thing is that only the young had teeth, while the gums of the adult reptiles were toothless. You may ask: how did such colossi eat? To this we can answer: if Shonisaurs were smaller, then one could assume that they chased prey and swallowed it whole, as do swordfish and its relatives - marlin and sailfish. However, twenty-meter giants could not be fast. Perhaps they fed themselves with small schooling fish or squid. There is also an assumption that adult shonisaurs used a filtration apparatus like a whalebone, which allowed them to strain plankton from the water. By the beginning of the Jurassic period (200 million years ago), species of ichthyosaurs appeared in the seas, relying on speed. They deftly pursued fish and swift belemnites - extinct relatives of squids and cuttlefish. According to modern calculations, the three- to four-meter ichthyosaur stenopterygius developed a cruising speed no less than one of the fastest fish, tuna (dolphins swim twice as slow) - almost 80 km/h or 20 m/s! In water! The main propellant of such record holders was a powerful tail with vertical blades, like those of fish.

In the Jurassic period, which became the golden age of ichthyosaurs, these lizards were the most numerous marine reptiles. Some species of ichthyosaurs could dive to depths of up to half a kilometer or more in search of prey. These reptiles could distinguish moving objects at such a depth due to the size of their eyes. So, the diameter of the eye of Temnodontosaurus was 26 centimeters! Only the giant squid has more (up to 30 centimeters). The eyes of ichthyosaurs were protected from deformation during rapid movement or at great depth by a unique eye skeleton - supporting rings consisting of more than a dozen bone plates developing in the eye shell - the sclera.

The elongated muzzle, narrow jaws and shape of the teeth of fish lizards indicate that they ate, as already mentioned, relatively small animals: fish and cephalopods. Some species of ichthyosaurs had sharp, conical teeth that were good for grabbing nimble, slippery prey. In contrast, other ichthyosaurs had broad teeth with blunt or rounded tips to crush the shells of cephalopods such as ammonites and nautilids. However, not so long ago, the skeleton of a pregnant female ichthyosaur was discovered, inside which, in addition to fish bones, they found the bones of young sea turtles and, most surprisingly, the bone of an ancient seabird. There is also a report of the discovery of remains of a pterosaur (flying lizard) in the belly of a fish lizard. This means that the diet of ichthyosaurs was much more diverse than previously thought. Moreover, one of the species of early fish lizards discovered this year, which lived in the Triassic (about 240 million years ago), had serrated edges of the rhombic cross-section of its teeth, which indicates its ability to tear off pieces from prey. Such a monster, which reached a length of 15 meters, had practically no dangerous enemies. However, for unclear reasons, this branch of evolution stopped in the second half of the Cretaceous period, about 90 million years ago.

In the shallow seas of the Triassic period (240–210 million years ago), another group of reptiles flourished - the nothosaurs. In their lifestyle, they most closely resembled modern seals, spending part of their time on the shore. Nothosaurs were characterized by an elongated neck, and they swam with the help of a tail and webbed feet. Gradually, some of them replaced their paws with fins, which were used as oars, and the more powerful they were, the more the role of the tail weakened.

Nothosaurs are considered the ancestors of plesiosaurs, which the reader knows well from the legend of the monster from Loch Ness. The first plesiosaurs appeared in the mid-Triassic (240–230 million years ago), but their heyday began at the beginning of the Jurassic period, that is, about 200 million years ago.

At the same time, pliosaurs appeared. These marine reptiles were closely related, but they looked different. Representatives of both groups - a unique case among aquatic animals - moved with the help of two pairs of large paddle-shaped fins, and their movements were probably not unidirectional, but multidirectional: when the front fins moved down, the rear fins moved up. It can also be assumed that only the front fin blades were used more often - this saved more energy. The hind ones were put to work only during attacks on prey or rescue from larger predators.

Plesiosaurs are easily recognized by their very long necks. For example, in Elasmosaurus it consisted of 72 vertebrae! Scientists even know skeletons whose necks are longer than the body and tail combined. And, apparently, it was the neck that was their advantage. Although plesiosaurs were not the fastest swimmers, they were the most maneuverable. By the way, with their disappearance, long-necked animals no longer appeared in the sea. And one more interesting fact: the skeletons of some plesiosaurs were found not in marine, but in estuarine (where rivers flowed into the seas) and even freshwater sedimentary rocks. Thus, it is clear that this group did not live exclusively in the seas. For a long time, it was believed that plesiosaurs fed mainly on fish and cephalopods (belemnites and ammonites). The lizard slowly and imperceptibly swam up to the flock from below and, thanks to its extremely long neck, snatched the prey, clearly visible against the background of the light sky, before the flock rushed to its heels. But today it is obvious that the diet of these reptiles was richer. The found skeletons of plesiosaurs often contain smooth stones, probably specially swallowed by the lizard. Experts suggest that it was not ballast, as previously thought, but real millstones. The muscular section of the animal’s stomach, contracting, moved these stones, and they crushed the strong shells of mollusks and crustacean shells that had fallen into the womb of the plesiosaur. Skeletons of plesiosaurs with remains of bottom invertebrates indicate that in addition to species that specialized in hunting in the water column, there were also those that preferred to swim near the surface and collect prey from the bottom. It is also possible that some plesiosaurs could switch from one type of food to another depending on its availability, because a long neck is an excellent “fishing rod” with which it was possible to “catch” a wide variety of prey. It is worth adding that the neck of these predators was a rather rigid structure, and they could not sharply bend or lift it out of the water. This, by the way, casts doubt on many stories about the Loch Ness monster, when eyewitnesses report that they saw exactly a long neck sticking out of the water. The largest of the plesiosaurs is the New Zealand Mauisaurus, which reached 20 meters in length, almost half of which was a giant neck.

The first pliosaurs, which lived in the late Triassic and early Jurassic periods (about 205 million years ago), closely resembled their plesiosaur relatives, initially misleading paleontologists. Their heads were relatively small, and their necks were quite long. Nevertheless, by the middle of the Jurassic period, the differences became very significant: the main trend in their evolution was an increase in the size of the head and the power of the jaws. The neck, accordingly, became short. And if plesiosaurs hunted mainly for fish and cephalopods, then adult pliosaurs chased other marine reptiles, including plesiosaurs. By the way, they didn’t disdain carrion either.

The largest of the first pliosaurs was the seven-meter Romaleosaurus, but its size, including the size of its meter-long jaws, pales in comparison with the monsters that appeared later. The oceans of the second half of the Jurassic period (160 million years ago) were ruled by Liopleurodons - monsters that may have reached 12 meters in length. Later, in the Cretaceous period (100–90 million years ago), colossi of similar sizes lived - Kronosaurus and Brachauchenius. However, the largest pliosaurs were the Late Jurassic period.

Liopleurodons, which inhabited the depths of the sea 160 million years ago, could move quickly with the help of large flippers, which they flapped like wings.

Even more?!

Recently, paleontologists have been incredibly lucky with sensational finds. Thus, two years ago, a Norwegian expedition led by Dr. Jorn Hurum extracted fragments of the skeleton of a giant pliosaur from the permafrost on the island of Spitsbergen. Its length was calculated from one of the skull bones. It turned out - 15 meters! And last year, in the Jurassic sediments of Dorset County in England, scientists had another success. On one of the beaches of Weymouth Bay, local fossil collector Kevin Sheehan dug up an almost completely preserved huge skull measuring 2 meters 40 centimeters! The length of this “sea dragon” could be as much as 16 meters! Almost the same length was the juvenile pliosaur found in 2002 in Mexico and named the Monster of Aramberri.

But that's not all. The Natural History Museum at Oxford University houses a gigantic lower jaw of a macromerus pliosaur measuring 2 meters 87 centimeters! The bone is damaged, and it is believed that its total length was no less than three meters. Thus, its owner could reach 18 meters. Truly imperial sizes.

But pliosaurs were not just huge, they were real monsters. If anyone posed a threat to them, it was themselves. Yes, the huge, whale-like Shonisaurus ichthyosaur and the long-necked Mauisaurus plesiosaur were longer. But the colossal pliosaur predators were ideal “killing machines” and had no equal. Three-meter fins quickly carried the monster towards the target. Powerful jaws with a palisade of huge teeth the size of bananas crushed bones and tore the flesh of victims, regardless of their size. They were truly invincible, and if anyone can be compared with them in power, it was the fossil megalodon shark. Tyrannosaurus rex next to giant pliosaurs looks like a pony in front of a Dutch draft horse. Taking a modern crocodile for comparison, paleontologists calculated the pressure that the jaws of the huge pliosaur developed at the moment of the bite: it turned out to be about 15 tons. Scientists got an idea of ​​the power and appetite of the eleven-meter Kronosaurus, who lived 100 million years ago, by “looking” into its belly. There they found the bones of a plesiosaur.

Throughout the Jurassic and much of the Cretaceous period, plesiosaurs and pliosaurs were the dominant ocean predators, although it should not be forgotten that there were always sharks nearby. One way or another, large pliosaurs went extinct about 90 million years ago for unclear reasons. However, as you know, a holy place is never empty. They were replaced in the seas of the late Cretaceous by giants that could compete with the most powerful of the pliosaurs. We are talking about mosasaurs.

Mosasaurus to mosasaurus - lunch

The group of mosasaurs, which replaced and perhaps supplanted the pliosaurs and plesiosaurs, arose from an evolutionary branch close to monitor lizards and snakes. In mosasaurs that completely switched to life in water and became viviparous, their paws were replaced by fins, but the main mover was a long, flattened tail, and in some species it ended in a fin like a shark’s. It can be noted that, judging by the pathological changes found in the fossilized bones, some mosasaurs were able to dive deeply and, like all extreme divers, suffered from the consequences of such dives. Some species of mosasaurs fed on benthic organisms, crushing mollusk shells with short, wide teeth with rounded tops. However, the conical and slightly bent back terrible teeth of most species leave no doubt about the eating habits of their owners. They hunted fish, including sharks, and cephalopods, crushed turtle shells, swallowed seabirds and even flying lizards, and tore apart other marine reptiles and each other. Thus, half-digested plesiosaur bones were found inside a nine-meter-long tylosaur.

The design of the skull of mosasaurs allowed them to swallow even very large prey whole: like snakes, their lower jaw was equipped with additional joints, and some bones of the skull were articulated movably. As a result, the open mouth was truly monstrous in size. Moreover, two additional rows of teeth grew on the roof of the mouth, making it possible to hold prey more firmly. However, we should not forget that mosasaurs were also hunted. The five-meter-long Tylosaurus found by paleontologists had a crushed skull. The only one who could do this was another, larger mosasaurus.

Over 20 million years, mosasaurs rapidly evolved, giving rise to giants comparable in mass and size to monsters from other groups of marine reptiles. Towards the end of the Cretaceous period, during the next great extinction, giant sea lizards disappeared along with dinosaurs and pterosaurs. Possible causes of a new environmental disaster could be the impact of a huge meteorite and (or) increased volcanic activity.

The first to disappear, even before the Cretaceous extinction, were the pliosaurs, and somewhat later the plesiosaurs and mosasaurs. It is believed that this happened due to a disruption in the food chain. The domino principle worked: the extinction of some massive groups of unicellular algae led to the disappearance of those who fed on them - crustaceans, and, as a consequence, fish and cephalopods. Marine reptiles were at the top of this pyramid. The extinction of mosasaurs, for example, could be a consequence of the extinction of ammonites, which formed the basis of their diet. However, there is no final clarity on this issue. For example, two other groups of predators, sharks and teleosts, which also fed on ammonites, survived the Late Cretaceous extinction event with relatively few losses.

Be that as it may, the era of sea monsters is over. And only after 10 million years sea giants will appear again, but not lizards, but mammals - the descendants of the wolf-like Pakicetus, which was the first to master the coastal shallow waters. Modern whales trace their ancestry from him. However, that's another story. Our magazine talked about this in the first issue of 2010.

An unimaginable event occurred about 251 million years ago, which significantly influenced subsequent eras. The name given by scientists to this event is the Permian-Tertiary extinction, or Great Extinction.

It became the formative boundary between two geological periods - the Permian and Triassic, or, in other words, between the Paleozoic and Mesozoic. It took a little time for most marine and terrestrial species to cease to exist.

These events contributed to the formation of a group of archosaurs on land (the most prominent representatives are dinosaurs) and the so-called. "sea dinosaurs"

Because It would be incorrect to call dinosaurs marine; we put such a phrase as “sea dinosaurs” in quotation marks and ask you to be lenient towards such an “amateurish” definition later in the article (editor’s note).

Marine reptiles inhabited the aquatic territories of the Mesozoic along with land dinosaurs. They also disappeared at the same time - about 65.5 million years ago. The cause was the Cretaceous-Paleogene extinction.

In this article we would like to introduce you to a selection of the 10 most striking and ferocious representatives of “sea dinosaurs”.

Shastasaurus is a genus of “dinosaurs” that existed more than 200 million years ago – the end of the Triassic period. According to scientists, their habitat was the territory of modern North America and China.

The remains of Shastasaurs have been found in California, British Columbia and the Chinese province of Guizhou.

Shastasaurus belongs to the ichthyosaurs - marine predators similar to modern dolphins. Being the largest reptile in water, individuals could grow to unimaginable sizes: body length - 21 meters, weight - 20 tons.

But, despite their large size, Shastasaurs were not exactly terrible predators. They ate by sucking and ate mainly fish.

Dakosaurus are saltwater crocodiles that lived more than 100.5 million years ago: Late Jurassic - Early Cretaceous.

The first remains were discovered in Germany, and later their habitat expanded from England to Russia and Argentina.

Dakosaurs were large, carnivorous animals. The maximum length of the body, reptilian and fish-like at the same time, did not exceed 6 meters.

Scientists who have studied the structure of the teeth of this species believe that the dracosaurus was the main predator during its period of residence.

Dracosaurs hunted exclusively for large prey.

Thalassomedon are “dinosaurs” belonging to the pliosaur group. Translated from Greek - “lord of the sea.” They lived 95 million years ago in the territory of the North. America.

The body length reached 12.5 meters. Huge flippers, which allowed him to swim at incredible speeds, could grow up to 2 meters. The size of the skull was 47 cm, and the teeth were approximately 5 cm. The main diet was fish.

The dominance of these predators remained until the late Cretaceous period, and ceased only with the advent of mosasaurs.

Nothosaurus are “sea lizards” that existed during the Triassic period - about 240-210 million years ago. They were found in Russia, Israel, China, and North Africa.

Scientists believe that nothosaurs are relatives of pliosaurs, another type of deep-sea predator.

Nothosaurs were extremely aggressive predators, and their body reached a length of up to 4 m. The limbs were webbed. There were 5 long fingers, intended for both movement on land and swimming.

The teeth of predators were sharp, directed outward. Most likely, nothosaurs ate fish and squid. It is believed that they attacked from ambush, using their sleek, reptilian physique to stealthily approach the food, thereby catching it by surprise.

A complete skeleton of Nothosaurus is in the Natural History Museum, Berlin.

Sixth place on our list of “sea dinosaurs” is Tylosaurus.

Tylosaurus is a species of mosasaurus. A large predatory “lizard” that lived in the oceans 88-78 million years ago - the end of the Cretaceous period.

Huge Tylosaurs reached 15 meters in length, thus being the apex predators of their time.

The diet of tylosaurs was varied: fish, large predatory sharks, small mosasaurs, plesiosaurs, and waterfowl.

Thalattoarchon is a marine reptile that existed during the Triassic period - 245 million years ago.

The first fossils discovered in Nevada in 2010 gave scientists new insights into the ecosystem's rapid recovery after the Great Dying.

The found skeleton - part of the skull, spine, pelvic bones, part of the hind fins - was the size of a school bus: about 9 m in length.

Thalattoarchon was an apex predator, growing up to 8.5 m.

Tanystropheus are lizard-like reptiles that existed 230 - 215 million years ago - the Middle Triassic period.

Tanystropheus grew up to 6 meters in length, had a 3.5-meter elongated and mobile neck.

They were not exclusively aquatic inhabitants: most likely, they could lead both an aquatic and semi-aquatic lifestyle, hunting near the shore. Tanystropheus were predators that ate fish and cephalopods.

Liopleurodon are large carnivorous marine reptiles. They lived about 165-155 million years ago - the boundary of the Middle and Late Jurassic period.

Typical dimensions of Liopleurodon are 5-7 meters in length, weight - 1-1.7 tons. It is believed that the most famous large representative was more than 10 meters in length.

Scientists believe that the jaws of these reptiles reached 3 m.

During its period, Liopleurodon was considered an apex predator, dominating the food chain.

They hunted from ambush. They fed on cephalopods, ichthyosaurs, plesiosaurs, sharks and other large animals.

Mosasaurus - reptiles of the late Cretaceous period - 70-65 million years ago. Habitat: the territory of modern Western Europe and North America.

The first remains were discovered in 1764 near the Meuse River.

The appearance of the mosasaurus is a mixture of a whale, fish and crocodile. There were hundreds of sharp teeth.

They preferred to eat fish, cephalopods, turtles and ammonites.

Research by scientists suggests that mosasaurs may be distant relatives of modern monitor lizards and iguanas.

The first place is rightfully occupied by the prehistoric shark, considered a truly terrible creature.

Carcharocles lived 28.1-3 million ago - the Cenozoic era.

This is one of the largest predators in the history of marine life. It is considered the ancestor of the great white shark - the most terrible and powerful predator today.

The body length reached up to 20 m, and the weight reached 60 tons.

Megalodons hunted cetaceans and other large aquatic animals.

An interesting fact is that some cryptozoologists believe that this predator could have survived to the present day. But, fortunately, apart from the huge 15-centimeter teeth found, there is no other evidence.

Elasmosaurs are ancient lizards of the plesiosaur order. They reigned on the planet in the Triassic period, and in the Cretaceous period they were no longer there.

The average body length of Elasmosaurus was about 15 meters. The spine was formed from a large number of flat vertebrae, of which there could be up to 150 pieces.

The evolutionary process changed the limbs of elasmosaurs and turned them into large flippers.

These dinosaurs once lived in the sea, which was once located on the site of modern Kansas.

Elasmosaurs were the most unusual creatures of the suborder. They had a very long and flexible neck ending in a small head. At the same time, the elasmosaurus had a wide mouth, and its teeth were shaped like spikes.

In terms of the number of cervical vertebrae, these dinosaurs are certainly in first place among the rest. For example, you can compare the cervical region of a giraffe, which consists of only 7 vertebrae.

These lizards could catch the fastest fish; their long neck helped them grab agile victims.

At times, these dinosaurs went to shallow water, lay down on the bottom and swallowed small pebbles, which helped crush food and acted as ballast. About 250 stones were found in the stomach of one lizard. After studying the stones, scientists realized that elasmosaurs traveled several thousand kilometers throughout their lives and collected stones in different parts of the coast. Most likely, the offspring of elasmosaurs, like other ichthyosaurs, were born in the sea.

The remains of this creature were first found in 1868 by E. Kop. Bones of elasmosaurs have been found in the United States, Japan and Russia. These dinosaurs got their name due to the flat bones of the pelvic and shoulder girdle.