The land of the Volga region keeps the remains of giants who plied the sea during the time of the dinosaurs.

In the early August morning of 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 the new time Mikhail Vedenyapin. He went down to the Prolom ravine, to a small machine-gun shooting range. There were no exercises that day, and in the ravine one could meet only boys who ran to collect cartridge cases.

Mikhail Vedenyapin had been living in Penza for two years, in exile. Before that, he was exiled by the tsarist courts, Admiral Kolchak promised to shoot him, and now the Bolsheviks did not like his views. And now the former professional revolutionary SR works as a statistician, at his leisure he writes notes in the journal Hard Labor and Exile and wanders around the neighborhood in search of fossils. He, like many scientists and just curious of those times, has ten years left to live ...

He walked along the slope of a deep ravine, picking up from the ground the shells of mollusks that lived in a long time ago - more than 80 million years ago - the disappeared sea. In one place, the sandy slope was broken by machine-gun fire, 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 from. It didn't take long to search: huge bones stuck 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 Socialist-Revolutionary gathered friends and began excavations. However, the bones lay at a depth of seven meters - the excavation had to be expanded. This required diggers, and for them - a salary. Vedenyapin turned to the authorities for help. The Gubernia Executive Committee went to meet him and gave him a hundred rubles. From funds intended for the improvement of the city.

The modern museum of dinosaurs in the village of Undory (Ulyanovsk region). Many plesiosaur bones have been found in local slate mines.

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

In the confusion, a couple of bones were stolen, and Vedenyapin asked the police to send a squad for protection. It did not 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 the notes about the insidious priests and where the butter and sugar had disappeared, there was a call: “A convincing request to those present not to interfere with the work and comply with the requirements of the excavators!”.

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

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

In the first days of September, two preparators of the Russian Geological Committee arrived in Penza and, according to the newspaper, immediately "began work on exposing the mosasaurus and excavating it." The bones had to be removed before the slope sank due to the rains. And the shooting range has been idle for half a month. For a couple of days, the find was cleared of the rock. 19 large, laterally flattened teeth 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. The regional museum was then presented with a plaster copy. As it turned out, the remains belonged to the giant, who lived at the end of the dinosaur era - Hoffmann's Mosasaurus (Mosasaurus hoffmanni), one of the last marine lizards. Mosasaurs were real colossi.

But they were not the only ones who lived in the Central Russian Sea, which existed on the territory Central Russia during the Mesozoic era. During the Jurassic and Cretaceous periods of this era, many dynasties of lizards have changed. 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 all in the Volga region, a giant cemetery of sea giants.

The sea came to the eastern outskirts of Europe about 170 million years ago, in the middle of the Jurassic period. “The general rise in the level of the World Ocean in the Mesozoic era gradually led to the fact that the eastern part of Europe was under water. Then it was still not a sea, but rather a bay, stretching like a long tentacle from the south into the depths of the mainland. Later, the waves of the Boreal Sea moved from the north to the continent.

On the territory of the current Volga region, the bays met and formed a sea, which geologists called the Central Russian Sea, ”says a senior researcher at the Geological Institute Russian Academy Sciences Mikhail Rogov. 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.

Georgiasaurus Penza (georgiasaurus pensensis) Georgiasaurs grew up to 4-5 meters in length. Judging by the size and proportions of their limbs, they were quite strong swimmers and lived in the open sea. These lizards fed mainly on small fish and cephalopods, although they probably did not disdain 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 shoals rose from the water, teeming with fry and shrimps. Coniferous forests roared on the islands, dinosaurs roamed, and swimming lizards conquered the water element.

In the Jurassic, 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 slate slabs, resembling a giant stone book, are often covered with imprints and shells as densely as this page is with letters. The bones of lizards were found especially often in the first third of the last century, when energy hunger came to the country and in the Volga region they switched to local fuel - oil shale. Like mushrooms after rain, grandiose underground labyrinths of mines 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 the miners to save the bones, but this did little to help. Academician Yury Orlov, director of the Paleontological Institute of the USSR Academy of Sciences, recalled how during the expedition he went to the workers at the mine and told them for a long time about the great value of ancient bones.

“Such finds as yours serve as an adornment of museums,” he said confidentially. To which the chief engineer replied: “Only rotozees go to museums ...”

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

Some finds still managed to be preserved - thanks to local historians devoted to their work. One of these enthusiasts was Konstantin Zhuravlev. In 1931, near his hometown of Pugachev in the Saratov region, they began to develop shale - first in an open way, then in mines.

Soon, broken bones, broken fish prints and shells appeared in the dumps. Zhuravlev began to visit the mine often, climbed onto the dumps and talked with the workers, explaining to them how important fossils are. The miners promised to look closely at the breed and, if something interesting comes across, notify the museum. Sometimes, in fact, they were informed - but rarely and belatedly. The ethnographer collected almost the entire collection himself.

Basically, he came across the remains of ichthyosaurs. For 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).

They were medium sized lizards. They grew up to three or four meters long and, judging by the proportion of the body, were good swimmers, but they probably preferred to hunt from ambush. At the time of the throw, they may have developed speeds of up to 30-40 kilometers per hour - quite sufficient to keep up with small fish or cephalopods, their main prey.

Once a real giant slipped away from Zhuravlev. At the end of the summer of 1932, he learned that the miners, laying a tunnel, for several days stumbled upon the huge vertebrae of the lizard - they were called "carriages". The miners did not attach any importance to this and threw everything away. Only one "carriage" has survived, which was given to the 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, in the world there are skeletons and 14-meter fish-lizards.

To match these giants were jurassic plesiosaurs. Their remains are much rarer than ichthyosaur bones, and usually in the form of fragments. Once, Zhuravlev picked up a half-meter fragment of the lower jaw from the dump, from which fragments of 20-centimeter teeth protruded.

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, apparently, was three meters high. A person would fit in it, as in a bed. Most likely, the jaw belonged Liopleurodon Russian(Liopleurodon rossicus) - one of the largest marine predators in the history of the Earth.

Lioprevrodon

“They grew up to 10-12 meters long, weighed 50 tons, but, judging by some bones, there were individuals even larger, including in the Volga region,” says Maxim Arkhangelsky, associate professor of the Saratov 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 the extraction of shale.

Shortly after the end of the Great Patriotic War An expedition of the Paleontological Institute found fragments of the skulls of two liopleurodons in the dumps of mines in Buinsk (Chuvash Republic) and Ozinki (Saratov Region). Each piece is the size of a child.

Probably, a large skeleton found in the early 1990s in a mine near Syzran also belonged to Liopleurodon. Cracking open the shale, the combine's bucket hit a huge boulder. The teeth gnashed against its surface, sparks raining down. The worker got out of the cab and examined the obstacle - a large concretion, from which black, as if charred, bones protruded. The miner called the engineer. The work was suspended, local historians were called. They photographed the skeleton, but did not take it out, deciding that it would take a long time. The management of the mine supported them: the face was idle for a day. The find was surrounded by 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 for a short time. A stable basin was preserved only in the south, reaching the borders of the current Middle and Lower Volga region, where a grandiose archipelago stretched: many islands with lagoons and sandbars, ”explains paleontologist, professor at Saratov University Evgeny Pervushov.

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

The platipterygium was larger. One of the largest fragments was found 30 years ago in the vicinity of the Saratov village of Nizhnyaya Bannovka. From the high Volga cliff, with difficulty, they managed to pull out the narrow and long front part of the skull. Judging by its size, the lizard reached six meters in length. The bones were unusual. “There are extensive depressions on the frontal part of the skull, and a series of holes on the lower jaw. Dolphins have similar structures and are associated with echolocation organs. Probably, the Volga pangolin could also navigate in the water, sending high-frequency signals and capturing 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 longtime competitors - the 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 did not care - they spread across a variety of sea basins. In the Cretaceous period, lizards with a long neck began to predominate among them. Last year, one of these giraffe lizards was described from the Lower Cretaceous deposits - abyssosaurus natalia(Abyssosaurus nataliae). Its scattered remains were dug up in Chuvashia. This plesiosaur got its name - Abyssosaurus ("lizard from the abyss") due to the structural features of the bones, which suggest that the seven-meter giant led a deep-sea lifestyle.

In the second half of the Cretaceous, among the plesiosaurs, there were 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 living creatures. 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 fish and belemnites (extinct cephalopods) passing by.

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

Short necks lived 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: all around - clay, puddles, and the stove can be thrown at the change house and clean off the dirt from the soles of the boots. Once a worker, while wiping his feet, noticed that the strange lines add up to a whole picture - the head of a lizard.

On reflection, he called the local museum. Local historians came to the quarry, cleared the slab and were amazed to see an almost complete imprint of the skull, vertebral 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 brittle and crumbled, but the imprints remained. According to them, a new, so far the only species of Russian polycotylids, the Penza Georgiasaurus (Georgiasaurus pensensis), was described.

Last year, paleontologists, thanks to the discovery of scientists from the Museum natural history in Los Angeles, finally found out that plesiosaurs were viviparous reptiles.

But plesiosaurs did not become the main marine predators of the end of the dinosaur era. True hosts seas were mosasaurs whose lizard ancestors descended into the sea in the mid-Cretaceous. It is possible that the Volga region was their homeland: 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, apparently, a complete skeleton of this lizard was dug up in the Saratov province. But it was not scientists who found it, but peasants.

They broke out blocks of bones and decided to sell them to the smelter. Such factories smoked all over the country. There, the remains of cows, horses and goats were used to make glue, soap and bone meal for fertilizer. Fossil remains were also not disdainful: the Ryazan ivory plant once bought four skeletons of large-horned deer for processing. But only the Saratov peasants thought of using the petrified lizard for soap ...

By the end of the Cretaceous period, mosasaurs settled all over 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 locations was opened in the Volgograd region, not far from the Polunina farm, right on the collective farm melon.

Among the cracked clods hot earth, dozens of rounded teeth and vertebrae of mosasaurs lie near the watermelons. Among them, the huge, brown banana-like teeth of Hoffmann's mosasaurs stand out - the very one next to which almost all other Cretaceous lizards looked like dwarfs.

Khans and kings of the Mesozoic era

Mosasaurus Hoffmann could be considered the largest Russian lizard, if not for the strange finds that are occasionally found in the Volga region. So, 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 with whales in size and were the largest predators in the entire history of the Earth. Another time, near an abandoned slate mine, a vertebra the size of a bucket was caught. 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, under 20 meters long.

Unfortunately, scattered fragments are not always suitable for scientific description. It is only clear that the bowels of the Volga region hold many mysteries and will present more than one surprise to paleontologists. There may also be skeletons of the largest marine lizards on the planet.

National Geographic No. 4 2012.

This time was distinguished by a warm, even climate, low oxygen content in the atmosphere and hydrosphere. High temperatures and lack of oxygen have allowed reptiles to fill many ecological niches. The geography of the settlement of marine reptiles was huge, including they massively mastered the sea. In addition, the absence of polar caps led to an increase in the level of the World Ocean: it rose 300 meters higher than it is now. Many territories that we used to consider dry land were hidden under water: most of Europe, almost all of European Russia, large parts of the USA, Asia and Africa. The shallow epicontinental seas have become an excellent environment for the life of sea lizards.

One of the most notable groups were the plesiosaurs. They thrived in the Jurassic and Cretaceous periods, giving rise to many amazing forms, and not just toothy predators. There were, for example, long-necked filter feeders that fed on fry or krill. However, by the end of the Cretaceous period, the group began to lose its former diversity. Only long-necked elasmosaurs remained in the seas (see the Long-necked problem, as well as their unusual relatives, Polycotylidae).

Polycotylids are medium-sized reptiles. They, like large dolphins, usually grew up to 3-4 meters in length. Polycotylides have spread widely throughout the planet, their remains have been found on all continents, including Antarctica. They were adapted to fishing and outwardly resembled piscivorous pliosaurs, such as the Ulyanovsk luskhan: they had the same narrow jaws with rows of small teeth. Only the neck of the polycotylids was slightly longer. In Russia, several of their more or less complete skeletons were found, as well as numerous individual bones in different regions of the Volga region (see picture of the day Mosasaurus of the Volga region).

In the Penza region, near the village of Zatolokino, a sandstone quarry used to work. The boulders here were crushed into rubble and the surrounding roads were poured. In the summer of 1972, workers came across a large block with a strange pattern on the surface. They threw the stove at the change house and began to clean the soles of their boots on it. One worker noticed that strange lines add up to a whole picture - some kind of bones. On reflection, he called the local museum. Local historians confirmed that the remains of a marine reptile were found. Altogether, the workers preserved five blocks of sandstone, later found to contain the skull and front part of the plesiosaur skeleton. The back of the skeleton was lost: these blocks of sandstone had already been crushed into rubble. The length of the entire skeleton, according to the workers, was about seven meters. The surviving slabs were taken to the Penza Museum of Local Lore. The museum expressed its gratitude to the Bekovsky District Committee of the CPSU for assistance in preserving and transporting the “historical find”.

The preservation of the bones was unusual. All the bones crumbled away, leaving only impressions and cavities inside the sandstone, including a unique detail: a cast of the brain cavity. The reptile was buried on its back. A piece of the palate protruded from the sandstone (the lower jaw was not preserved). At the same time, the flippers lay down as if the reptile lifted them up. The discovery was briefly described by professor of Saratov State University, paleontologist VG Ochev. The diagnosis was built on the bones protruding from the sandstone. Ochev identified the reptile as a new genus and named it in honor of his late father: Penza Georgiosaurus ( Georgiasaurus penzensis).

A few years ago, they decided to study the find more thoroughly and get pictures of all the bones using tomography. We managed to negotiate with a local tomographer in Penza, who agreed to do all the work for free. Four small blocks were shot quickly. And the fifth, the largest and most important - with a skull - simply did not fit in the tomograph. It was necessary to cut off 5 centimeters of rock along the edges of the slab. The skull would not have suffered - it lies in the middle of the slab. However, the local history museum did not dare to cut the exhibit, and there were no larger tomographs in Penza. As a result, the skull is still not really studied. Only the palate and part of the braincase are described. The rest lies inside the sandstone and waits in the wings.

Now this find, in fact, can only be accurately determined up to the polycotylidae family and may turn out to be one of several genera. Her ancestry belongs to a separate genus Georgiasaurus so far in doubt. Without skull tomography precise definition impossible.

Two other incomplete skeletons of polycotylids were found in the Saratov and Orenburg regions. Unfortunately, the preservation of bone material from the Saratov region made it possible to identify the reptile only to the family. The femur of the found polycotylides, however, has some similarities with the remains of the American

The ocean is the cradle of life and the place of endless experiments of nature. It was in it that she tested, for example, an important innovation characteristic of modern highly developed organisms - live birth. The ancient ichthyosaur lizards, unlike their plesiosaur relatives, completely moved to the ocean, became similar to fish in body shape and learned to bear cubs in themselves, which is very important in the conditions of ocean depths and latitudes. Although the palm of primacy in live birth still belongs to the ancient armored fish, the stage of return to it in dinosaurs was undoubtedly very important for evolution.

However, the evolutionary features of ancient oceanic reptiles are not limited to this. The new data showed that

marine dinosaurs, unlike land relatives, were warm-blooded, that is, they could maintain a stable body temperature above temperature environment.

The work of French and Danish scientists is published Science.

French paleobiologists have developed a technology to "measure" the body temperature of ancient lizards. Conclusions about the body temperature of ichthyosaurs, plesiosaurs, and mosasaurs were made on the basis of data on the isotopic composition (in terms of oxygen in phosphates) of reptile teeth that have survived to this day. The study showed that they maintained a constant body temperature by traveling across the ocean from tropical to cold latitudes, where water temperatures vary considerably.

“This method opens up great opportunities for us. Now we can use it to comprehensively study the evolution of marine reptiles,” said Professor Ryosuke Motania, a paleontologist at the University of California. He became the author response articles, published in the same issue of Science as the French study.

In his article, he called the discovery the development of a "thermometer in the teeth of fish."

"Thermometer" works by comparing the isotopic composition of the substances of the teeth of ancient lizards and cold-blooded fish, which have an ambient temperature. In the Earth's atmosphere, oxygen is represented by several isotopes, in particular the most common oxygen-16 and the less common oxygen-18. In the process of growth, animals "absorb" both isotopes; then they are "deposited" in their bones and teeth. The ratio of isotopes, in turn, is determined by the temperature of the organisms.

Initially, scientists assumed that ancient reptiles were as cold-blooded as modern ones. If this is so, then the “temperature signal” of oxygen isotopes in the teeth of these animals can only speak of the temperature of the environment surrounding them millions of years ago. The temperature of a priori cold-blooded fish was taken as a starting point: it was precisely influenced only by the ambient temperature.

So scientists "measured" the temperature of ancient water in which ichthyosaurs, plesiosaurs and mosasaurs swam. These three branches of the dinosaur tree were significantly different from each other. Ichthyosaurs were the most integrated into the aquatic environment, they were "dolphin-like" reptiles and could well dive to noticeable depths. Plesiosaurs were more like modern sea lions and fur seals with a long neck and four flippers. They swam less than ichthyosaurs. Mosasaurs, on the other hand, lived along the coasts and were sedentary, hunting their victims from ambushes. All three animal groups flourished between 250 and 65 million years ago.

However, studies have shown that the assumption of "room" body temperature was incorrect. Ichthyosaurs and plesiosaurs successfully maintained a high body temperature - up to 39 degrees. Mosasaurs controlled heat to a lesser extent and were more dependent on the environment for this. This is in good agreement with the way of life of reptiles: a stable body temperature is more necessary for mobile hunters than sitting in ambush.

However, the figure of 39 degrees may seem too high, notes Motani in his article. Even in modern dolphins - highly developed mammals - the body temperature is approximately equal to that of a human. Only birds are much "warmer", from 38 to 43 degrees, but they live in a completely different environment.

He suggested that an unaccounted error associated with a change in the isotopic composition of the Earth's atmosphere crept into the method.

Correction of temperatures for the changed isotopic composition gave reasonable data: the body temperature of ichthyosaurs was about 24 degrees.

This is in good agreement with the data on the body temperature of modern fish capable of thermoregulation - tuna and swordfish. They maintain a temperature 6-10 degrees above the ambient water temperature.

Modern animals have developed different mechanisms for keeping warm. If tuna maintain the temperature due to a high (compared to other fish) metabolic rate, then leatherback turtles, for example, are saved big size and a layer of fat. Ichthyosaurs and plesiosaurs may have used similar mechanisms, Motani said. He suggests that an improved method of measuring body temperature will help explore the evolution of marine reptiles from pangolins to dolphin-like creatures. Most likely, warm-bloodedness was not their original property, but came along with a change in body shape to more “fish”. This hypothesis remains to be tested by scientists.

Elasmosaurs are ancient lizards of the plesiosaur order. They reigned on the planet in the Triassic period, and in the Cretaceous period they were gone.

The average body length of Elasmosaurus was about 15 meters. The spine was formed from a large number of flat vertebrae, which 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 previously 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 the teeth were shaped like spikes.

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

These lizards could catch the fastest fish, the long neck helped to grab agile prey.

At times, these dinosaurs went to shallow water, lay down on the bottom and swallowed small pebbles, which helped to 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.

For the first time, the remains of this creature were found in 1868 by E. Kop. Elasmosaur bones have been found in the United States, Japan, and Russia. These dinosaurs got their name from the flat bones of the pelvic and shoulder girdle.

marine reptiles

When studying life in the Mesozoic, perhaps the most striking thing is that almost half of all known reptile species 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 were 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 to life in the water. This fact can only mean that some reptiles returned back to the sea, to their homeland, where once upon a time the ancestors of dinosaurs appeared - fish. 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 an evolutionary backward step merely on the grounds that the Devonian fish emerged from the sea onto land and developed into reptiles through the amphibian stage. On the contrary, this proposition illustrates the principle that each actively developing group of organisms tends to occupy all the varieties of environment in which it can exist. In fact, the movement of reptiles into the sea is not too 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 way of movement in the aquatic environment. Of course, the reptiles continued to breathe air in the same way as the modern whale breathes air, a mammal, although similar in body shape to a fish. Moreover, the Mesozoic marine reptiles did not evolve from any one land reptile that made the decision to go back into the water. Fossil skeletons provide undeniable evidence that they had different ancestors and appeared at different times. Thus, fossil remains show how varied the response of organisms to changing environmental conditions was, as a result of which a vast expanse abounding in food and suitable for settlement was created.

Extensive information has been obtained from the study of fossils contained in marine mudstones and Cretaceous limestones; in these fine clastic rocks, not only bones are preserved, 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 chief groups: Ich-thiosaurs, 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 for fast swimming in pursuit of fish or cephalopods. These animals, reaching 9 meters in length, had bare skin, a dorsal fin and 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 fingers in these flippers were closely connected, and additional bones existed in them to increase strength. Big eyes ichthyosaurs were adapted to see well in the water. They even had one very significant improvement in the process of reproduction. 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, reaching maturity, was born alive. They became viviparous. This fact is established by the finds of excellently preserved remains of female ichthyosaurs with fully formed cubs inside their bodies, the number of cubs 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 a different appearance, but in the course of evolution they acquired an external resemblance.

The second group includes plesiosaurs, which, unlike fish-like ichthyosaurs, retained the original shape of the reptile body, 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 terrestrial reptile that gave rise to the ichthyosaurs. The legs of the plesiosaurs turned into long fins, and the head, planted on a long neck, was equipped with sharp teeth that closed and securely held the most slippery fish. Such teeth excluded chewing; The plesiosaurus swallowed its prey whole and then crushed it in the stomach with the help of pebbles. The diet of plesiosaurs can be judged from the stomach contents of one of them, which apparently died before the stones in his stomach had time to crush the food he swallowed to the right extent. The bones and fragments of shells contained in the stomach were found to belong to fish, flying reptiles and cephalopods, which were swallowed whole, along with the shell.

A third group of marine reptiles are called mosasaurs because they were first discovered near the Moselle River in northeastern France. They could be called "late" because they appeared in the late Cretaceous time, when ichthyosaurs had inhabited 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 arranged in such a way that they could open their mouths wide, like snakes.

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