Water lizards. Volga sea lizards. reptiles in the air
Thanks to the findings of recent years, the study of Mesozoic marine lizards, 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 were among the first to become known to science, having played 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 for that time was a radically new idea. And at the beginning of the 19th century, the finds of ichthyosaur and plesiosaur skeletons 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, as well as Galapagos iguana lizards - make up only a small fraction of the reptiles that live on the planet. But in the Mesozoic era (251-65 million years ago), their number was incomparably greater. This, apparently, was favored by a 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 plied the seas from pole to pole, occupying the ecological niches of modern whales, dolphins, seals and sharks. For more than 190 million years, they constituted a "caste" of top predators, preying not only on fish and cephalopods, but also on each other.
Back in the water
Like aquatic mammals - whales, dolphins and pinnipeds, sea lizards descended from air-breathing terrestrial ancestors: 300 million years ago, it was the reptiles that conquered the land, having managed, thanks to the emergence of eggs protected by a leathery shell (unlike frogs and fish), to switch from reproduction to water to reproduction outside the aquatic environment. Nevertheless, for one reason or another, then one or another group of reptiles at different periods again “tried their luck” in the water. It is not yet possible to specify these reasons precisely, but, as a rule, the development of a new niche by a species is explained by its unemployment, the presence of food resources, and the absence of predators.
The real invasion of the pangolins into the ocean began after the largest Permian-Triassic extinction in the history of our planet (250 million years ago). Experts still argue about the causes of this catastrophe. Various versions are put forward: the fall of a large meteorite, intense volcanic activity, a massive release of methane hydrate and carbon dioxide. One thing is clear - for an extremely short period of time by geological standards, out of the whole variety of species of living organisms, only one in twenty managed to avoid becoming a victim of an ecological catastrophe. The deserted warm seas provided the "colonizers" with great opportunities, and this is probably why several groups of marine reptiles arose in the Mesozoic era at once. Four of them were truly unparalleled in number, diversity and distribution. Each of the groups - ichthyosaurs, plesiosaurs, their relatives pliosaurs, as well as mosasaurs - consisted of predators that occupied the tops of the food pyramids. And each of the groups spawned colossi of truly monstrous proportions.
The most important factor that determined the successful development of the Mesozoic reptiles of the aquatic environment was the transition to live birth. Instead of laying eggs, females gave birth to fully formed and fairly large cubs, thereby increasing their chances of survival. Thus, the life cycle of the reptiles in question now took place entirely in the water, and the last thread connecting the sea lizards with the land was broken. In the future, apparently, it was this evolutionary acquisition that allowed them to leave shallow waters and conquer the open sea. The lack of need to go ashore lifted size restrictions, and some of the marine reptiles took advantage of gigantism. Growing up big is not easy, but if you have grown up, try to overcome this. He will offend anyone.
Ichthyosaurs - Bigger, Deeper, Faster
The ancestors of fish lizards, ichthyosaurs, who mastered the aquatic environment about 245 million years ago, were medium-sized inhabitants of shallow waters. Their body was not barrel-shaped, as in the 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 originally elongated body became more compact and perfectly streamlined, and the caudal fin with a large lower lobe and a small upper lobe in most species was transformed into an almost symmetrical one.
Paleontologists can only guess about the family ties of ichthyosaurs. It is believed that this group separated very early from the evolutionary trunk, which subsequently 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. What was their ancestor, while it is difficult to say.
The length of most ichthyosaurs did not exceed 2–4 meters. However, among them were giants, reaching 21 meters. Such hulks 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 huge size, these ichthyosaurs were distinguished by a very long skull with narrow jaws. To imagine Shonisaurus, as one American paleontologist joked, you have to inflate a huge rubber dolphin and stretch its muzzle and fins strongly. The most interesting thing is that only the young had teeth, while the gums of adult reptiles were toothless. You ask: how did such colossi eat? This can be answered: if shonisaurs were smaller, then one could assume that they chased prey and swallowed it whole, as swordfish and its relatives, marlin and sailfish, do. However, twenty-meter giants could not be fast. Perhaps they satiated 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), ichthyosaur species appeared in the seas, relying on speed. They deftly pursued fish and swift belemnites - extinct relatives of squid and cuttlefish. According to modern calculations, the three-four-meter ichthyosaur stenopterygius developed a cruising speed no less than one of the fastest fish, tuna (dolphins swim twice as slowly), almost 80 km / h or 20 m / s! In water! The main mover of such champions was a powerful tail with vertical blades, like a fish.
In the Jurassic period, which became the golden age of ichthyosaurs, these lizards were the most numerous marine reptiles. Some species of ichthyosaurs in search of prey could dive to a depth of half a kilometer or more. These reptiles could distinguish moving objects at such a depth due to the size of their eyes. So, in the darkdontosaurus, the diameter of the eye was 26 centimeters! More (up to 30 centimeters) - only in the giant squid. From deformations during rapid movement or at great depths, the eyes of ichthyosaurs were protected by a kind of eye skeleton - supporting rings, consisting of more than a dozen bone plates developing in the shell of the eye - 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 wide, blunt or rounded teeth 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 sea bird. There is also a report about the discovery of the remains of a pterosaur (flying pangolin) in the belly of a fish lizard. And 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 that lived in the Triassic (about 240 million years ago), the edges of the rhombic teeth in the cross section were serrated, which indicates its ability to tear pieces from prey. Such a monster, reaching a length of 15 meters, had practically no dangerous enemies. However, this branch of evolution, for unclear reasons, stopped in the second half of the Cretaceous period, about 90 million years ago.
In the shallow waters of the seas of the Triassic period (240-210 million years ago), another group of reptiles flourished - notosaurs. In their way of life, they most of all 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, in some of them, the paws were replaced by fins, which were used as oars, and the more powerful they were, the more the role of the tail weakened.
Nothosaurs are considered to be the ancestors of the plesiosaurs, which the reader is well aware of from the legend of the monster from Loch Ness. The first plesiosaurs appeared in the middle of the Triassic (240-230 million years ago), but their heyday began at the beginning of the Jurassic period, that is, about 200 million years ago.
Then the pliosaurs appeared. These marine reptiles were close relatives, but they looked different. Representatives of both groups - a case unique 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 ones moved up. It can also be assumed that only the front fin blades were used more often - this way more energy was saved. The rear ones were connected to work only during throws for prey or rescue from larger predators.
Plesiosaurs are easily recognizable by their very long necks. So, for example, in Elasmosaurus, it consisted of 72 vertebrae! Scientists even know of skeletons whose necks are longer than the body and tail combined. And, apparently, it was the neck that was their advantage. Let plesiosaurs were not the fastest swimmers, but 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 from behind and, thanks to its extra long neck, snatched out prey, clearly visible against the bright 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 stomach of the animal, contracting, moved these stones, and they crushed strong shells of mollusks and shells of crustaceans that fell into the womb of a plesiosaur. Skeletons of plesiosaurs with the remains of benthic invertebrates indicate that, in addition to species that specialized in hunting in the water column, there were also those that preferred, swimming near the surface, to 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 the long neck is a great "fishing rod" with which you could "catch" a 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, calls into question 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, who lived in the late Triassic and early Jurassic periods (about 205 million years ago), strongly resembled their plesiosaur relatives, initially misleading paleontologists. Their heads were relatively small, and their necks were rather long. Nevertheless, by the middle of the Jurassic, 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 also did not disdain carrion.
The largest of the first pliosaurs was the seven-meter rhomaleosaurus, but its size, including the size of its meter-long jaws, pales in comparison with the monsters that appeared later. In the oceans of the second half of the Jurassic period (160 million years ago), lyopleurodons were in charge - monsters that could reach 12 meters in length. Later, in the Cretaceous period (100-90 million years ago), colossi of similar sizes lived - kronosaurs and brachaucheniuses. However, the largest were the pliosaurs of the late Jurassic period.
Liopleurodons, who 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 unspeakably lucky with sensational finds. So, two years ago, a Norwegian expedition led by Dr. Jorn Khurum removed fragments of the skeleton of a giant pliosaurus from the permafrost on the island of Svalbard. Its length was calculated from one of the bones of the skull. It turned out - 15 meters! And last year, in the Jurassic deposits of Dorset County in England, scientists were waiting for 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 was the length of a young pliosaurus found in 2002 in Mexico and named the Monster of Aramberri.
But that's not all. The Oxford University Museum of Natural History houses a giant lower jaw of a macromerus pliosaurus, the size of which is 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 size.
But pliosaurs were not just huge, they were real monsters. If anyone posed a threat to them, it was they themselves. Yes, the huge, whale-like ichthyosaur schonisaurus and the long-necked plesiosaur mauisaur were longer. But the colossal predators of the pliosaurs were ideal "killing machines" and had no equal. Three-meter fins rapidly carried the monster to the target. Mighty jaws with a palisade of huge banana-sized teeth crushed the bones and tore the flesh of the victims, regardless of their size. They were truly invincible, and if anyone can be compared with them in power, it is the fossil megalodon shark. Tyrannosaurus rex next to giant pliosaurs looks like a pony in front of a Dutch heavy truck. Taking a modern crocodile for comparison, paleontologists calculated the pressure that the jaws of a huge pliosaurus developed at the time of the bite: it turned out to be about 15 tons. The idea of \u200b\u200bthe power and appetite of an eleven-meter kronosaurus that lived 100 million years ago was obtained by scientists by “looking” into its belly. There they found the bones of a plesiosaur.
Throughout the Jurassic and much of the Cretaceous, plesiosaurs and pliosaurs were the dominant ocean predators, although it should not be forgotten that sharks were always around. One way or another, large pliosaurs became 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're talking about mosasaurs.
Mosasaurus mosasaurus - lunch
The group of mosasaurs, which replaced, and perhaps replaced the pliosaurs and plesiosaurs, arose from an evolutionary branch close to monitor lizards and snakes. Mosasaurs who completely switched to life in water and became viviparous had their legs replaced by fins, but the main mover was a long flattened tail, and in some species it ended in a shark-like fin. It can be noted that, judging by the pathological changes found in the fossilized bones, some mosasaurs were able to dive deep and, like all extreme divers, suffered from the consequences of such diving. Some species of mosasaurs fed on benthic organisms, crushing mollusk shells with short, wide teeth with rounded tops. However, the conical and slightly recurved terrible teeth of most species leave no doubt about the food habits of their owners. They hunted fish, including sharks and cephalopods, crushed turtle shells, swallowed seabirds and even flying pangolins, tore apart other marine reptiles and each other. So, half-digested bones of a plesiosaur were found inside a nine-meter tylosaurus.
The design of the skull of mosasaurs allowed them to swallow whole even very large prey: like snakes, their lower jaw was equipped with additional joints, and some bones of the skull articulated movably. As a result, the open mouth was truly monstrous in size. Moreover, two additional rows of teeth grew in it on the palate, which made it possible to hold prey more firmly. However, do not forget that mosasaurs were also hunted. The skull of a five-meter Tylosaurus found by paleontologists was crushed. The only one who could do that was another, larger mosasaurus.
For 20 million years, mosasaurs evolved rapidly, giving giants comparable in mass and size to monsters from other groups of marine reptiles. By 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 ecological catastrophe could be the impact of a huge meteorite and (or) increased volcanic activity.
The first, and even before the Cretaceous extinction, were the pliosaurs, and somewhat later, the plesiosaurs and mosasaurs. It is believed that this happened due to a violation of food chains. The domino principle worked: the extinction of some mass groups of unicellular algae led to the disappearance of those who fed on them - crustaceans, and, as a result, fish and cephalopods. Marine reptiles were at the top of this pyramid. The extinction of mosasaurs, for example, could be due to 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 bony fish that also fed on ammonites, survived the Late Cretaceous extinction era with relatively few losses.
Whatever it was, but the era of sea monsters is over. And only after 10 million years, sea giants will reappear, but not lizards, but mammals - the descendants of the wolf-like pakicetus, the first to master the shallow coastal waters. Modern whales lead their pedigree from it. However, that's another story. Our magazine told about it in the first issue of 2010.
Dinosaurs were the dominant vertebrates that inhabited all the ecosystems of planet Earth for over 160 million years - from the Triassic period (about 230 million years ago) to the end of the Cretaceous period (about 65 million years ago). I want to acquaint you with a list of the ten most ferocious marine dinosaurs.
10 Shastasaurus
Shastasaurus (Shastasaurus) - a genus of dinosaurs that lived at the end of the Triassic period (more than 200 million years ago) in the territory of modern North America and, possibly, China. His remains have been found in California, British Columbia and the Chinese province of Guizhou. This predator is the largest marine reptile ever found on the planet. It could grow up to 21 meters in length and weigh 20 tons.
9 Dacosaurus
In ninth place in the ranking is Dakosaurus, a marine crocodile that lived in the late Jurassic - early Cretaceous period (more than 100.5 million years ago). It was a fairly large, carnivorous animal, adapted almost exclusively to hunting large prey. Can grow up to 6 meters in length.
8. Thalassomedon
Thalassomedon is a genus of dinosaurs that lived in North America about 95 million years ago. Most likely, it was the main predator of its time. Thalassomedon grew up to 12.3 m in length. The size of its flippers reached about 1.5–2 meters. The length of the skull was 47 centimeters, teeth - 5 cm. He ate fish.
7. Nothosaurus
Nothosaurus (Nothosaurus) is a marine lizard that lived 240-210 million years ago in the territory of modern Russia, Israel, China and North Africa. In length reached about 4 meters. It had webbed limbs, with five long fingers that could be used both for movement on land and for swimming. Probably ate fish. A complete Nothosaurus skeleton can be seen at the Natural History Museum in Berlin.
6. Tylosaurus
In sixth place in the list of the most ferocious marine dinosaurs is Tylosaurus (Tylosaurus) - a large marine predatory lizard that inhabited the oceans at the end of the Cretaceous period (about 88-78 million years ago). It was the dominant marine predator of its time. It grew up to 14 m in length. It fed on fish, large predatory sharks, small mosasaurs, plesiosaurs, and waterfowl.
5. Talattoarchon
Talattoarchon (Thalattoarchon) - a large marine reptile that lived more than 245 million years ago in what is now the western part of the United States. The remains, consisting of part of the skull, spine, pelvic bones, and part of the hind fins, were discovered in Nevada in 2010. According to estimates, talattoarchon was the top predator of his time. It grew to at least 8.6 m in length.
4. Tanystropheus
Tanystropheus is a genus of lizard-like reptiles that lived in the Middle Triassic about 230 million years ago. It grew up to 6 meters in length, and was distinguished by a very elongated and mobile neck, which reached 3.5 m. It led a predatory aquatic or semi-aquatic lifestyle, probably hunting fish and cephalopods near the coast.
3. Liopleurodon
Liopleurodon (Liopleurodon) - a genus of large carnivorous marine reptiles that lived at the turn of the middle and late Jurassic period (from about 165 million to 155 million years ago). It is assumed that the largest known Liopleurodon was just over 10 m in length, but typical sizes for it range from 5 to 7 m (according to other sources, 16-20 meters). Body weight is estimated at 1-1.7 tons. These apex predators probably ambushed large cephalopods, ichthyosaurs, plesiosaurs, sharks, and other large animals they could catch.
2 Mosasaurus
Mosasaurus (Mosasaurus) is a genus of extinct reptiles that lived on the territory of modern Western Europe and North America during the Late Cretaceous - 70-65 million years ago. For the first time their remains were found in 1764 near the river Meuse. The total length of representatives of this genus ranged from 10 to 17.5 m. In appearance, they resembled a mixture of a fish (or a whale) with a crocodile. All the time they were in the water, plunging to a considerable depth. They ate fish, cephalopods, turtles and ammonites. According to some scientists, these predators are distant relatives of modern monitor lizards and iguanas.
1. Megalodon
Megalodon (Carcharocles megalodon) is an extinct species of prehistoric shark that lived throughout the oceans 28.1–3 million years ago. It is the largest known predatory fish in history. Megalodon is estimated to have reached 18 meters in length and weighed 60 tons. In body shape and behavior, it was similar to the modern white shark. He hunted cetaceans and other large marine animals. Interestingly, some cryptozoologists claim that this animal could have survived to the present, but apart from the found huge teeth (up to 15 cm in length), there is no other evidence that the shark still lives somewhere in the ocean.
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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 as a step back from an evolutionary point of view only on the grounds that the Devonian fishes emerged from the sea onto land and developed into reptiles, passing 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 carnivores and belonged to three main groups: ichthyosaurs, plesiosaurs, and mosasaurs. Briefly characterizing them, we must first of all 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. The large eyes of 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).
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.
If you have been to the Galapagos Islands, then you have certainly met a marine iguana. The photo of this animal looks intimidating, but it is not without a special harsh beauty. Marine iguanas are reminiscent of dinosaurs that lived many millions of years ago. It is these animals that we want to pay special attention to in this article.
What does a marine iguana look like?
Lifestyle
Iguanas have sharp eyesight and are excellent swimmers and divers. On land, they have no enemies, so they allow themselves to be slow and lazy. But in the water you often have to escape from sharks, so slowness here can be fatal. Therefore, the marine iguana habits adjust, depending on the environment in which it is located.
The favorite pastime of lizards on land is to bask in the sun. This is due to the peculiarities of thermoregulation of the animal. The temperature of his body depends on the environment, and in order to get enough energy for the normal process of life, it is necessary to accumulate heat and distribute it throughout the body. Overheating of the marine iguana does not threaten. It releases excess heat through the skin of the belly.
Relationships in the family
Darwin called marine iguanas so terrible the appearance of these lizards seemed to him. But in fact, they are not too aggressive. For life, marine iguanas create family groups, which include one adult male and up to ten females. Young individuals are kept separately, but also stray into groups. Sometimes several families are combined into a large community.
Each male watches over his territory. Outsiders are not allowed on "family" lands. Seeing a stranger, the male warns of a violation of the border. He assumes a steady posture and begins shaking his head. If the intruder did not get out, then a fight begins. Usually strangers enter the occupied territory, having views of the "master's" harem, so the battles are serious.
Behavior in water
Marine iguanas rarely swim far from shore. In water, they make wave-like horizontal movements. Animals dive not for pleasure, but for food or to escape sharks. Male iguanas are bolder and stronger, they can afford longer swims than females. Juveniles always stay in shallow water.
What else can surprise a marine iguana? Scientists have collected interesting facts related to the blood circulation of these animals. In order not to rise often to the surface and not to expend excess energy, the reptile saves oxygen while in the water. Blood circulation slows down, only vital organs are supplied with blood. Thus, the lizard can survive under water for more than 1 hour.
What does the animal eat
Of course, the marine iguana looks very impressive and creepy, but it is not a predator. Marine iguanas are classified as herbivorous reptiles. They eat mostly It is for them that iguanas learned to dive. Some types of algae entwine coastal stones, and lizards carefully scrape them off.
reproduction
Mating games are not a favorite pastime of the male iguana. He is attracted to his harem only once a year. During this period, the male's scales become brighter, brown and reddish spots appear on it, which attract active females.
The fertilized female lays several eggs in the hole. Her clutch is small - 2-3 pieces. From above, the female sprinkles her treasure with warm sand. Fights often occur around masonry sites, since there are few sandy areas in the Galapagos, mostly the islands are composed of volcanic rock. Sometimes females destroy the clutches of rivals, making room for their offspring.
In warm sand, eggs mature for about four months. Then the young appear, which joins the parent group. In the diet of young animals there is not only vegetable, but also animal food. It is necessary for babies to grow.
Marine iguanas can hardly be called caring parents. They do not protect their offspring from predators. So most of the young become prey for gulls, snakes or dogs and cats. People try to exterminate stray dogs in order to save the number of marine iguanas, but this does not help much. Unfortunately, these animals are now classified as vulnerable species.
A few words about adaptability to life
Constant contact with salt water while swimming or eating has caused the sea lizard to develop special glands that rid it of excess salt. These salt glands are connected to the nostrils of the lizard.
Salt comes out when you sneeze. If nature did not take care of the creation of these glands, then the life span of lizards would be much shorter, since their kidneys would not be able to cope with excess salt. However, due to the fact that the species' habitat is limited only to the Galapagos, it is not well understood. There is no exact information about the life span of these lizards.