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Giant Reptiles of the Mesozoic seas

Temnodontozavr, who lived about 200 million years ago, had the eyes of a unique size. Their diameter was equal to 26 centimeters for almost two-meter size of the skull of this dinosaur.

 Thanks to the discoveries of recent years the study of marine reptiles of the Mesozoic, a long time remained in the shadow of their distant relatives of land - the dinosaurs, is experiencing a real renaissance. Now we can quite confidently reconstruct the appearance and habits of the giant aquatic reptiles - ichthyosaurs, pliozavrov, mozazavrov and pleziozavrov.Skelety aquatic reptile known to science were among the first, played an important role in establishing the theory of biological evolution. Massive jaw mozazavra found in 1764 in a career in the Dutch city of Maastricht, clearly confirms the extinction of animals, which at that time was radically new idea. And at the beginning of the XIX century finds skeletons ichthyosaurs and plesiosaurs, made Mary Enning in southwest England, was given a wealth of material for research into the still emerging science of extinct animals - paleontologii.V nowadays marine species of reptiles - crocodiles, brine, sea snakes and turtles and lizards, iguanas, Galapagos - are a fraction of reptiles inhabiting the planet. But in the Mesozoic era (251-65 million years ago), their number has been incomparably greater. This, apparently, favored a warm climate that allowed the unfit to maintain a constant body temperature of the animals feel great in the water - a medium high heat capacity. In those days, marine reptiles scoured the sea from pole to pole, occupying the ecological niches of our contemporary whales, dolphins, seals and sharks. For more than 190 million years, they were "caste" of top predators, hunting is not just for fish and cephalopods, but also each other.
Kronozavr was horrified seas Cretaceous era (125-99 million years ago), and one of the largest marine reptiles of all time. His name was given in honor of Kronos - one of the ancient Titans.
Again in water

As well as aquatic mammals - whales, dolphins and pinnipeds, marine reptiles evolved from terrestrial air-breathing ancestors: 300 million years ago the reptiles conquered land, failing due to the appearance of eggs protected by leathery shells (in contrast to frogs and fish), to move from breeding water to breed out of the water environment. Nevertheless, for one reason or another one or the other group of reptiles in different periods again "tried to happiness" in the water. Pinpoint those causes is not yet possible, but as a rule, the development of a new kind of niche to explain its unemployment, the presence of food resources and lack of predators.

Currently invading lizards in the ocean began when the biggest in the history of our planet permskotriasovogo extinction (250 million years ago). On the causes of this disaster experts argue so far. Put forward different versions: the fall of a large meteorite, intense volcanic activity, massive release of methane hydrate and carbon dioxide. One thing is clear - the extremely short by geological standards, the time period from the variety of species of living organisms do not become a victim of environmental catastrophe was only every twentieth. Abandoned warm seas provides "colonialists" great opportunities, and perhaps that is why in the Mesozoic Era came several groups of marine reptiles. Four of them in number, diversity and distribution of truly had no equal. Each of the groups - ichthyosaurs, plesiosaurs and their relatives pliozavry and mozazavry - consisted of a predator, occupying the top of the food pyramid. And each group generated Giants truly monstrous proportions.

The most important factor in the successful development of Mesozoic reptiles of the aquatic environment, served as a transition to a live birth. Instead of laying eggs, the females give birth to fully formed and very large babies, thereby increasing their chances of survival. Thus, the life cycle of reptiles, which is in question here, now held entirely in the water, and the last thread connecting the marine reptiles from the land, was torn. In the future, apparently, it is an evolutionary acquisition has allowed them to leave the shallows and conquer the open sea. No need to go to the bank lifted restrictions on size, and some of the marine reptiles have benefited from gigantism. Grow large - is not easy, but if it grew - try to overpower this. Anyone hurt himself.
Shonizavr - the largest marine reptile in the history of evolution, the age of which exceeds 200 million years. A whopper weighed 40 tons. Probably the food she served as a small schooling fish and squid.
Ichthyosaurs - longer, deeper, faster

Ancestors ryboyascherov-ichthyosaurs, who have mastered the aquatic environment about 245 million years ago, there were medium-sized inhabitants of shallow waters. Their bodies were not barrel-shaped, as in the offspring, and elongated, and its deformation played a significant role in the motion. However, over 40 million years the appearance of ichthyosaurs changed significantly. Initially elongated body has become more compact and perfectly streamlined, and caudal fin with a large lower lobe and a small top of most species evolved in an almost symmetrical.

On kinship ichthyosaurs paleontologists have only guessed at. It is believed that this group of very early evolutionary split from the trunk, then gave the branch of reptiles such as lizards and snakes and crocodiles, dinosaurs and birds. One major problem remains the lack of transitional link between the terrestrial ancestors of ichthyosaurs and primitive marine forms. The first known science ryboyaschery - it is completely aquatic organisms. What was their ancestor, yet difficult to say.
The length of the neck elasmozavrov who lived 100 million years ago, often exceeded the total length of its body and tail. The neck was their main tool to hunt for fish and cephalopods.

The length of most ichthyosaurs did not exceed 4.2 meters. However, there were also giants, which reached 21 meters. These whopper included, for example, shonizavry who lived in the late Triassic period about 210 million years ago. This is one of the biggest sea animals that ever lived in the oceans of our planet. In addition to the huge size of these ichthyosaurs is very different from a long skull with narrow jaws. To imagine shonizavra as a joke, an American paleontologist, it is necessary to inflate a huge rubber dolphin and elongated his face and fins. The most interesting thing is that only young animals had teeth, whereas gingival adult reptiles were toothless. You may ask: how could eat such colossi? To this we can reply: if shonizavry were smaller, then one would assume that they were chasing prey and swallowed it whole, as do the sword-fish and its relatives - Marlin and sailboats. However, high-speed Dvadtsatimetrovy giants could not be. Perhaps they are saturated with a small gregarious fish or squid. There is also an assumption that adults shonizavry used filtration device such as baleen, which allowed them to run off of water plankton. By the beginning of the Jurassic period (200 million years ago) in the sea forms of ichthyosaurs appeared on their bet on the speed. They skillfully chased fish and rapid belemnites - extinct relatives of squids and cuttlefish. According to modern calculations, three-, four-meter ichthyosaur stenopterigius developed a cruising speed of not less than one of the fastest fish, tuna fish (dolphins swim twice as slow) - nearly 80 km / h or 20 m / s! In the water! The main driver of such champions as a powerful tail with vertical blades, a fish.

In the Jurassic period, which became the golden age of ichthyosaurs, these lizards were the most numerous marine reptiles. Some types of ichthyosaurs in search of prey could dive to a depth of half a kilometer or more. Distinguish between moving objects at a depth of these reptiles could because the size of their eyes. So, temnodontozavra eye diameter equal 26 centimeters! More (up to 30 inches) - only the giant squid. Of strain during fast motion or at great depth eyes ichthyosaurs protected the kind of eye skeleton - bearing a ring consisting of more than a dozen bony plates that develop in the shell of the eye - sclera.

Elongated face, narrow jaw and tooth shape ryboyascherov indicate that they were fed, as already stated, with respect to medium-sized animals: fish and cephalopods. Some types of ichthyosaurs had pointed conical teeth that were good to miss nimble, slippery prey. In contrast, other ichthyosaurs teeth were broad, with blunt or rounded tops to crush shells of cephalopods such as ammonites and nautilidy. But not so long ago was discovered the skeleton of a pregnant female ichthyosaur, within which other than fish bones found bones of young sea turtles, and that most amazing of all, the bone of the ancient sea-bird. There is also a message and the detection of residues in the belly of ryboyaschera pterosaur (flying reptile). This means that a diet ichthyosaurs were significantly more diverse than previously thought. Moreover, one discovered in this year of early ryboyascherov who lived in the Triassic (about 240 million years ago), on the edge of the rhombic cross-section of the teeth were serrated, indicating that its ability to detach from production pieces. Dangerous enemies have such a monster, reaches a length of 15 meters, almost was not. However, this branch of evolution for unclear reasons, cut short in the second half of the Cretaceous period 90 million years ago.
In the bones tilozavrov who lived 90-65 million years ago, showed signs of necrosis. Typically, these pathologies are characteristic of animals that sink to great depth.
Plesiosaurs and pliozavry - unlike relatives

In the shallow waters of the seas Triassic period (240-210 million years ago), flourished, another group of reptiles - notozavry. By way of life they most resembled modern seals, spending the time on the beach. For notozavrov was characterized by an elongated neck, and they sailed through the tail and webbed feet. Gradually, some of them have replaced the clutches in the fins, which are used as oars, and the more powerful they were, in order to weaken the role of the tail.

Notozavry considered the ancestors of plesiosaurs, which the reader knows the legend of the monster of Loch Ness. The first plesiosaurs appeared in the mid-Triassic (240-230 million years ago), but the beginning of flowering occurs at the beginning of the Jurassic period, about 200 million years ago.

Then there were and pliozavry. These marine reptiles were close relatives, but they looked different. Representatives of both groups - a case unique among aquatic animals - moving with the help of two pairs of large vesloobraznyh fins, and their movements were probably not unidirectional and multidirectional: when the front fins were moving down, back - up. Also, we can assume that most were used only finfish front blade - so save more energy. The rear is connected to work only during the surge in production or escape from larger predators.

Plesiosaurs are easily recognizable by a very long neck. For example, in elasmozavra it consisted of 72 vertebrae! Scientists know even the skeletons of the neck which is longer than the body and tail combined. And, apparently, that his neck was their advantage. Let plesiosaurs were not the fastest swimmers, but the most agile. By the way, with the disappearance of their long-necked animals in the sea no longer appears. And another interesting fact: the skeletons of some plesiosaurs not found in the sea and in estuaries (where rivers flow into the sea) and even freshwater sediments. Thus, it is clear that this group does not dwell solely in the seas. Over time it was thought that plesiosaurs were fed mainly on fish and cephalopods (belemnites and ammonites). Lizard slowly and quietly swam to the bottom of the pack behind and thanks to its super long neck snatch prey prominently on the background light of the sky before a flock rushed to their heels. But today it is obvious that the diet of these reptiles was richer. In the found skeletons of plesiosaurs often smooth stones, probably specifically swallowed lizard. Specialists believe that this was not the ballast, as previously thought, but very real millstones. Muscular stomach of the animal, cutting, move these stones, and they razdavlivali strong shells of mollusks and crustaceans caught in the womb of plesiosaur. Skeletons of plesiosaurs with the remnants of benthic invertebrates suggest that in addition to species, specializing in hunting in the water column, there were those who preferred to swim near the surface, collect booty from the bottom. It is also possible that some plesiosaurs could move from one type of food to another, depending on its availability, because the long neck - it's a great "fishing rod" with which it was possible to "catch" the most different prey. It is worth adding that the neck of these predators was quite robust, and sharply bend, or lift it out of the water they could not. This, incidentally, casts doubt on many stories about the Loch Ness monster, when witnesses reported seeing it a long neck protruding from the water. The largest of plesiosaurs - a New Zealand mauizavr reaches 20 meters in length, almost half of which was a huge neck.

First pliozavry who lived in the late Triassic and early Jurassic period (about 205 million years ago), much like their relatives, plesiosaurs, initially misleading paleontologists. The heads of them were relatively small, and neck - is quite long. Nevertheless, by mid-Jurassic period differences were very significant: the main trend of their evolution has been an increase in head size and power of the jaws. Neck, respectively, was short. And if the plesiosaurs were hunted mainly for fish and cephalopods, adult pliozavry chasing other marine reptiles, including plesiosaurs. By the way, carrion, they did not strain.

The largest of the first was a seven-pliozavrov romaleozavr, but its dimensions, including the size of his meter jaws, pales when compared with the monsters that emerged later. The oceans of the second half of the Jurassic period (160 million years ago) held sway lioplevrodony - monsters arrives, perhaps 12 meters in length. Later in the Cretaceous period (100-90 million years ago), lived the Colossi of similar size - and kronozavry brahauheniusy. However, most have been huge pliozavry Late Jurassic period.
Lioplevrodony inhabiting the depths of the sea 160 million years ago, could move quickly through large flippers, which they waved like wings

In recent years, paleontologists unspeakably lucky to have a sensational discovery. So, two years ago, a Norwegian expedition led by Dr. Jørn Khurum extracted from the permafrost on the island of Spitsbergen fragments of the skeleton of a giant pliozavra. Its length calculated by one of the cranial bones. Turned out to be - 15 feet! And last year in the Jurassic deposits of the county of Dorset in England, scientists waited for another stroke of luck. At one of the beaches of Weymouth Bay local collector of fossils, Kevin Sheehan dug almost entirely preserved skull of a huge size of 2 meters 40 centimeters! The length of this "sea dragon" could be as much as 16 meters! Almost the same length was a young lady pliozavra found in 2002 in Mexico and named the Monster of Aramberri.

But that's not all. In the Museum of Natural History, University of Oxford kept a giant mandible pliozavra-makromerusa whose size is 2 meters 87 centimeters! Bone is damaged, and it is believed that its total length was no less than three meters. Thus, its owner can reach 18 meters. Truly imperial proportions.

But pliozavry were not just big, they were real monsters. If anyone is endangering them, only themselves. Yes, huge, like a whale ichthyosaur-and long-necked plesiosaur shonizavr-mauizavr were longer. But the huge predators pliozavry were perfect "killing machine" and had no equal. Three-meter monster fins rapidly carried to the goal. Powerful jaws with a palisade of large teeth the size of a banana crumbled bones and torn flesh of the victims, regardless of their size. They truly were invincible, and if anyone and can be compared with them in power, so this fossil shark-megalodona. Tyrannosaurus rex beside giant pliozavrami looks like a pony in front of the Dutch heavy trucks. Taking for comparison the modern crocodile, paleontologists have calculated the pressure that developed jaws of a huge pliozavra at the bite: it turned out, about 15 tons. The notion of power and appetite penalty kronozavra, who lived about 100 million years ago, scientists have been, "looking" in his belly. There they found the bones of plesiosaur.

Throughout the Jurassic and most of the Cretaceous plesiosaurs and pliozavry were dominant ocean predators, although we should not forget that nearby were always sharks. Anyway, the big pliozavry became extinct about 90 million years ago, for unclear reasons. However, as we know, a holy place is never empty. To replace them in the seas of the late Cretaceous period, there were giants that could compete with the most powerful of pliozavrov. We are talking about mozazavrah.

Mozazavr mozazavru - lunch

Group mozazavrov, replacing, and perhaps superseded pliozavrov and plesiosaurs, emerged from the evolutionary branch that is close to the monitor lizards and snakes. I totally clicked to life in water and become viviparous mozazavrov replaced the clutches in the fins, but the main driver was a long flattened tail, and in some species it ended in a fin like a shark. It may be noted that, according to the pathological changes found in fossilized bones, some mozazavry know how deep to dive, and like all the extreme divers suffering from the effects of such immersions. Some species mozazavrov bottom feeders, crushing mollusk shells with short broad teeth with rounded tops. However, conical and slightly curved back terrible teeth of most species leave no doubt in the food preferences of their owners. They hunted fish, including sharks, cephalopods, crushing shells of turtles, seabirds swallow, and even flying dinosaurs, tearing apart other marine reptiles and each other. So, inside the penalty tilozavra were found semidigested plesiosaur bones.

The design of the skull mozazavrov allow them to swallow whole, even very large prey: like snakes, their lower jaw had been equipped with advanced joints, and some bones of the skull articulated movable. As a result of wide-open mouth was a truly monstrous proportions. Moreover, it is in heaven grew two extra rows of teeth that allowed stronger hold prey. But do not forget that mozazavrov also hunted. Paleontologists have found five-meter tilozavra was crushed skull. The only one who could do such a thing, so this is another, larger mozazavr.

For 20 million years mozazavry rapidly evolved, giving the giants, the mass and size comparable with the 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 the dinosaurs and pterosaurs. Possible reasons for a new environmental disaster might strike a huge meteorite and (or) increased volcanic activity.

First, even before the Cretaceous extinction, disappeared pliozavry somewhat later - the plesiosaurs and mozazavry. It is believed that this occurred because of violations of food chains. Triggered domino effect: the mass extinction of some groups of unicellular algae has led to the disappearance of those who ate them - crustaceans, and as a consequence, fish and cephalopods. Marine reptiles were on top of the pyramid. Extinction mozazavrov, for example, could be a consequence of extinction of ammonites that form the basis of their diet. Nevertheless, the final clarity on this issue there. For example, two other groups of predators, sharks and bony fish also feed on ammonites survived the extinction of the Late Cretaceous era with relatively little loss.

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