Why did the dinosaurs become extinct and how many years ago did this happen. Hypotheses about the causes of the mass extinction of dinosaurs What are your reasons for the extinction of dinosaurs

Giant lizards dominated our planet for an incredibly long time, and the reasons for their death are shrouded in mystery. Many hypotheses are put forward. But not everyone can stand up to scrutiny. One of latest versions, for example, claims that land dinosaurs were killed by butterflies.

1. Died of hunger

Breeding non-stop, gluttonous butterfly caterpillars deprived the dinosaurs of food, says Brian Switek, an American paleontologist and researcher at the New Jersey State Museum, where dinosaur bones are stored. - As a result, the lizards died out for a banal reason: from hunger.

According to Switek, 66-65 million years ago, the Earth looked like a huge flowering garden. There were no birds then, and therefore the butterflies felt at ease, multiplying tirelessly. And the caterpillars, before turning into butterflies, fed exclusively on plants - the main food of herbivorous dinosaurs. Countless armies of Lepidoptera devoured the greenery over vast expanses.

And the fewer herbivorous lizards became, the more hungry the predators were. So they all died together.

Swietek's butterfly theory added variety to a string of hypotheses that explain why dinosaurs disappeared from the face of the earth. Before him, it was believed that the lizards were killed by something larger - for example, an asteroid impact, massive volcanic eruptions, comic rays. Or our ancestors - already appeared mammals that ate eggs from dinosaurs, while themselves remained elusive for less nimble giants.

2. Eating eggs

Paleontologist George Wieland at the beginning of the 20th century argued that dinosaurs ate themselves and thereby doomed themselves to extinction. In his opinion, the ancestors of the fearsome tyrannosaurs probably took their first step towards gigantism by feeding on sauropod eggs. Even the most caring mother dinosaurs could not prevent hungry predators from poaching.

3. Deformation of the shell

Invertebrate fossil expert G. K. Erben and his colleagues also believed that eggs contributed to the extinction of dinosaurs, but not in the way described in the first paragraph. In a 1979 newspaper, researchers published a version that analysis of the composition of fragments of fossilized eggshells found in the south of France and in the Spanish Pyrenees showed two types of deviations: the shells of some eggs were multi-layered and thick, while others were extremely thin.

Either of these situations was fatal: in multi-layered eggs, the embryos would suffocate, and eggs with thin shells could easily crack and dehydrate the embryos or become easy prey for a predator.

4. Overactive glands

Paleontologist Franz Nopksa von Felso-Cilvas suggested at the beginning of the 20th century that dinosaurs grew to incredible sizes due to malfunctioning of the pituitary gland. In the end, iron was the reason that animals became pathologically huge and grotesque. Nopxa has attempted to link human pathology to the dinosaur extinction mystery, but there is no credible evidence that the pituitary gland could have influenced dinosaur size or extinction.

5. Evolutionary self-destruction

There is a theory that some species of living beings "follow the path of dinosaurs" - in other words, in the process of evolution they become too lethargic, stupid or small to survive. For a while, paleontologists thought this was exactly what happened to the dinosaurs.

6. Too many males

Fertility specialist Sherman Silber has repeatedly argued over the past decade that dinosaurs died because they couldn't find a mate.

Silber suggested that, similar to modern alligators and crocodiles, changes in outside temperature may have determined the sex of dinosaur embryos during development in eggs. In this case, climate changes caused by volcanic activity and an asteroid impact could have caused the vast majority of the eggs to hatch into males.

However, we still do not know whether or not temperature influenced the development of sexual characteristics in dinosaurs.

7. Cataract

In 1982, ophthalmologist L. R. Croft suggested that the reason for the extinction of dinosaurs was poor eyesight. With prolonged exposure to heat, cataracts develop faster, and Croft decided that dinosaurs with horns or fancy crests on their heads used these “decorations” to protect themselves from the relentless sun. mesozoic era. However, even this did not save the dinosaurs' eyes, and they eventually lost their sight before puberty.

8. Supernova

In 1971, physicist Wallace Tucker and paleontologist Dale Russell proposed that a supernova at the end of Cretaceous could have catastrophic consequences for life on Earth.

As a result of the explosion of such a supernova, the upper atmosphere of the planet was exposed to X-rays and other types of radiation, which caused rapid climate change, and the temperature on Earth began to drop rapidly, but no evidence of such an event was found.

9. Aliens

An exhibition at the Eastern Utah College Prehistoric Museum shows that the aliens could not have wiped out the dinosaurs, if only because no fossils of the aliens themselves or traces of their activities have been preserved. However, the lack of evidence has not stopped some creative people from offering similar sci-fi scenarios.

10 Farts

Another unscientific hypothesis is that dinosaurs doomed themselves to extinction with their own farts. Last year, paleontologist David Wilkinson and his colleagues tried to calculate how much gas a huge, long-necked sauropod could produce.

The researchers hypothesized that dinosaurs could have emitted enough methane to affect the global climate. But, after all, various sauropods have lived on Earth for tens of millions of years without showing any signs of gassing themselves. Ignoring actual research, Wilkinson and his colleagues gleaned evidence from thematic sites and for a long time proved the correctness of this theory.

Since November 26, the cartoon “The Good Dinosaur” has been shown in cinemas in Russia, you can read more about it in our review. In it, the giant lizards did not die out, since the ill-fated asteroid did not crash into the Earth. In reality, everything is more prosaic: the dinosaurs disappeared, and so far no one can say exactly why this happened. Disgusting men figured out the issue and offer five versions of the extinction of large lizards.

About 65 million years ago, the so-called Cretaceous-Paleogene extinction occurred - a "mass extinction" of living organisms on the surface of our planet. In addition to ordinary dinosaurs, mosasaurs, plesiosaurs, flying lizards and even mollusks with small algae have disappeared from the face of the Earth. But snakes, turtles, lizards and other reptiles, including water ones, such as crocodiles, survived. Hypotheses about what happened began to appear in the 19th century, but it is still not known for certain what it was: either an asteroid collision, or a widespread infection, or climate change.

High volcanic activity and biosphere change

The popular theory that volcanic activity may have affected the habitual life of dinosaurs is especially supported by Western scientists. Paleontologists believe that as a result of increased activity of volcanoes, the Earth's biosphere has changed: the amount of carbon dioxide in the air has greatly increased, which led to the appearance of an active greenhouse effect. Temperature lower layers atmosphere increased sharply, as evidenced by data on the outpouring of magma in about 65-68 million years ago. This led to the formation of the Deccan traps, a large igneous province in central India.

Scientists from the University of Leeds disproved this version: they simulated the artificial distribution of sulfur dioxide gases that are released during volcanic eruptions. It turned out that even with a ten-year eruption, the temperature would drop by only 4.5 degrees Celsius, which is not enough for the extinction of entire species. Also, after 50 years, the volcanoes would have died down, due to which earthly creatures, including dinosaurs, would have remained intact and unharmed in the mass.

A huge asteroid flew in and destroyed all life

Most popular in mass consciousness theory: impact event - the fall of a large celestial body to Earth, as a result of which living organisms die out on it, and a large crater remains. The validity of this hypothesis is confirmed by the presence of the latter: in the last century, the crater was discovered on the territory of the Yucatan Peninsula. The asteroid was given the name Chicxulub - it allegedly caused a giant tsunami, a sharp increase in temperature due to the release of a large amount of soil and carbon monoxide, and thereby closed light and oxygen access for living organisms.

Supporters of this assumption have linked the time of the formation of the crater - about 65 million years ago - with the date of the death of dinosaurs. In particular, this was done by the physicist Luis Alvarez and his geologist son Walter, who presented data on the parameters of the asteroid and its effect on the Earth's atmosphere as arguments. More recent evidence shows that the pair of scientists were wrong: Chicxulub flew into the planet 150,000 years before the Meso-Cenozoic collapse occurred. Also, its fall would have caused the disappearance of planktonic organisms due to the impossibility of photosynthesis, but nothing happened to them. As evidence, paleontologist Andrey Zhuravlev cites data that show that plankton quietly existed even after.

Lack of food, mass poisoning or infection

Supporters of less popular theories argue about the same thing: dinosaurs became more numerous, but there was less food and space for them. At the end of the Cretaceous period, herbivorous lizards exhausted the stocks of plants throughout the Earth, began to systematically die, and predators disappeared immediately behind them. There are also similar hypotheses that the lizards decided to eat everything and either massively poisoned themselves or stumbled upon a previously unknown infection.

The development of flowering plants

Back in 2013, it became known that flowering plants much older than scientists thought before. The found pollen existed already 240 million years ago and was older than even the most early species dinosaurs. Supporters of the hypothesis that it was the changed flowers that killed the lizards say that their abrupt evolution occurred at about the same time as the mass extinction of the dinosaurs.

As Andrei Zhuravlev, already mentioned by us, says, flowering plants began to change from the inside: the density of leaf venation increased, and they were able to survive in more severe conditions, such as lack of water. There was more poison in their tissues, they turned into productive and mass plants, gradually crowding out the rest. Due to the dominance of the flowering ones, the life of the lizards has changed: they began to poison more often, it became colder around and there was less light due to the special structure of the new, denser jungle. Birds, snakes, mammals have adapted to such conditions, but dinosaurs have not.

Dinosaurs are dead! This is perhaps the only fact about them that all scientists agree on. But regarding the reasons for the disappearance of giant lizards, disputes are still ongoing. The popular opinion is that their mass death was caused by the collision of a giant asteroid with the Earth. However, there are many other interesting proposals that may complement the generally accepted theory or consider alternative views. Today we will talk about why dinosaurs became extinct.

When did the dinosaurs go extinct?

It should be noted that the extinction was not instantaneous, as some films and TV shows usually present to us. Even if we start from the theory of the collision of the Earth with an asteroid, then after that all the dinosaurs did not die immediately, but the process had already been launched ...

The extinction began at the end of the so-called "cretaceous period"(about 250 million years ago) and lasted about 5 million years (!). During this period, many species and plants disappeared.

However, dinosaurs have been the dominant species on Earth for quite a long time - about 160 million years. During this period, new species disappeared and appeared, dinosaurs evolved, adapted to climate change and were able to survive several mass extinctions, until something happened that led to their gradual and final death.

For reference: Homo sapiens lives on Earth for only 40 thousand years.

Who survived the extinction?

Climate change on Earth during the Cretaceous period reduced the diversity of life, but the descendants of many of the then species today delight us with their presence. These include crocodiles, turtles, snakes and lizards.

Mammals also did not suffer much, and after the complete extinction of the dinosaurs, they were able to take a dominant position on the planet.

One might get the impression that the death of living beings on Earth was selective, and that precisely those conditions were formed in which dinosaurs could not survive. At the same time, the rest of the species, although severely affected, could continue to exist. These thoughts greatly excite the minds of admirers of various conspiracy theories.

By the way, the word "dinosaur" with Greek Literally translated as "terrible lizard".

Versions of the extinction of dinosaurs

To date, it is still not known for certain what exactly killed the dinosaurs. There are many hypotheses, but evidence is not enough. Let's start with the asteroid version, which has been greatly popularized and largely distorted by the media and filmmakers.

Asteroid

Mexico has the Chicxulub crater. It is believed that it was formed precisely after the fall of that ominous asteroid that provoked the mass extinction of dinosaurs.

The asteroid itself caused enormous destruction in the area of ​​its fall. Almost all life in this area was destroyed. But the rest of the inhabitants of the Earth suffered from the consequences of the fall of this cosmic body. A powerful shock wave passed through the planet, clouds of dust rose into the atmosphere, dormant volcanoes woke up, the planet was enveloped in dense clouds that practically did not let in sunlight. Accordingly, the amount of vegetation, which was a source of food for herbivorous dinosaurs, decreased several times, and they, in turn, allowed predatory dinosaurs to survive.

By the way, there is an assumption that at that time two celestial bodies fell on our planet. At the bottom indian ocean a crater was found, the appearance of which dates back to the same time.

Fans of everything to refute cast doubt on this hypothesis. In their opinion, the asteroid was not large enough to trigger a series of cataclysms. In addition, both before this event and after, other similar space bodies collided with the earth, but they did not provoke mass extinctions.

The version that this asteroid brought microorganisms to the planet that hit the dinosaurs also takes place, although not so likely.

cosmic radiation

Continuing the theme of the fact that it was space that killed all the dinosaurs, it is worth considering the assumption that this led to burst of gamma rays close to solar system. This happens as a result of a collision of stars or a supernova explosion. The flow of gamma radiation damaged ozone layer our planet, which led to climate change and mutations.

Volcanic activity

We have already mentioned that the asteroid could provoke the awakening of dormant volcanoes. But this could happen without his participation, and the consequences would still be sad.

A significant increase in volcanic activity has led to the fact that ash in the atmosphere partially limited the flow sunlight . And then - the onset of volcanic winter, a decrease in the number of plants and a change in the composition of the atmosphere.

Skeptics and in this case have something to say. Many scientists believe that the changes caused by abnormal volcanic activity were gradual, and dinosaurs had a high ability to adapt, which helped them survive the flooding kind of vagaries of nature. So why couldn't they adapt this time? A question without an answer.

A sharp decline in the level of the World Ocean

This concept is called "Maastricht regression". The only connection of this event with the extinction of the dinosaurs can be traced to the fact that everything happened at about the same period. In addition, previous great extinctions were sometimes accompanied by changes in water levels.

Food problems

There are two options: either due to climate change, the dinosaurs simply could not find enough food for themselves, or plants appeared that killed the dinosaurs. It is believed that the Earth spread flowering plants containing alkaloids, which poisoned the dinosaurs.

Change of magnetic poles

This phenomenon happens periodically on our planet. The poles change places, but the Earth remains for a while without magnetic field . Thus, the entire biosphere becomes defenseless against cosmic radiation: organisms die or mutate. And it can go on for thousands of years.

Continental drift and climate change

This hypothesis tells that dinosaurs, for some reason, could not survive the climate changes that were caused by the drift of the continents. Everything happened quite prosaically: temperature jumps, the death of plants, the drying up of rivers and reservoirs. Obviously, the movement of tectonic plates was accompanied by increased volcanic activity. The poor dinosaurs were simply unable to adapt.

Interestingly, rising temperatures may have affected the formation of dinosaurs in the egg. As a result, only cubs of the same sex could hatch. A similar phenomenon is observed in modern crocodiles.

Epidemic

Insects preserved in amber can tell scientists a lot of interesting things about ancient times. In particular, it was found that many dangerous infections began to appear precisely during the extinction of dinosaurs.

We already know that dinosaurs could adapt to climate change, but their underdeveloped immune systems could not protect them from a deadly disease.

Theory of controlled evolution

It should immediately be noted that this theory is popular in conspiracy circles. These guys believe that some other mind is using our planet as a platform for experiments. Probably this "intelligence" on the example of dinosaurs studied the features of evolution, but it's time to clear the experimental site in order to start the same research, but with mammals in the lead role.

Thus, extraterrestrial intelligence immediately clears the Earth of dinosaurs and begins new stage experiment, the main object of which is we - people! Some kind of REN-TV. But it’s worth recognizing that conspiracy theorists skillfully present everything and refute other theories well.

Dinosaurs vs Mammals

Small mammals could easily destroy the toothy giants. Scientists do not exclude fierce competition between them. Mammals proved to be more advanced in terms of survival, it is easier for them to get food and adapt to the environment.

The main advantage of mammals was the difference between their mode of reproduction and that of dinosaurs. The latter laid eggs, which it was not always possible to protect from the same small animals. Besides little dinosaur required a huge amount of food to grow to the right sizes and food became more and more difficult to obtain. Mammals were born in the womb, fed with mother's milk, and then did not need too much in large numbers food. Especially under the nose were always dinosaur eggs, which could be imperceptibly credited.

Coincidence of factors

Many scientists tend to believe that one should not get hung up on any one reason, because dinosaurs were very tenacious and withstood many surprises from nature over millions of years. Most likely, climate change, food problems, and competition with mammals are to blame. It is possible that the asteroid has become a kind of control shot. All this combined formed exactly those conditions in which dinosaurs could not survive.

Does extinction threaten humans?

Dinosaurs have lived on Earth for millions of years, humans for only a few tens of thousands. During this relatively short period, we were able to create a reasonable society. But it hardly protects us from extinction.

There are quite a large number of versions of the disappearance of mankind, ranging from global catastrophes and epidemics, and ending with the same cosmic threat in the form of asteroids and star explosions. However, people today can easily cease to exist - stocks nuclear weapons there is more than enough on Earth for these purposes ... True, some people can still be saved if we have time

And lots of small algae. In total, 16% of families of marine animals (47% of genera of marine animals) and 18% of families of terrestrial vertebrates perished.

Presumably some dinosaurs (triceratops, theropods, etc.) existed in the west North America and in India for a few more million years at the beginning of the Paleogene, after their extinction elsewhere.

The most famous versions of the extinction of dinosaurs

Astrophysical

Geophysical and climatic

Evolutionary biological

1. Dinosaurs could not adapt to the change in vegetation type and became poisoned by the alkaloids contained in the flowering plants that emerged.
2. Dinosaurs were exterminated by the first predatory mammals, destroying the clutches of eggs and cubs.

Disadvantages of hypotheses

Speaking about the reasons for the extinction of the dinosaurs themselves, it is necessary to note some important features of this extinction:

• The extinction can only be called “rapid” by geological standards, while most paleontologists believe that in reality it took at least several hundred thousand years.
• In general, talking about the "rapid extinction of dinosaurs" is not entirely correct. In any group of living beings, the formation of new species and the extinction of previously existing ones are constantly going on. These processes go on simultaneously, and if the rates of extinction and the formation of new species are equal, the group exists. From this point of view, during the period of the "great extinction", the rate of extinction dinosaurs (precisely dinosaurs, with marine reptiles the picture looks different), that is, the extinction of pre-existing species does not exceed the rate of extinction in previous periods. But the extinct species of dinosaurs were not replaced by new ones, as a result of which the group, in the end, completely died out.

In fairness, it should be noted, however, that this point of view is not shared by all experts.

As a result, the main problems of the listed versions are as follows:

• The hypotheses focus on extinction, which, according to some researchers, went at the same pace as in the previous time.
• Some of the hypotheses have insufficient factual evidence. Thus, no traces have been found that the reversals of the Earth's magnetic field affect the biosphere; there is no conclusive evidence that the Maastrichtian regression in world sea levels could have caused a mass extinction of this magnitude; there is no evidence of sharp jumps in ocean temperature during this period; nor is it proven that the catastrophic volcanism that produced the Deccan traps was widespread, or that its intensity was sufficient to cause global climate and biospheric changes.
• All impact hypotheses (impact hypotheses), including astronomical ones, do not explain the selectivity of extinction (why certain organisms survived when others died) and do not correspond to the estimated duration of its period (many groups of animals began to die out long before the end of the Cretaceous). The transition of the same ammonites to heteromorphic forms also indicates some kind of instability. It may very well be that many species have already been undermined by some long-term processes and stood in the way of extinction, and the catastrophe simply accelerated the process.

On the other hand, it should be borne in mind that the duration of the extinction period cannot be accurately estimated due to the Signor-Lipps effect associated with the incompleteness of paleontological data (the time of the burial of the last fossil found may not correspond to the time of the extinction of the taxon).

"Biospheric" version

A biospheric version of the "great extinction" is popular in Russian paleontology, including the extinction of the dinosaurs. According to her, the main initial factors that predetermined the extinction of dinosaurs were:

1. The emergence of flowering plants;
2. Gradual climate change caused by continental drift.

The sequence of events that led to extinction is presented as follows:

• Flowering plants with a more developed root system and better use of soil fertility, rather quickly replaced other types of vegetation everywhere. At the same time, insects appeared that specialized in feeding on flowering plants, and insects “attached” to pre-existing types of vegetation began to die out.
• Flowering plants form sod, which is the best of natural erosion suppressors. As a result of their spread, the erosion of the land surface and, accordingly, the entry into the oceans has decreased. nutrients. "Impoverishment" of the ocean with food led to the death of a significant part of algae, which were the main primary producer of biomass in the ocean. Along the chain, this led to the complete disruption of the entire marine ecosystem and caused mass extinctions in the sea. The same extinction also affected the large flying lizards, which, according to existing ideas, were trophically associated with the sea. Some of the large marine reptiles, in addition, could not withstand competition with the sharks of the modern type that appeared at that particular time.
• On land, animals actively adapted to feeding on green mass (by the way, herbivorous dinosaurs Same). Small phytophagous mammals (like rats) appeared in the small size class. Their appearance led to the appearance of the corresponding predators, which also became mammals. Small-sized mammalian predators were not dangerous for adult dinosaurs, but fed on their eggs and cubs, creating additional difficulties for dinosaurs in reproduction. At the same time, the protection of offspring for a dinosaur is practically impossible due to too big difference in adult and juvenile sizes.
• As a result of the drift of the continents at the end of the Cretaceous, the system of air and sea currents changed, which led to some cooling on a significant part of the land and an increase in the seasonal temperature gradient. Inertial homoiothermy, which provided dinosaurs with an evolutionary advantage in previous periods, no longer had an effect under such conditions.

As a result of all these reasons for dinosaurs, unfavourable conditions which led to the cessation of the emergence of new species. The "old" species of dinosaurs existed for some time, but gradually died out completely. Apparently, there was no fierce direct competition between dinosaurs and mammals; they occupied different size classes, existing in parallel. Only after the extinction of the dinosaurs did mammals capture the vacated ecological niche, and even then not immediately.

Curiously, the development of the first archosaurs in Triassic period, was accompanied by the gradual extinction of many therapsids, the highest forms of which were essentially primitive egg-laying mammals.

Disadvantages of the biospheric version

In the above form, the version uses hypothetical ideas about the physiology and behavior of dinosaurs, does not compare all the changes in climate and currents that took place in the Mesozoic to those that took place at the end of the Cretaceous, does not explain the simultaneous extinction of dinosaurs on continents isolated from each other, does not explain the selectivity of the claimed effects of mammalian evolution on other vertebrates.

Sources and notes

Links

• The impact theory of mass extinction The Impact Theory of Mass Extinction )
• Reflections on the "rare event" and related representations in geology

By the end of the Cretaceous animal world sushi reached great diversity, and its representatives were perfectly adapted to life in an even and favorable climate this era. However, disaster was not far off.

Based on the fossilized remains of two dinosaurs, the artist restored the painting deadly fight a small predatory velociraptor (Velociraptor) and a shell-covered protoceratops (Protoceratops).

Typical herbivores of that time were also hadrosaurs, or duck-billed dinosaurs - bipedal reptiles ranging in size from medium to giant, which, if necessary, could move on four limbs. They got their name because of the wide, flat, toothless beaks, outwardly resembling the beaks of modern ducks. Functionally, however, their beaks were intended for biting off large plant shoots. On the upper and lower jaws of gasdrosaurs, behind the beak, about 2 thousand teeth were located in several rows, well adapted to grinding hard plant foods.

As large, bipedal herbivores, hadrosaurs such as Edmontosaurus (Edmontosaurus) replaced the initially even more successful Iguanodon during the Middle and Late Cretaceous.

Variety of predators

There were many types of dromoesaurus various forms and sizes. They probably knew how to camouflage well in the forests of the Cretaceous period. Long legs and prehensile forelimbs with large curved claws are clear evidence of their predatory nature.

The lower part of the "size scale" in predators at that time was occupied by dromaeosaurids (literally - "running lizards"). This group included several types of dinosaurs, from small dromaeosaurs the size of a turkey to 6-meter Utahraptors (Utahraptor). Dromaeosaurs were "highly specialized" predators. Their distinguishing feature- large and extremely sharp claws of the second toes. In order not to become dull on the ground during movement, these fingers were always straightened. A long tail with a large number of bony rods along almost the entire length helped to maintain balance while running.

They caused fear

Dromaeosaurs occupied an ecological niche similar to cheetahs in the ecosystems of modern Africa. It is believed (although not proven) that they hunted in packs. Their prey probably included small hypsilophodonts and thescelosaurs, as well as hadrosaurs and other young reptiles more large species. Carnivores that occupied the middle of the scale, such as Chilantaisaurus from the Allosaurus family, most likely preyed on ceratopsians and medium-sized hadrosaurs. The largest land predators of this era (and all others, including our time) were tyrannosaurids.

In the late Cretaceous, tyrannosaurids included many different species. For example, the skull of the "small" (about 7 m long7) tyrannosaurid Alioramus from Mongolia was long and low, more like that of a crocodile, while the most famous member of this family, the tyrannosaurus rex (Tyrannosaurus rex), had a tall, massive skull. The "predatory specialization" of the tyrannosaurus took a special path: the forelimbs of this 12-meter monster decreased so much that they did not even reach its lower jaw. Their function is still a matter of conjecture, but it is clear that they were not used to capture prey. For this, the beast was served by its huge skull with a movable upper jaw. Having overtaken the victim, the tyrannosaurus put all its strength into a headbutt; movable cranial joints, like shock absorbers, softened the impact reaction. Tyrannosaurus prey was almost certainly large herbivorous lizards, too large and dangerous for smaller theropods. According to estimates, adult tyrannosaurs weighed up to 7 tons and, reaching a height of 5 m with a body length of up to 12-15 m, occupied an ecological niche, which, due to their size, has no analogue in the modern fauna.

egg thieves

This ornithomimus (Ornithomimus - “imitator of birds”) was the size of a modern ostrich, but, unlike it, had long tail to help maintain balance while running. This creature may well have eaten eggs, but some researchers believe that it was a herbivore.

In the case of Oviraptor (the "egg thief"), similar external factor food similar to the diet of modern parrots can serve: nuts, plant seeds, fruits, eggs, although, most likely, oviraptors also ate small animals - reptiles and mammals.

Swift, modern ostrich-like ornithomimids and bipedal, dog-sized troodontids likely fed on small, defenseless animals and, together with other theropods mentioned, made up the variety of carnivorous reptiles of the Late Cretaceous.

herbivorous crocodiles

In the late Cretaceous period, part of their numerous species were animals that we could hardly call crocodiles. Perhaps the most unusual among them was a small creature, the remains of which struck science community in June 2000 Named simosuchus (Simosuchus - "chicken-nosed crocodile"), it was discovered in the Late Cretaceous deposits of Madagascar. This crocodile was a very unusual ANIMAL: its skull is extremely short (in most crocodiles, the muzzle is three times longer than the rest of the skull, and in the simosukh these parts of the skull are almost equal). The front of the muzzle was almost flat. Lower jaw, unlike the rest of the crocodile, was connected to the skull in its front, and not in the back of the head. The flat, leaf-shaped teeth, with small cusps at the edges of the square jaws, more closely resemble the teeth of ankylosaurs. In many ways, the head of the Simosuchus is also more like that of an ankylosaurus or tortoise, which it also resembled in its short, shelled torso. Some features of its anatomical structure suggest that it could dig the ground well, but swam in a completely different way than modern crocodiles swim.

Movement of the continents

We are not aware of ankylosaur remains from South America or Africa, and the reason for their absence on these continents is the configuration of the continents at the end of the Mesozoic. Ankylosaurs appeared in the Northern Hemisphere, apparently, some time after the southern and northern parts of the ancient protocontinent of Pangea parted, and therefore could not get to the southern continent, already separated from the northern one by a vast expanse of water.

The presence of Simosuchus in Madagascar is in good agreement with the findings of several rare species fossil crocodiles with a similar anatomical structure. One of them, Uruguayasuchus from Uruguay, is very similar to the simosuchus. The proximity of the structure indicates the origin from the same evolutionary trunk, and since Uruguayasuchus comes from South America, the discovery of the remains of simosukhus in Madagascar confirms its connection in the Late Cretaceous with South America(through Africa). In terms of evolution, the crocodilians were an incredibly successful group of reptiles. They even survived the mass extinction of species at the end of the Cretaceous, when dinosaurs completely disappeared from the face of the Earth.

Dinosaur extinction

There are a number of theories that explain this extinction: one of them is the collision of the Earth with a huge asteroid about 65 million years ago. Evidence of such a collision is a crater with a diameter of 110 km on seabed near the Mexican Yucatan Peninsula, formed at this time. Here they find pieces of quartz, called "impact": it has a unique crystal structure, characteristic only for quartz from the places where nuclear explosions. And a layer of sediments containing iridium (a rare metal on Earth that is part of many asteroids) has been found in rocks of this age around the world. The very process of extinction of dinosaurs continues to cause heated debate.

Track meteor shower, possibly causing the so-called. "global winter" that dinosaurs could not survive.

• Did you know?
• Some paleontologists and geologists believe that the most powerful volcanic eruptions over several millennia at the end of the Cretaceous, during which a huge amount of volcanic gas and dust were released into the atmosphere, caused global climate change, causing the extinction of dinosaurs. The place of these eruptions in India is called the Deccan Traps (the northwestern part of the Deccan Plateau).
• According to some paleontologists, dinosaurs had a much higher metabolic rate than modern reptiles, and therefore they needed so much energy from food that they could not endure food shortages during the “global winter” that came to Earth after a collision with an asteroid.
• Before the asteroid impact, the world was like a greenhouse with constant warm climate. However, this was not the greenhouse that, under the influence of man, could arise in the 21st century, since the climate in that era had developed over the previous millions of years and was even and stable.