Dinosaurs are ancient creatures that appeared on the planet about 225 million years ago. For 160 million years, these animals dominated the planet. The extinction period took about 5 million years, and now for about 65 million years in the animal world, they are absent. There are many hypotheses why dinosaurs disappeared. How these animals became extinct and ceased to exist, we will tell in our article.
The appearance of dinosaurs
Planet Earth was inhabited by different species of plants and animals 3 billion years ago. In the process of evolution, plants and animals appear and disappear, and each such process has its own time interval and period. Dinosaurs on the planet lived in the Mesozoic era - these are the Triassic, Jurassic and Cretaceous periods.
The first simplest plants were seaweed, and the first animals were small marine mollusks. The appearance of fish occurred approximately 500 million years ago. About 370 million years ago, the first animals, amphibians, went on land. Reptiles are a new group of animals that appeared about 300 million years ago. The animals had scaly skin, they could lay eggs and be constantly on land. The next in the chain of evolution were dinosaurs. Extinct animal species gave impetus to the development of such a science as paleontology.
Dinosaur description
One of the amazing animals that lived on the planet are dinosaurs. How these large animals died out and how they lived can only be judged by the petrified remains. From the fossil remains, we can conclude that they were reptiles, like crocodiles, lizards, turtles and snakes. The size of dinosaurs varies in a wide range - from tiny to giants. They possessed four limbs and a tail. Dinosaurs stood and moved on straight limbs, some on their hind legs, others on all four, and others could move on both two and four limbs. Many dinosaurs had long necks and teeth. Their habitat was significant, but 65 thousand years ago they suddenly became extinct.
Dinosaurs are divided into two groups: lizardotazovye and poultry. The difference between the groups is the structure of the bones of the pelvis. In the lizards and pelvic dinosaurs, the structure of the pelvis is four-beam, and in the poultry-type dinosaurs - three-beam. Some species of poultry had horns, spikes, shells.
The emergence of interest in dinosaurs
In the 30s of the XIX century, the fossilized remains of dinosaurs were first discovered. Then archaeologists did not attach special importance to them and only after some time it became clear that these fossils belong to ancient animals. The very concept of "dinosaur" was introduced by the English zoologist Richard Owen in the middle of the XIX century. From the Latin language, "dinosaur" is translated as "scary", "dangerous", "terrible", and from the ancient Greek language - "lizard", "lizard". Since then, interest in these animals has been constantly growing. How many years ago did dinosaurs die out? The answer to this question is the science of paleontology. Scientists study ancient animals, make films, they become heroes of books. And despite such interest, there is no exact answer to the question of why the dinosaurs became extinct.
Dinosaur era
At the end of the Permian period, the formation of a single continent - Pangea. A characteristic feature of this time was global volcanic activity and the extinction of about 90% of animals. Reptiles adapted best to new conditions. At the beginning of the Triassic, a group of reptiles called "pelicosaurs" appeared. By the middle of the Triassic period they were replaced by a group of reptiles with the name "therapsids". In parallel with the therapsids, a new group of reptiles - archosaurs - developed. This group of reptiles is the ancestor of all dinosaurs, pliosaurs, crocodilomorphs, ichthyosaurs, placodonts and pterosaurs. The next type of reptile was called tecodonts and was adapted to life on land. And already from them dinosaurs got their development. Extinct animals adapted well and took dominant positions on land, in water and in the air.
During the Triassic, the following dinosaur species existed : celophysis, muszavr, and procomsognatus. Plant dinosaurs developed and evolved.
The largest animals lived in the Jurassic period. In the late Jurassic period, land animals began to appear - brachiosaurus, diplodocus, etc.
In the Cretaceous period, predatory reptiles began to prevail in the seas and oceans. New species of dinosaurs appear.
End of an era
The Cretaceous is the heyday of giant dinosaurs, aerial pterodactyls and marine reptiles. At the end of the Cretaceous, the Pangea continent split into Gondwana and Laurasia. The climate on Earth is becoming much colder, ice caps form at the poles. Flowering plants appear , and the number of insects increases.
All this led to the extinction of many species of plants and animals, including dinosaurs. They did not die out overnight, but when you consider that their dominance lasted 160 million years, their disappearance occurred rather quickly. The causes of the disaster that occurred in the Cretaceous are still not clear.
But are all dinosaurs extinct? The descendants of ancient reptiles are crocodiles, lizards and birds that exist today. The first birds appeared in the Cretaceous era, and by the end of the era they already had a developed plumage. When the dinosaurs became extinct, the birds adopted the baton of evolution.
Astrophysical Extinction Hypotheses
The fall of an asteroid is one of the common versions. The time of its fall coincides with the formation of the Chicxulub crater (Mexico, Yucatan Peninsula). These events occurred about 65 million years ago, during the period when the dinosaurs became extinct. Perhaps the fall of the asteroid entailed destructive actions, as a result of which there was a mass extinction of all living things.
The multiple fall hypothesis states that the asteroid fell several times. In addition to the Chiksulub crater, there is a Shiva crater in the Indian Ocean, which formed around the same time. This hypothesis explains why extinction occurred gradually.
There is also a version of a supernova explosion and a comet collision with the Earth.
Geological and climatic hypotheses of extinction
Significant changes took place on the planet during the period when dinosaurs began to disappear. How animals died out, suggests the theory of changes in annual and seasonal temperatures. Large individuals need a warm and even climate. Volcanic activity could lead to a change in the composition of the atmosphere and cause a greenhouse effect. A large outburst of volcanic ash could provoke a volcanic winter, thereby changing the Earth's illumination. A significant decrease in sea level, cooling of the ocean, changes in the composition of sea water and a sharp jump in the Earth's magnetic field could also contribute to the extinction of dinosaurs.
Evolutionary biological extinction hypotheses
One of the hypotheses of this group adheres to the situation of a mass epidemic. It is possible that dinosaurs could not adapt to the changing vegetation, which led to poisoning. The probability of killing eggs and cubs by the first predatory mammals is high. There is also a version that during the ice age, females disappeared. Scientists have proposed another version of the death of dinosaurs - asphyxiation: in the atmosphere there was a sharp decrease in the amount of oxygen.
Why did the dinosaurs disappear?
Why did the dinosaurs disappear? How did these ancient animals die out ? Various theories and hypotheses provide answers to these questions, but not one of them answers all the questions in full. It is known that extinction of species began long before the time of the catastrophe, and the astronomical hypothesis in this case is doubtful. Many theories lack evidence, such as the hypothesis of a regression of the oceans or changes in the magnetic field. Also, the lack of completeness of paleontological data can give a distorted picture.
The combination of hypotheses forms a more visual picture. The hypotheses, complementing each other, give answers to a larger number of questions, and the picture of that time looks more traced and detailed.
The process of evolution - the extinction of the old and the formation of the new - is consistent. And the process of evolution of dinosaurs until the end of the Cretaceous took place naturally. But for some reason, at the end of the Cretaceous, the old species became extinct, but the new ones did not appear, and as a result, this species was completely extinct.
From the point of view of paleontology
The great extinction version is based on the following facts:
- The appearance of flowering plants.
- Gradual climate change caused by continental drift.
According to the scientific world, the following picture was observed. The developed root system of flowering plants and their better adaptability to soils quickly replaced other types of vegetation. Insects began to appear, which fed on flowering plants, and previously appeared insects began to disappear.
The root system of flowering began to grow and impede the process of soil erosion. The land surface ceased to erode, and nutrient material ceased to flow into the oceans. This led to the depletion of the ocean and the death of algae, which, in turn, are producers of biomass in the ocean. Ecosystem disruption occurred in water, which caused mass extinction. It is believed that flying dinosaurs are closely connected with the sea, so the extinction chain has also spread to them. On land, they tried to adapt to the green mass. Small mammals and small predators began to appear. This was a threat to the offspring of dinosaurs, as the eggs and cubs of the dinosaurs became food for the predators that appeared. As a result, conditions were created that are negative for the emergence of new species.
When the dinosaurs became extinct, the era of the Mesozoic ended, and with it the active tectonic, climatic and evolutionary activities ended.
Children and dinosaurs
Interest in ancient animals is not only in adults, but also in children. Today the project “Why did dinosaurs die out?” included in the program of kindergartens and primary classes. The uniqueness of such an activity lies in the fact that the child independently develops cognitive abilities, seeks answers to questions and receives new knowledge. The question of why dinosaurs became extinct is as curious for children as it is for scientists. The interest is primarily caused by the fact that these animals do not exist on earth today and an exact answer to the question about the reasons for their extinction has not yet been received.