Dinosaurs are ancient creatures that appeared on the planet approximately 225 million years ago. For 160 million years, these animals dominated the planet. The extinction period took about 5 million years, and for about 65 million years they have been absent in the animal world. There are many hypotheses as to why the dinosaurs disappeared. How these animals died out and ceased to exist, we will tell in our article.
Dinosaurs Appear
Planet Earth was inhabited by different types 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 protozoan plants were seaweeds, and the first animals were small sea molluscs. The appearance of fish occurred about 500 million years ago. Approximately 370 million years ago, the first animals came to land - amphibians. Reptiles are a new group of animals that appeared about 300 million years ago. The animals had scaly skin, could lay eggs, and be permanently on land. next in the chainevolution became dinosaurs. An extinct species of animal gave impetus to the development of such a science as paleontology.
Description of dinosaurs
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 fossilized remains. Fossils suggest that they were reptiles, like crocodiles, lizards, turtles and snakes. Dinosaurs range in size from tiny to giants. They had four limbs and a tail. Dinosaurs stood and moved on straight limbs, some on their hind legs, others on all four, and still 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 died out.
Dinosaurs are divided into two groups: lizards and ornithischians. The difference between the groups is in the structure of the pelvic bones. In lizard dinosaurs, the structure of the pelvis is four-rayed, and in ornithischians it is three-rayed. Some species of ornithischians had horns, spikes, shells.
The emergence of interest in dinosaurs
In the 30s of the 19th century, the fossilized remains of dinosaurs were first discovered. Then archaeologists did not attach much 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 19th century. WithLatin language "dinosaur" is translated as "terrible", "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 become extinct? The answer to this question is given by the science of paleontology. Ancient animals are studied by scientists, filmed in films, they become heroes of books. And despite such interest, there is no exact answer to the question of why dinosaurs died out.
Dinosaur Age
At the end of the Permian period, a single continent, Pangea, was formed. A characteristic feature of this time was global volcanic activity and the disappearance of about 90% of animals. Reptiles have adapted best to the 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 called "therapsids". In parallel with the therapsids, a new group of reptiles, the archosaurs, developed. This group of reptiles is the ancestor of all dinosaurs, pliosaurs, crocodylomorphs, ichthyosaurs, placodonts, and pterosaurs. The next type of reptile was called thecodonts and was adapted to life on land. And dinosaurs have already developed from them. Extinct animals have adapted well and have taken dominant positions on land, in water and in the air.
During the Triassic period, the following types of dinosaurs existed: Coelophysis, Mussaurus and Procompsognathus. Plant dinosaurs developed and evolved.
The largest animals lived in the Jurassic period. In the Late Jurassicland animals began to appear - brachiosaurus, diplodocus, etc.
In the Cretaceous period, predatory reptiles began to predominate in the seas and oceans. New types of dinosaurs appear.
The end of an era
The Cretaceous period is the heyday of giant lizards, air pterodactels and marine reptiles. At the end of the Cretaceous, the Pangea continent split into Gondwana and Laurasia. The climate on Earth becomes much colder, ice caps form at the poles. Flowering plants appear and insects increase.
All this led to the extinction of many species of plants and animals, including dinosaurs. They did not die out overnight, but given that their dominance lasted 160 million years, their disappearance happened quite quickly. The causes of the catastrophe that occurred during the Cretaceous period are still not clear.
But are all dinosaurs extinct? The descendants of ancient reptiles are the crocodiles, lizards and birds that exist today. The first birds appeared in the Cretaceous, and by the end of the era they already had developed plumage. When dinosaurs became extinct, birds took over the baton of evolution.
Astrophysical extinction hypotheses
The fall of an asteroid is one of the most common versions. The time of its fall coincides with the formation of the Chicxulub crater (Mexico, Yucatan Peninsula). These events took place approximately 65 million years ago, during the period when the dinosaurs became extinct. Perhaps the fall of the asteroid led to destructive actions, as a result of which there was a mass extinctionall living things.
The multiple fall hypothesis states that the asteroid fell several times. In addition to the Chicxulub crater, there is the Shiva crater in the Indian Ocean, which formed around the same time. This hypothesis explains why the extinction occurred gradually.
There is also a version of a supernova explosion and a comet colliding with the Earth.
Geological and climatic extinction hypotheses
The planet was undergoing significant changes during the period when the dinosaurs began to disappear. How animals died out is suggested by the theory of changes in average 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 emission of volcanic ash could provoke a volcanic winter, thereby changing the illumination of the Earth. A significant drop in sea level, cooling of the ocean, a change in the composition of sea water and a sharp jump in the Earth's magnetic field may also have contributed to the extinction of the dinosaurs.
Evolutionary biological hypotheses of extinction
One of the hypotheses of this group adheres to the situation of the emergence of a mass epidemic. It is possible that dinosaurs could not adapt to the changed vegetation, which led to poisoning. The probability of destruction of eggs and cubs by the first predatory mammals is high. There is also a version that females disappeared during the Ice Age. Scientists have proposed another version of the death of dinosaurs - suffocation: inatmosphere, there was a sharp decrease in the amount of oxygen.
Why did dinosaurs disappear?
Why did the dinosaurs disappear? How did these ancient animals become extinct? A variety of theories and hypotheses provide answers to these questions, but none of them fully answers all questions. It is known that the extinction of species began long before the moment of the catastrophe, and the astronomical hypothesis in this case is doubtful. Many theories lack factual data, such as the hypothesis of the regression of the World Ocean or changes in the magnetic field. Also, the lack of completeness of paleontological data can give a distorted picture.
Combining hypotheses creates a clearer picture. Hypotheses, complementing each other, provide answers to more 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 period occurred naturally. But for some reason, at the end of the Cretaceous period, the old species died out, and the new ones did not appear, and, as a result, there was a complete extinction of this species.
From a paleontological point of view
The great extinction version is based on the following facts:
- The emergence 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, their better adaptability to soils quickly replaced otherstypes of vegetation. Insects that fed on flowering plants began to appear, and insects that had previously appeared began to disappear.
The root system of flowering plants began to grow and prevent the process of soil erosion. The surface of the land ceased to erode, and nutrient material ceased to flow into the oceans. This led to the impoverishment of the ocean and the death of algae, which, in turn, are producers of biomass in the ocean. In the water there was a violation of the ecosystem, which caused a mass extinction. It is believed that flying lizards are closely related to the sea, so the chain of extinction 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, since the eggs and cubs of dinosaurs became food for the appeared predators. As a result, conditions were created that are negative for the emergence of new species.
When the dinosaurs died out, the Mesozoic era ended, and active tectonic, climatic and evolutionary activity also ended with it.
Children and dinosaurs
Interest in ancient animals is not only among adults, but also among children. Today the project "Why did the dinosaurs become extinct?" included in the kindergarten and elementary school curriculum. The uniqueness of such activities lies in the fact that the child independently develops cognitive abilities, seeks answers to questions and gains new knowledge. The question of why dinosaurs became extinct is as curious for children as it is for scientists. Interest is primarily due to the fact that these animals are not on earth today and the exact answer to the question of the reasons for their disappearance has not yet been received.
