Many millions years ago flora and fauna of Earth strongly differed from modern. In particular, on Earth, dinosaurs - beings whose existence is connected with numerous conjectures and even legends lived.
Appearance of dinosaurs
Dinosaurs are nadotryad an extensive class of reptiles. The climate changes which happened on Earth 300 million years ago became the beginning of history of dinosaurs. There was a substantial increase of average temperature that promoted extinction of some types and distribution of others. In particular, blossoming of reptiles began.
Both the quantity of individuals, and quantity of types increased. From them there were also ancestors of dinosaurs - archosaurs. Modern representatives of this group of reptiles are crocodiles. Archosaurs of the Permian Period differed in specifics of the structure of teeth and also a specific protective coating of skin - scales. As well as modern crocodiles, they laid eggs.
Carnivorous dinosaurs ate generally small mammals. Also there were herbivorous dinosaurs with a vegetable diet.
After Mass Perm extinctions remained of only 5% of the types existing earlier, and ancestors of dinosaurs managed to endure this ecological revolution. Dinosaurs arose 230 million years ago. The earliest species of dinosaurs known for the scientist is stavrikozavr. It was about 2 m long, and its weight reached 30 kg. Stavrikozavr was a predator and moved on hinder legs.
Era of dinosaurs and their decline
Gradually dinosaurs became more and more various group of beings, taking all new areas of dwelling. Dinosaurs could live also in water, competing with large predatory fishes. Gradually there were flying dinosaurs. Also over time the sizes of reptiles became more and more various - their weight could reach 200 kg and more. Blossoming of dinosaurs fell on the cretaceous and Jurassic periods when species of dinosaurs made more than a half of all types of fauna of Earth. In total remains about 500 species of dinosaurs were found, but scientists consider what them was much more - till 2000 for all the time of existence of this nadotryad.
The largest dinosaurs were herbivorous or lived in water.
The exact reason of disappearance of dinosaurs remains to the unknown. One of theories assumes that dinosaurs died because of falling of a meteorite and the tsunami caused by it and other cataclysms. Other scientists consider that gradual change of climate which led to extinction not only dinosaurs was the cause, but also some other types - disappeared up to 20% of species of flora and fauna. Only the fact that dinosaurs disappeared at the end of the Cretaceous - about 65 million years ago is precisely known. Domination of reptiles was succeeded by wide circulation of mammals.