Dinosaurs: An overview
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65 million years ago the last dinosaurs died out. They were part of a group of reptiles that dominated the planet for 140 million years. How did their evolution come about? Why did they disappear?
Dinosaurs are known mainly through the study of fossils. After long and careful research, paleontologists (scientists who study the extinct species) reached a fairly accurate knowledge of the dinosaurs. There is now much information about their origins, their anatomy, habitat, lifestyle and reproduction, as well as the different species and their geographical distribution.
The rise and decline of animal species can be explained by the theory of evolution set out in the nineteenth century by an English scientist, Charles Darwin. He showed how the most strongest animals or rather best suited to their environment survive and reproduce more readily than others.
After several generations, the animals less adapted disappear: this is called "natural selection". The first form of life appeared on Earth around 3500 million years ago. The earliest forms of life are probably bacteria, whose fossils were found in South Africa in a stone called "flint". Then came the plants. The first animals lived in water, as evidenced by the green trilobite fossils, flat creatures whose body was divided into three parts and crawled at the bottom of the sea
The first fish appeared about 400 million years ago. Some of them have managed to live on land by establishing strong lungs and fins. In a few million years, they adapted to terrestrial life, even if they returned to the water to lay their eggs. These animals can live both in water and on land and were a class of amphibians. In about 280 million years the Earth's climate became warm and dry which dried up wetlands and the consequence was that most amphibians disappeared. With this development, the first class of reptiles began evolve. They have a thick scaly skin and can lay their eggs on land.
Geologists (scientists who study rocks composing the crust) have divided the history of the Earth into periods of millions of years. The onset of the Permian reptiles date (the first fossils of reptiles were discovered in Perm, Russia), between 286 and 248 million BC.
The birth of dinosaurs - At the end of the Permian (about 260 million years ago), reptiles spread a little. During the following period, the Triassic (248 to 213 million years BC), multiple dinosaur species emerged, including cynodontes herbivores and cynognathes carnivores. The cynognates were gradually replaced by archosaurs: the name simply means "reptile domination."
The Brachiosaurus ate only plants. They probably ate nearly a ton of leaves per day to survive.
In some fossils of sauropods, they found large stones in the skeleton at the site of the stomach. Scientists believe that dinosaurs swallowed stones or pebbles to help the stomach grind twigs and leaves. Some herbivorous dinosaurs like the Stegosaurus, were protected by bony plates forming a dorsal crest and sword like tips on the tail.
Tags: Stegosaurus, sauropods, Brachiosaurus , dinosaurs