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Dinosaurs are a species that appeared in the Upper Triassic, about 230 million years ago, most likely in South America. Dinosaurs were the dominant animals during the Mesozoic Era, between 250 million and 65 million years ago.
The word dinosaur means "monstrous lizard" and was coined after the recognition that dinosaurs were reptiles. However, it was later discovered that dinosaurs are neither lizards nor reptiles, but constitute a separate group of animals.
Belonging to the sauropsid diapsid group, dinosaurs comprise about 9,000 species. Dinosaurs vary greatly in weight and size, with the smallest being chin-lengths of a meter and the largest about 50 meters long.
In addition, some dinosaurs are bipedal, while others are quadrupedal or semi-bipedal. The diet of these animals also changes according to species: while some are carnivores, others are herbivores. Until the first half of the twentieth century, dinosaurs were thought to be slow, unintelligent and cold-blooded. The scientific community has, however, since discovered that dinosaurs were active animals with a high metabolism and numerous adaptations for social interaction.
Dinosaurs became extinct at the end of the Mesozoic Era, but how is still unclear today. Some scientists believe these animals disappeared from Earth due to the fall of the asteroid Chicxulub, whose impact on Earth would have raised a blanket of dust surrounding Earth and made the planet unlivable for a long time.
Other scientists, however, attribute the cause of the event from intense volcanic activity in the Deccan region in western India, an event that could have had the same consequences on Earth as the asteroid fall.