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Dinosaurs were the dominant terrestrial vertebrate animals for over 160 million years, from the late Triassic period (about 230 million years ago) until the end of the Cretaceous period (about 65 million years ago), when the Cretaceous–Tertiary extinction event caused the extinction of most dinosaur species. The fossil record indicates that birds evolved from theropod dinosaurs during the Jurassic period, and most paleontologists regard them as the only clade of dinosaurs to have survived until the present day.[1]

Dinosaurs were a varied group of animals. Paleontologists have identified over 500 distinct genera[2] and more than 1,000 different species of dinosaur,[3] and remains have been found on every continent on Earth.[4] Some dinosaurs were herbivorous, others carnivorous. Some were bipedal, others quadrupedal, and others were able to shift between these body postures. Many species developed elaborate skeletal modifications such as bony armor, horns or crests. Although generally known for their large size, many dinosaurs were human-sized or even smaller. Most major groups of dinosaurs are known to have built nests and laid eggs, suggesting an oviparity similar to that of modern birds.

The term "dinosaur" was coined in 1842 by Sir Richard Owen and derives from Greek δεινός (deinos) "terrible, powerful, wondrous" + σαῦρος (sauros) "lizard". Through the first half of the twentieth century, most of the scientific community believed dinosaurs to have been sluggish, unintelligent cold-blooded animals. Most research conducted since the 1970s, however, has indicated that dinosaurs were active animals with elevated metabolisms and numerous adaptations for social interaction.

Since the first dinosaur fossils were recognized in the early nineteenth century, mounted dinosaur skeletons have been major attractions at museums around the world, and dinosaurs have become a part of world culture. They have been featured in best-selling books and films such as Jurassic Park, and new discoveries are regularly covered by the media. As a result, the word "dinosaur" has entered the vernacular, although its use and meaning in colloquial speech may be inconsistent with modern science. In English, for example, "dinosaur" is commonly used to describe anything that is impractically large, slow-moving, obsolete, or bound for extinction.[5]