Dinosaurs are a diverse
group of animals of the clade Dinosauria that first appeared during the Triassic period. Although the exact origin and timing of the
evolution of dinosaurs is the subject of active research,[1]the current scientific
consensus places their origin between 231 and 243 million years ago.[2] They became the
dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201 million years
ago. Their dominance continued through the Jurassic and Cretaceous periods and ended when the Cretaceous-Paleogene extinction event led to the
extinction of most dinosaur groups 66 million years ago.
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