Dinosaurs first appeared during the Triassic period, between 243 and 233.23 million years ago, although the exact origin and timing of the evolution of dinosaurs is the subject of active research. 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. This book briefs its readers on the history, evolution, classification and biology of Dinosaurs. This book is a compilation of high quality articles from the Internet.