Dinosaurs are the collective name for a group of reptiles that appeared during the Mesozoic (Triassic, Jurassic, and Cretaceous). The healthy limbs, long tail, and large body are the portrayal of most dinosaurs. They mainly inhabit forests or open areas on lakeside plains (or coastal plains). In 1841, British scientist Richard Owen studied several pieces like lizard bone fossils and thought they were some kind of prehistoric animals, and named dinosaurs, meaning "horrible lizards." The dinosaurs suddenly disappeared at the end of the Cretaceous Period 65 million years ago, becoming a mystery in the evolutionary history of the Earth's biology. This mystery is still unsolvable. The past creatures of the earth are recorded in fossils. Many fossils of dinosaurs have been found in the Mesozoic strata. There are a large number of bones that can be seen or presented in a variety of shapes. However, in the next Cenozoic strata, the fossils of non-bird dinosaurs were completely invisible, and it was inferred that non-bird dinosaurs were extinct together during the Mesozoic era. Today, only birds are preserved, and most scientists recognize that “birds belong to The term "dinosaur".