恐龙是已经灭绝的史前爬行动物,它们生活在地球历史的中生代。中生代分三个纪:三叠纪、侏罗纪和白垩纪,从2.3亿年前起。至6700万年前止。恐龙大约出现在三叠纪的中晚期,侏罗纪和白垩纪时很繁盛;但到白垩纪末,恐龙突然在世界各地全部消失。恐龙是中生代的主角,它的一些爬行亲戚也先后扮演了比较重要的角色。因此,中生代常被人们称为“恐龙时代”或“爬行动 Dinosaurs are extinct prehistoric reptiles that live in the Mesozoic of Earth's history. The Mesozoic is divided into three disciplines: Triassic, Jurassic and Cretaceous, from 230 million years ago. Until 67 million years ago. The dinosaurs appeared in the middle and late Triassic, and thrived in the Jurassic and Cretaceous. But by the end of the Cretaceous dinosaurs suddenly disappeared all over the world. Dinosaurs are the protagonists of the Mesozoic, and some of its crawling relatives have also played a more important role. Therefore, the Mesozoic are often referred to as “dinosaur age” or “crawling.”