Zoologists believe that today's chelonians have evolved from a kind of dinosaur that lived during the Carboniferous Period. They and other reptiles such as lizards, chameleons, snakes, and alligators were among the first animals to adapt to life on dry land. Through them, life has made the transition from fish to mammal.
在二億年前恐龍主宰地球時代，它們與蜥蜴、變色龍、蛇類、鱷魚等爬蟲類已經存在，也是第一個適應陸地上乾燥生活的動物，在魚類與鳥類、哺乳動物間扮演過渡性角色。