The Triassic Period was the first period of the Mesozoic Era, which lasted from about 252 million to 201 million years ago. During this time, the first dinosaurs appeared and diversified into many different species. This period also saw the emergence of other reptiles, such as pterosaurs and crocodiles, as well as the first mammals. The Triassic Period was marked by a warm climate and the breakup of the supercontinent Pangaea.