Dinosaurs were the most dominant group of vertebrates that lived in terrestrial ecosystems for about 160 million years, from the late Triassic period (about 230 million years ago) to the late Cretaceous period (about 65 million years ago). Most of them became extinct during the Cretaceous-Tertiary extinction stages. With the discovery of Archeopteryx in 1862, the relationship between dinosaurs and birds was first discovered. The fossilized feathers of Archeopteryx clearly distinguished it from its contemporaries, the small predatory dinosaurs Compsognathus. Surveys since the 1970s have found that theropod dinosaurs are the closest ancestors of birds. However, according to the majority of paleontologists, birds are the only living dinosaurs, and some believe that dinosaurs and birds should be classified under the same species. Crocodiles are another living species closely related to the dinosaurs, both of which are members of the order Archosauri...