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 Archosauria. Archosaurs are a group of amphibians that first appeared in the late Permian period and rose to prominence in the mid-Triassic period.
Until the early 20th century, scientists and the public believed that dinosaurs were slow, cold-blooded creatures with no developed brains. However, survey results since the 1970s have shown that they are active creatures with a very high metabolism and adaptability for social interaction. Thus, the differences in attitudes that were formed in the early stages were the reason for the evidence that theropod dinosaurs gave rise to birds.
Ever since the first fossils of dinosaurs were identified in the early 19th century, models of these dinosaurs, which are widely housed in museums around the world, have attracted more and more audiences. Dinosaurs became part of the world's culture and continue to be popular with children and adults. These creatures provided the titles for best-selling books and movies (Jurassic Park) and new discoveries about them continue to be covered by the media.
The term dinosaur is sometimes used informally to refer to other prehistoric reptiles such as Pelycosaur dimetrdon, feathered pterosaurs, aquatic ichthyosaurs, plesiosaurs and mosasaurs. However, none of these groups were dinosaurs.
In English colloquialism, the term "dinosaur" is sometimes used to describe an obsolete or failed person or thing. The reason for using this term was because dinosaurs were known as slow and cold-blooded creatures.