DINOSAURS were the dominant vertebrate animals of terrestrial ecosystems for over 160 million years, from the late Triassic Period (about 230 million years ago) until the end of the Cretaceous Period (65 million years ago), when most of them became extinct in the Cretaceous–Tertiary extinction event. The 10,000 living species of birds have been classified as dinosaurs.

The dinosaur pictures are organised into groups and each group has its own tabbed page.

Clockwise from top-left: Minmi, Hypacrosaurus, Suchomimus, Pelorosaurus and center, Albertaceratops

Dinosaurs were an extremely varied group of animals; according to a 2006 study, over 500 dinosaur genera have been identified with certainty so far, and the total number of genera preserved in the fossil record has been estimated at around 1,850, nearly 75% of which remain to be discovered. An earlier study predicted that about 3,400 dinosaur genera existed, including many which would not have been preserved in the fossil record. As of September 17, 2008, 1,047 different species of dinosaurs have been named. Some were herbivorous, others carnivorous. Some dinosaurs were bipeds, some were quadrupeds, and others, such as Ammosaurus and Iguanodon, could walk just as easily on two or four legs. Many had bony armor, or cranial modifications like horns and crests. Although known for large size, many dinosaurs were human-sized or smaller. Dinosaur remains have been found on every continent on Earth, including Antarctica. No dinosaurs are known to have lived in marine or aerial habitats, although it is possible some feathered theropods were flyers.