Knowledge about dinosaurs comes from both fossil and nonfossil records, including fossilized bones, feces, trackways, gastroliths, feathers, impressions of skin, internal organs and "soft tissues”. Dinosaurs are animals that dominated the terrestrial ecosystem for over 100 million years.The term is also used informally to describe any prehistoric reptile, such as the pelycosaur Dimetrodon, the winged pterosaurs, and the aquatic ichthyosaurs, plesiosaurs, and mosasaurs, though none of these are dinosaurs.

Since the first dinosaur was recognized in the 19th century, their mounted skeletons have become major attractions at museums around the world. Dinosaurs have become a part of world culture and remain consistently popular, especially among children. They have been featured in best-selling books and blockbuster films such as Jurassic Park, and new discoveries are regularly covered by the media. Non-avian dinosaurs became extinct at the end of the Cretaceous period, 65 million years ago.

The on-going dinosaur renaissance began in the 1970s and was triggered, in part, by John Ostrom's discovery of Deinonychus-- an active, vicious predator that may have been warm-blooded (homeothermic), in marked contrast to the prevailing image of dinosaurs as sluggish cold-blooded reptiles. Vertebrate paleontology has also become a global science, with major new discoveries in previously unexploited regions, including South America, Madagascar, Antarctica, and most significantly the amazingly well-preserved feathered dinosaurs in China, which have further solidified the link between dinosaurs and their living descendants, the 9,000+ species of modern birds. The widespread application of cladistics, which rigorously analyzes the relationships between biological organisms, has also proved tremendously useful in classifying dinosaurs, which are still known from an incomplete fossil record.