Fossil range: 230–65 Ma
Descendant taxon Aves survives to present.
Mounted skeletons of Tyrannosaurus (left) and Apatosaurus (right) at the
American Museum of Natural History.
Orders and suborders
• Cerapoda †
• Thyreophora †
• Sauropodomorpha †
Dinosaurs (Greek δεινόσαυρος, deinosauros) 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 extinc-
tion event. The 10 000 living species of birds have been
classified as dinosaurs.
The term "dinosaur" was coined in 1842 by Sir
Richard Owen and derives from Greek δεινός (deinos)
"terrible, powerful, wondrous" + σαῦρος (sauros) "lizard".
It is sometimes used informally to describe other prehis-
toric reptiles, such as the pelycosaur Dimetrodon, the
winged pterosaurs, and the aquatic ichthyosaurs, plesio-
saurs and mosasaurs, although none of these animals
were dinosaurs. Through the first half of the 20th cen-
tury, most of the scientific community believed dino-
saurs to have been slow, unintelligent cold-blooded an-
imals. Most research conducted since the 1970s,
however, has supported the view that dinosaurs were
active animals with elevated metabolisms and numerous
adaptations for social interaction. The resulting trans-
formation in the scientific understanding of dinosaurs
has gradually filtered into popular consciousness.
The 1861 discovery of the primitive bird Archaeo-
pteryx first suggested a close relationship between dino-
saurs and birds. Aside from the presence of fossilized
feather impressions, Archaeopteryx was very similar to
the contemporary small predatory dinosaur Compso-
gnathus. Research h