Birth of the "terrible lizards"
In 1824 William Buckland described a huge fossil jaw as Megalosaurus, and the following year Gideon Mantell reported the plant-eater Iguanodon. In 1842 the anatomist Richard Owen grouped such animals as Dinosauria, Greek for "terrible lizards". In the late 19th century Othniel Marsh and Edward Cope raced each other across the American West in the "Bone Wars", naming Triceratops, Stegosaurus and many more. For decades dinosaurs were seen as slow, sluggish cold-blooded animals — evolutionary failures.
The dinosaur renaissance and feathers
In 1969 John Ostrom described the agile predator Deinonychus and argued that dinosaurs were active and strikingly bird-like; his student Robert Bakker popularised warm-blooded dinosaurs in his 1975 article "Dinosaur renaissance". In 1996 Sinosauropteryx, with filament-like structures, was found in the Yixian Formation of Liaoning, China, and in 2003 Xu Xing and colleagues reported the four-winged Microraptor. Most researchers now agree that birds evolved from theropod dinosaurs. In 2005 Mary Schweitzer reported soft-tissue-like structures in Tyrannosaurus bone, a finding whose nature is still debated, and in 2017 a new hypothesis proposing to reshuffle the main dinosaur groups sparked debate. South Korea's Goseong, Haenam and Hwasun have yielded footprint fossils on a world-class scale.
The extinction puzzle
About 66 million years ago, at the end of the Cretaceous, all dinosaurs except birds vanished. In 1980 the Alvarez team proposed an asteroid impact based on an iridium anomaly, and confirmation of the Chicxulub crater in the 1990s made this the leading explanation: dust and soot blocked sunlight and food chains collapsed. Some researchers argue that massive Deccan volcanism in India also played a role. After this mass extinction, mammals filled the empty niches and shaped today's ecosystems. Despite the films, Tyrannosaurus never lived alongside humans, and pterosaurs and plesiosaurs, though close relatives, were not technically dinosaurs.
FAQ
- Were pterosaurs and plesiosaurs dinosaurs?
- No. Pterosaurs were flying reptiles and plesiosaurs marine reptiles; they lived at the same time but are not classified as dinosaurs.
- Are birds really dinosaurs?
- Yes. Feathered fossils and skeletal analyses show that birds branched from theropod dinosaurs, so phylogenetically birds are living dinosaurs.
Sources reviewed: 2026-10-26
References
- Buckland, W. (1824). Notice on the Megalosaurus or great fossil lizard of Stonesfield. Transactions of the Geological Society of London, 2nd series, 1, 390–396.
- Mantell, G. A. (1825). Notice on the Iguanodon, a newly discovered fossil reptile, from the sandstone of Tilgate forest, in Sussex. Philosophical Transactions of the Royal Society of London, 115, 179–186.
- Owen, R. (1842). Report on British fossil reptiles. Part II. Report of the British Association for the Advancement of Science, 11, 60–204.
- Ostrom, J. H. (1969). Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana. Bulletin of the Peabody Museum of Natural History, 30, 1–165.
- Bakker, R. T. (1975). Dinosaur renaissance. Scientific American, 232(4), 58–78.
- Alvarez, L. W., Alvarez, W., Asaro, F., & Michel, H. V. (1980). Extraterrestrial cause for the Cretaceous–Tertiary extinction. Science, 208(4448), 1095–1108.
- Chen, P.-J., Dong, Z.-M., & Zhen, S.-N. (1998). An exceptionally well-preserved theropod dinosaur from the Yixian Formation of China. Nature, 391(6663), 147–152.
- Xu, X., et al. (2003). Four-winged dinosaurs from China. Nature, 421(6921), 335–340.
- Schweitzer, M. H., Wittmeyer, J. L., Horner, J. R., & Toporski, J. K. (2005). Soft-tissue vessels and cellular preservation in Tyrannosaurus rex. Science, 307(5717), 1952–1955.
- Baron, M. G., Norman, D. B., & Barrett, P. M. (2017). A new hypothesis of dinosaur relationships and early dinosaur evolution. Nature, 543(7646), 501–506.