John Ostrom

John Harold Ostrom (February 18, 1928 – July 16, 2005) was an American paleontologist who revolutionized the modern understanding of dinosaurs. Ostrom's work inspired what his pupil Robert T. Bakker has termed a "dinosaur renaissance".

Beginning with the discovery of Deinonychus in 1964, Ostrom challenged the widespread belief that dinosaurs were slow-moving lizards (or "saurians"). He argued that Deinonychus, a small two-legged carnivore, would have been fast-moving and warm-blooded.

Further, Ostrom's work made zoologists question whether birds should be considered an order of Reptilia instead of their own class, Aves. The idea that dinosaurs were similar to birds was first proposed by Thomas Henry Huxley in the 1860s, but was dismissed by Gerhard Heilmann in his influential book The Origin of Birds (1926). Prior to Ostrom's work, the development of birds was generally believed to have split off early on from that of dinosaurs.

Ostrom showed more bird-like traits common in dinosaurs and proved that birds themselves are in fact a group of coelurosaurian theropods, a descendant of dinosaurs. The first of Ostrom's broad-based reviews of the osteology and phylogeny of the primitive bird Archaeopteryx appeared in 1976. Ostrom lived to see the eventual discovery of feathered dinosaurs in northeastern China, confirming his theories about dinosaurs being progenitors of birds, and the existence of dinosaurs with feathered plumage.