The first fossils of Deinonychus were discovered in 1931 by a team led by Barnum Brown, who at the time was more concerned with digging up the remains of another dinosaur, Tenontosaurus.
About 30 years later, paleontologist John Ostrom found much more Deinonychus material, allowing him to describe the dinosaur in more detail. His description shook the world of paleontology and changed a lot about how many people viewed dinosaurs. He believed that Deinonychus was a quick and agile predator, not the lumbering, slow-moving dinosaurs that was the common public perception at the time.
This led to even more ideas, such as the suggestion that dinosaurs were warm-blooded, and may have more in common with modern day birds than reptiles. This “Dinosaur Renaissance” would reshape how many people pictured dinosaurs, and we now know not only that dinosaurs were warm-blooded, but that many had feathers and very likely evolved into birds.