Paleontologist John Ostrom's study of "Deinonychus" in the late 1960s changed the way scientists thought about dinosaurs. It caused the "dinosaur renaissance" and made scientists argue whether dinosaurs were warm-blooded or cold-blooded. Before this, most people thought dinosaurs were big, slow, and looked and acted like modern reptiles. Ostrom told other scientists that "Dienocus" had a small body, sleek, horizontal posture, the same kind of spine that flightless birds have, and the large claws on its feet. All this, said Ostrom, meant "Deinonychus" was probably very fast and caught its food like a predator.