Deinonychus
Deinonychus is a genus of carnivorous dromaeosaurid ceolurosaurian dinosaurs. There is one described species,
Deinonychus antirrhopus. This species, which could grow up to 3.4 metres long, lived during the early Cretaceous Period, about 115–108 million years ago. Fossils have been recovered from the U.S. states of Montana, Wyoming, and Oklahoma, in rocks of the Cloverly Formation and Antlers Formation, though teeth that may belong to
Deinonychus have been found much farther east in Maryland. Paleontologist John Ostrom's study of
Deinonychus in the late 1960s revolutionized the way scientists thought about dinosaurs, leading to the "dinosaur renaissance" and igniting the debate on whether dinosaurs were warm-blooded or cold blooded. Before this, the popular conception of dinosaurs had been one of plodding, reptilian giants. Ostrom noted the small body, sleek, horizontal posture, ratite-like spine, and especially the enlarged raptorial claws on the feet, which suggested an active, agile predator. "Terrible claw" refers to the unusually large, sickle-shaped talon on the second toe of each hind foot.