Paleontologist John Ostrom's study of "Deinonychus" in the late 1960s started the debate on whether dinosaurs were warm-blooded. It is now accepted that all or most smaller theropods had feathers whose function was temperature regulation. Ostrom noted the small body, sleek, horizontal, posture, and the enlarged claws on the feet, which suggested the animal was an active, agile predator. Before this, the popular idea of dinosaurs had been one of plodding, reptilian giants.