 Finds of sauropod footprints in the 1930s eventually put Hay's theory to rest.Later, diplodocids were often portrayed with their necks held high up in the air, allowing them to graze from tall trees.Studies looking at the morphology of sauropod necks have concluded that the neutral posture of "Diplodocus" neck was close to horizontal, rather than vertical, and scientists such as Kent Stevens have used this to argue that sauropods including "Diplodocus" did not raise their heads much above shoulder level.