Paleontologists had long supposed that the dinosaur Diplodocus browsed for high-growing vegetation such as treetop leaves by raising its very long neck  But now computer models have shown that the structure of Diplodocuss neck bones would have prevented such movement  The neck could, however, bend downward and even extend below ground level, allowing Diplodocus to access underwater vegetation from dry land
Thus, Diplodocus must have fed on plants on or near the ground, or underwater
Diplodocus had no other way of accessing high-growing vegetation, such as by rising up on its hind legs.