The specimen shown here may be quite tiny, but Diplodocus was one of the large dinosaurs: it could be up to 27 m long (with the tail accounting for half of this length)! In common with other sauropods, its neck and vertebrae had large cavities – pleurocoels – that made them lighter but not less strong.
Sauropods such as the Diplodocus were built like a suspension bridge. The pillars were the front legs (with shoulders) and the hind legs (with hips). The cables were the thick ligaments running along the top of the spinal column. The ligaments were tightened by the long neck and tail, which helped to carry the weight of the chest.
The last few metres of the Diplodocus' extremely long tail were amazingly flexible. This tail-end may have reached supersonic speeds, cracking like a whip. It was too brittle to injure predators but the cracking sound may have been enough to keep them at a distance. Within the herd it may also have been used as a sign of recognition or alarm signal.