The familiar long, low sauropod is known as Diplodocus. It is well-known from the many casts of the graceful skeleton of D. carnegii, the second species to be found. The casts, which appear in museums throughout the world, were excavated, reproduced and donated with finance provided by the Scottish-American steel magnate Andrew Carnegie in the early years of the 20th century.
Name: Diplodocus, meaning ‘double beam’
Size: 27m (up to 40m in the case of D. hallorum) long and 3.6m high
Food: plants and leaves from trees
Lived: 150-138 million years ago in the Late Jurassic Period in North America
When humans walk, the movement of the ankles make the body move up and down. For sauropods like Diplodocus, any movement of their heavy bodies used up a lot of energy. Fossilised footprints show that sauropods had broad, round feet like an elephant’s, with short stubby toes.
A sort of wedge may have raised Diplodocus’ toes from the ground, just like the heel of a shoe. This meant that muscles did not have to work so hard to support the dinosaur’s body as it walked.
From its tiny head to the tip of its enormous tail, Diplodocus had a long line of bones called vertebrae. Its neck had 15, its back 10, and its tail about 70.
The neck and tail are finely balanced and as a result, Diplodocus could probably have raised itself on to its hind legs to reach high into the trees. The wear on the teeth shows that it could browse high in the treetops or among the undergrowth. Finds in the 1990s have led American palaeontologist Steven Czerkas to suggest that there may have been a row of horny spines down the neck, back and tail.
Diplodocus was built rather like a suspension bridge, with its front and back legs acting like twin towers. On an actual bridge, cables support the road that runs between the towers. Diplodocus’ long backbone was supported by muscles. So that the neck and tail could move easily, a tendon probably ran along the length of its backbone.
Diplodocus could fight off predators with its powerful whiplash tail, or rear up on its back legs using its tail as support. This freed the dinosaur’s massive front legs for defence. A large, curved claw on the inner toe could also be used as a sharp weapon.
Diplodocus’ neck was not as long as that of its Chinese cousin, Mamenchisaurus. Compared to the latter’s neck, which was 11m long, Diplodocus’neck was ‘only’ 7.5m long and its enormous weight was balanced by a long tail, which stopped the giant from tipping over. The bones that were hidden beneath Diplodocus’ skin and muscle were designed for strength and support, rather than speed.
In 2004, a presentation at the annual conference of the Geological Society of America made a case for Seismosaurus being a junior synonym of Diplodocus. This was followed by a much more detailed publication in 2006, which not only renamed Seismosaurus as Diplodocus hallorum, but also speculated that it could prove to be the same as D. longus.