Not in the picture: palentologists debating its gait.
All this info below is from Tom Rea's Bone Wars; chapter 15, Heads and Tails, specifically:
Basically in the early 1900s scientists thought Diplodocuses lived in swamps, the water helping them moving their massive bodies around (p.191). They speculated they ate soft algae on the shores. Since then much research has been done: diplodocuses have been thought to be basically giraffes: walking on dry land and standing on its hind legs and using the tail as support to eat leaves far up (p.192f). However, latest science suggests the earlier scientists conclusion was partially right. It would have been easier for a Diplodocus to chew the soft plants closer to the ground, and they might very well have eaten shore algae and water plants (p.196f). This also solves certain blood-pressure problems coming from being such a big animal. Tom Rea describes them as basically "great, long-necked water buffaloes" (p.197), an image I really, really love.
