Diplodocus carnegii was a sauropod dinosaur that roamed the savannas of North America during the Late Jurassic Period, between 154 and 152 million years ago. It was related to the more famous Brontosaurus and Apatosaurus with whom it would have coexisted, yet had a significantly lighter build, weighing little more than sixteen tons. Nonetheless, Diplodocus is among the longest dinosaurs known from a complete skeleton, stretching up to 85 feet from head to tail.