Diplodocus was gigantic dinosaurs found in North America as fossils from the Late Jurassic Period Diplodocus is perhaps the most commonly displayed dinosaur. It, along with sauropods such as Apatosaurus, belongs to a related subgroup of dinosaurs called diplodocids, members of which were some of the longest land animals that ever lived.

The skull of Diplodocus was unusually small and rather light. Elongate like that of a horse, it sat atop a very long neck; the brain was extremely small. The body was comparatively light and was well supported by limb girdles and pillarlike legs. While most of these dinosaurs weighed slightly more than 30 tons, some members of the genus may have weighed as much as 80 tons.