Diplodocus
Diplodocus is a genus of diplodocid sauropod dinosaurs, whose fossils were first discovered in 1877 by S. W. Williston. The generic name, coined by Othniel Charles Marsh in 1878, is a neo-Latin term derived from Greek διπλός "double" and δοκός "beam", in reference to the double-beamed chevron bones located in the underside of the tail, which were then considered unique. The genus of dinosaurs lived in what is now mid-western North America, at the end of the Jurassic period. It is one of the more common dinosaur fossils found in the middle to upper Morrison Formation, between about 154 and 152 million years ago, during the late Kimmeridgian Age. The Morrison Formation records an environment and time dominated by gigantic sauropod dinosaurs, such as Apatosaurus, Barosaurus, Brachiosaurus, Brontosaurus, and Camarasaurus.