Diplodocus is a genus of diplodocid sauropod dinosaur 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 διπλόος (diploos) "double" and δοκός (dokos) "beam", in reference to its double-beamed chevron bones located in the underside of the tail. These bones were initially believed to be unique to Diplodocus; however, they have since then been discovered in other members of the diplodocid family and in non-diplodocid sauropods such as Mamenchisaurus.

It lived in what is now western North America at the end of the Jurassic Period. Diplodocus is one of the more common dinosaur fossils found in the Upper Morrison Formation, a sequence of shallow marine and alluvial sediments deposited about 150 to 147 million years ago, in what is now termed the Kimmeridgian and Tithonian stages. The Morrison Formation records an environment and time dominated by gigantic sauropod dinosaurs such as Camarasaurus, Barosaurus, Apatosaurus and Brachiosaurus.

Diplodocus is among the most easily identifiable dinosaurs, with its classic dinosaur shape, long neck and tail and four sturdy legs. For many years, it was the longest dinosaur known. Its great size may have been a deterrent to the predators Allosaurus and Ceratosaurus: their remains have been found in the same strata, which suggests they coexisted with Diplodocus.

Discovery and speciesEdit

Several species of Diplodocus were described between 1878 and 1924. The first skeleton was found at Como Bluff, Wyoming by Benjamin Mudge and Samuel Wendell Williston in 1878, and was named Diplodocus longus ('long double-beam'), by paleontologist Othniel Charles Marsh in 1878.[18] Diplodocus remains have since been found in the Morrison Formation of the western U.S. States of Colorado, Utah, Montana and Wyoming. Fossils of this animal are common, except for the skull, which is often missing from otherwise complete skeletons. Although not the type species, D. carnegii is the most completely known and most famous due to the large number of casts of its skeleton in museums around the world.

The two Morrison Formation sauropod genera Diplodocus and Barosaurus had very similar limb bones. In the past, many isolated limb bones were automatically attributed to Diplodocus but may, in fact, have belonged to Barosaurus.

Valid speciesEdit

  • Diplodocus hallorum (formerly known as Seismosaurus)
  • D. longus, the type species, is known from two skulls and a caudal series from the Morrison Formation of Colorado and Utah.
  • D. carnegii (also spelled D. carnegiei), named after Andrew Carnegie, is the best known, mainly due to a near-complete skeleton collected by Jacob Wortman, of the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania and described and named by John Bell Hatcher in 1901.
  • D. hayi, known from a partial skeleton discovered by William H. Utterback in 1902 near Sheridan, Wyoming, was described in 1924.
  • D. hallorum, first described in 1991 by Gillette as Seismosaurus halli from a partial skeleton comprising vertebrae, pelvis and ribs. George Olshevsky later attempted to emend the name as S. hallorum, citing incorrect grammar on the part of the original authors, a recommendation that has been followed by others, including Carpenter (2006). 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 the species Diplodocus hallorum, but also speculated that it could prove to be the same as D. longus. The position that D. hallorum should be regarded as a specimen of D. longus was also taken by the authors of a redescription of Supersaurus, refuting a previous hypothesis that Seismosaurus and Supersaurus were the same.


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