Diplodocus is an extinct genus of diplodocid sauropod dinosaurs known from the Late Jurassic of North America. The first fossils of Diplodocus were discovered in 1878 by S. W. Williston. 

Family: †Diplodocidae

Subfamily: †Diplodocinae

Scientific name: Diplodocus (Double beam)

Extinction status: Extinct Encyclopedia of Life

Class: Reptilia

Diplodocus: Facts About the Longest Dinosaur

One of the longest dinosaurs, Diplodocus had a unique body construction, with two rows of bones on the underside of its tail to provide extra support and greater mobility.

Because of Diplodocus' unusual skeleton, paleontologist Othniel C. Marsh coined its name in 1878, deriving it from the Greek words "diplos," meaning "double," and "dokos" meaning "beam."

One of the best-known sauropods (long-necked herbivorous dinosaurs), this genus of dinosaur lived during the late Jurassic Period, about 155.7 million to 150.8 million years ago, and primarily roamed western North America. Four species are recognized: D. longus, D. carnegii, D. hayi and D. hallorum (previously known as Seismosaurus).

The name Diplodocus means "double beam" in Greek. It was inspired by the two long parallel protrusions, called "chevrons," that appear on the bottom of some of the tail vertebrae. Diplodocus longus was an exceptionally long dinosaur whose skeleton was made up of almost 300 bones. However, its tail alone was comprised of about 80 vertebral bones (bones from the spinal column). That means that almost one-third of a Diplodocus's body was just tail!

Based on the length of its skeleton, scientists estimate that the average Diplodocus probably measured about 80 feet (24.3 meters) long as an adult. Excavations of the Carnegie Quarry at Dinosaur National Monument produced 3 of the best Diplodocus longus skeletons ever found. One specimen found at the monument included 82 of the dinosaur's tail bones still connected in the right order as they would have been in life. The last third of Diplodocus's tail tapers down to a "whiplash," made up of very tiny bones.