Anatomy: Diplodocus was a long-necked, whip-tailed giant with a tiny brain. It was about 90 feet (27 m) long, with a 26 foot (8 m) long neck and a 45 foot (14 m) long tail, but its head was less than 2 feet long. The nostrils were at the top of the head. It had peg-like teeth, but only towards the front of the jaws - there were no teeth in the back of the jaws. Diplodocus was more lightly built than the other giant sauropods, and may have weighed only about 10-20 tons.

When Diplodocus Lived: Diplodocus lived during the Jurassic period, about 156 million to 145 million years ago.

Diet: Diplodocus was an herbivore (a plant-eater). It ate plants, mostly conifers, using its peg-like teeth.

Fossils and Name: The first Diplodocus fossil was found by Earl Douglass and Samuel W. Williston in 1877 and was named by paleontologist Othniel C. Marsh in 1878. Many Diplodocus fossils have been found in the Rocky Mountains of the western USA (in Colorado, Montana, Utah, and Wyoming). Diplodocus means "Double-beamed," because it had bony protrusions running along its backbone.