Dinosaurs A to Z
Diplodocidae

Diplodocus carnegii dih-PLOD-oh-kus

"Double beam"

Diplodocus silhouette
You 1.8 m (5.9 ft) tall
Diplodocus 26 m (85 ft) long
as long as 15 people standing fingertip to fingertip
silhouette · Elihu Guzmán Arroyo (CC-BY) via PhyloPic
Length
26 m (85 ft) — About 26 m long, ~15 tonnes — one of the longest dinosaurs known.
Period
Late Jurassic (155–145 Mya)
Place
North America · Western United States
Food
Herbivore — Low-growing plants, ferns, and possibly conifer needles raked off branches.
Clade
Diplodocidae Dinosauria Saurischia Sauropodomorpha Sauropoda Whip-tailed sauropods: Diplodocus, Apatosaurus, Brontosaurus.

A whip-tailed giant whose name comes from the "double beams" under its tail.

Diplodocus was a sauropod built like a 26-meter-long suspension bridge. Its neck and tail balanced on hips supported by pillar-like legs, the whole structure held off the ground by tension between front and back. The tail ended in a thin whip — possibly used to make sonic booms to scare off predators, though this is debated.

More about Diplodocus

Discovery

Named by Othniel Charles Marsh (who coined the genus name; first fossils found by S. W. Williston) · 1878 · mid-western North America, in the Morrison Formation

The first fossils were discovered in 1877 by S. W. Williston, and Marsh coined the genus name Diplodocus in 1878. It became one of the more common dinosaur fossils found in the middle to upper Morrison Formation.

The name is a Neo-Latin term from Greek diplos ("double") and dokos ("beam"), referring to the double-beamed chevron bones under the tail, which were once thought to be unique.

Portrait of Othniel Charles Marsh
Othniel Charles Marsh The paleontologist who coined the name Diplodocus in 1878.
For the curious → How did Diplodocus feed with its odd peg-like teeth?
Its small, peg-like teeth pointed forward and sat only at the front of the jaws, and the wear patterns are unusual for a sauropodA giant, long-necked, four-legged plant-eater like Brachiosaurus.. Unilateral branch stripping is the most likely feeding behavior, where one tooth row stripped foliage while the other acted as a guide. However, a 2012 biomechanical study found that a bark-stripping scenario was not supported, since the skull and teeth would undergo extreme stresses.
For the curious → Could such a huge animal breathe efficiently?
Scientists have debated how sauropods breathed given their large bodies and long necks, which increased dead space. They likely had an avian respiratory system, which is more efficient than mammalian or reptilian ones, and reconstructions of the neck and thorax show great pneumaticity that may have aided respiration as it does in birds.

What we know

  • Longest neck-to-tail of any well-known dinosaur — about 26 m end to end.
  • Skull was small relative to body, with peg-shaped teeth at the front only.
  • Tail had over 80 vertebrae, ending in a thin whip-like tip.
  • Lived in the Morrison Formation alongside Allosaurus, Apatosaurus, Stegosaurus.

What we guess

  • How the neck was held — long debate between high-browsing and low-sweeping postures.
  • Whether the whip tail could break the sound barrier (one paper says yes; many skeptical).
  • How it gathered enough food to feed its enormous body — chewing was minimal, gut fermentation key.