Diplodocus: Facts About the Longest Dinosaur (2025)

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

Because ofDiplodocus'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. hayiandD. hallorum(previously known asSeismosaurus).

Diplodocusis the longest dinosaur known from a near-complete skeleton —that is, other dinosaurs, such as the sauropodSupersaurus, may be longer, but those length estimates are based on fairly incomplete skeletons.

The best-knownDiplodocusspecies,D. carnegii,of which there's a near-complete skeleton, was about90 feet (27.4 meters) long. The largest species,D. hallorum, was about 108 feet (33 m) long, according to a 2006 report in theNew Mexico Museum of Natural History Bulletins.

The majority ofDiplodocus'length was taken up by its neck and tail. For instance, the neck alone ofD. carnegiiwas at least 21 feet (6.5 meters) long, according to a 2011 study in theJournal of Zoology, and its tail was even longer.

Diplodocus' long tail possibly served as a counterbalance for its neck. A 1997 study in the journal Paleontology also found that diplodocids—dinosaurs in the Diplodocidae taxonomy family, which includesDiplodocusandApatosaurus(formerlyBrontosaurus) — couldwhip the tips of their tails at supersonic speeds, producing a canonlike boom, possibly to intimidate would-be attackers or rivals, or for communication and courtship.

Massive dinosaur

Estimating the mass of dinosaurs is often difficult, and modern estimates ofDiplodocus' mass (excludingD. hallorum) have ranged between 11 and 17.6 tons (10 to 16 metric tons). The dinosaur's large tail placed its center of mass pretty far back on its body, said David Button, a paleontologist at the University of Bristol in the United Kingdom.

"It seems that its center of mass is so far back that it wouldn't have been able to walk very quickly," Button told Live Science, adding that this center-of-mass position would have also made rearing up on its hind legs rather easy forDiplodocus.

Based on a 1910 reconstruction ofDiplodocusby paleontologist Oliver P. Hay, scientists initially thought thatDiplodocus'posture was more lizard-like, with splayed limbs,. However, paleontologist William J. Holland argued that such a posture would have required a large ditch to accommodate the dinosaur's stomach. In the 1930s,fossil footprints, or "trackways," suggestedDiplodocuswalked with its broad legs straight down, like an elephant.

Like some other sauropods,Diplodocus'nasal openings sat high up on its forehead instead of at the end of its snout. At one point, scientists thought thatDiplodocusmay have had a trunk. However, a 2006 study in the journal Geobios concluded thatDiplodocusdidn't have the neuroanatomy that could support a trunk, after comparing skulls of the dinosaur with those of elephants.

Another theory explainingDiplodocus'high nasal openings proposed the dinosaur needed this adaptation to live in water. But sauropods likely weren't suited for aquatic life, because they had pockets of air inside their bodies that would have made themtoo buoyant (and unstable)in deep water, according to a 2004 study in the journal Biology Letters

Diplodocushad five-toed broad feet, with the "thumb" toes sporting a claw that was unusually large, compared with other sauropods. It's not known what purpose this claw served forDiplodocusor other sauropods.

Fossilized skin impressionsdescribed in a 1992 Geology paper suggest that diplodocidsmay have had small, keratinous spines along their tails, bodies and necks.

Like other sauropods,Diplodocusprobably grew very quickly, reached sexual maturity at about 10 years of age, and continued to grow throughout life, according to a 2004 study in the journalOrganisms Diversity & Evolution.

No direct evidence ofDipolodocus'nesting habits exists, but it's possible the dinosaur, similar to other sauropods, laid its eggs in a communal area containing vegetation-covered shallow pits.

What did Diplodocus eat?

According to a 2009 article in the journal Acta Palaeontologica Polonica,Diplodocusprobably held its neck at a 45-degree angle most of the time. However, it's unclear if the animal had the neck flexibility that would allow it to reach both plants on the ground and leaves at the top of trees, without moving its body.

"Neck flexibility is a controversial topic in sauropods," Button said. Most recently, a 2014 study in the journal PeerJ suggestsDiplodocushad a very flexible neck, contrary to some previous research.

But even if the dinosaur couldn't lift its head up very high, it could still rear up on its hind legs to reach the top of tall trees, Button notes."It wouldn't have had much trouble low browsing and high browsing," he said.

Diplodocushad a number of small, forward-pointing, peglike teeth that were bunched in the front of its mouth. The teeth were slender and delicate, and replaced very quickly, Button said.

According to a 2013 study in the journal PLOS ONE, Diplodocushad a tooth-replacement rate of one tooth every 35 days, while the sauropodCamarasaurus, which lived in the same areas at the same time asDiplodocus, replaced one tooth every 62 days. The high tooth-replacement rate ofDiplodocussuggests the animal was eating abrasive food, such as soft plants that contained silica or grit-covered plants on the ground, Button said.

In 2012, Button and his colleagues sought to learn what, exactly,Diplodocuscould eat. Theymodeled the mechanical stressesthe animal would have experienced under normal biting, branch stripping and bark stripping behaviors, and found the animal wouldn't have been able to handle stripping bark from a tree, according to their study published in the journal Naturwissenschaften.

In a follow-up study, the researchers usedcranial biomechanical models to further investigate the dinosaurs' feeding habits, and try to determine how it could coexist withCamarasauruswhen both animals required a lot of sustenance and lived in a relatively resource-poor environment.

"Our main finding was that compared toCamarasaurus,Diplodocushad a weaker overall bite force," Button said. "It used very different jaw muscles that emphasized a horizontal rather than vertical movement, or sliding instead of hard biting."

This means that the two animals engaged in niche partitioning — they ate two completely different foods.Camarasaurus' skull and jaw were adapted to accommodating high stresses, allowing it to eat tough leaves and branches.Diplodocus, on the other hand, was more suited to eating ferns and stripping soft leaves off trees, Button said.

And rather than chewing,Diplodocusspent a considerable time fermenting its food in its expanded gut, and probably didn't use stones to help with digestion, Button said.

Fossil finds

The firstDiplodocusfossil was found near Cañon City, Colo., by Benjamin Mudge and Samuel W. Williston in 1877, and was named by Marsh in 1878.

A number ofDiplodocusfossils have been found in the Rocky Mountain region of Colorado, Montana, Utah and Wyoming, areas that are part of the fossil-rich Morrison Formation.

Thanks to steel magnate Andrew Carnegie, who donated casts of complete skeletons to various European monarchs,Diplodocusis among the most displayed dinosaur.Diplodocuscan been viewed at a number of museums worldwide, including the Carnegie Museum of Natural History in Pittsburgh and the Houston Museum of Natural Science.

In early 2015, London's Natural History Museum announced that it would be replacing its iconic Dippy — a replica of the near-completeD. carnegiifossil discovered in 1898 — with a model of a blue whale, the largest animal known to ever exist on Earth.

Related pages

• A Brief History of Dinosaurs

More dinosaurs

• Allosaurus: Facts About the 'Different Lizard'
• Ankylosaurus: Facts About the Armored Dinosaur
• Apatosaurus: Facts About the 'Deceptive Lizard'
• Archaeopteryx: Facts about the Transitional Fossil
• Brachiosaurus: Facts About the Giraffe-like Dinosaur
• Giganotosaurus: Facts about the 'Giant Southern Lizard'
• Spinosaurus: The Largest Carnivorous Dinosaur
• Triceratops: Facts about the Three-horned Dinosaur
• Tyrannosaurus Rex: Facts about T. Rex, King of the Dinosaurs
• Velociraptor: Facts about the 'Speedy Thief'

Time periods

Precambrian: Facts About the Beginning of Time

Mesozoic Era: Age of the Dinosaurs

• Jurassic Period Facts

• Pleistocene Epoch: Facts About the Last Ice Age
• Holocene Epoch: The Age of Man

Additional resources

• British Natural History Museum:Diplodocus
• Dinosaur National Monument:Diplodocus longus
• Read about the campaign to save Dippy