Temporal range: Late Jurassic
An artist's illustration of Apatosaurus ajax
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
Superorder: Dinosauria
Order: Saurischia
Suborder: Sauropodomorpha
Family: Diplodocidae
Subfamily: Apatosaurinae
Genus: Apatosaurus
Marsh, 1877
Type species
Apatosaurus ajax
Marsh, 1877
Referred species
  • Apatosaurus louisae (Holland, 1916)

Apatosaurus ajax (meaning "deceptive lizard") is an extinct genus of sauropod dinosaurs that lived about 152-151 million years ago (mya), during the Tithonian age of the Late Jurassic period. It was one of the large sauropods, about 4.5 meters (15 feet) tall at the hips, with a length of up to 22-27 meters (75-90 feet) and a mass up to 35 metric tonnes (39 tons).



It was once believed that Apatosaurus was too massive to support its own weight on dry land, so it was theorized that the sauropod must have lived partly submerged in water, perhaps in a swamp. The findings do not support this and debunked this speculation. In fact, like its relative Diplodocus, Apatosaurus was a grazing animal with a very long neck, and a long tail that served as a counterweight. Fossilized footprints indicate that it probably lived in herds. To aid in processing food, Apatosaurus may have swallowed gizzard stones (gastroliths) the same way many birds do today — its jaws alone were not sufficient to chew tough plant fibers, a common sight in many Diplodocid animals during the Late Jurassic. So it might've grazed on soft marshy reeds or thin plant stalks.

A modern view of Apatosaurus

Classification and history

In 1877, Othniel Charles Marsh published notes on his discovery of the Apatosaurus, and then in 1879 described another, more complete dinosaur — the Brontosaurus. In 1903, it was discovered that the apatosaur was in fact a juvenile brontosaur, and the name Apatosaurus, having been published first, was deemed to have priority as the official name; Brontosaurus was relegated to being a synonym. The name was not formally removed from the records of paleontology until 1974. In 2015, the name Brontosaurus was assigned to its own genus due to a study proving that Apatosaurus and Brontosaurus were different. Fossils of this animal have been found in Nine Mile Quarry and Bone Cabin Quarry in Wyoming, and at sites in Colorado, Oklahoma, Utah, USA.


  • A. ajax is the type species of the genera, and was named by the paleontologist Othniel Charles Marsh in 1877 after Ajax, the hero from Greek mythology. It is the holotype for the genera, and two partial skeletons have been found including part of a skull.
  • A. louisae was named by William Holland, in 1915. It is known from one partial skeleton, which was found in Colorado, in the United States.

Robert T. Bakker made A. yahnahpin the type species of a new genus, Eobrontosaurus in 1998, so it is now properly Eobrontosaurus yahnahpin. It was named by Filla, James and Redman in 1994. One partial skeleton has been found in Wyoming. In 2015, the species was assigned to Brontosaurus.


Apatosaurus was a large, long-necked quadrupedal animal with a long, whip-like tail, possibly for sef-defense against predators, forelimbs were slightly shorter than its hindlimbs. One measurement places the total length of the species Apatosaurus louisae at 21.8 m (72 ft).[3]

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It was roughly the weight of four elephants. Estimates for A. louisae were 20,600 kg (45,000 lb)[3] and 22,407 kg (49,400 lb).Other estimates of the body mass of adult Apatosaurus species range from 18,000 kg (40,000 lb) to 35,000 kg (77,000 lb). A microscopic study of Apatosaurus bones concluded that the animals grew rapidly when young and reached near-adult sizes in about 10 years.

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The skull was small in comparison with the size of the animal. The jaws were lined with spatulate teeth, which resembled chisels, suited to an herbivorous diet. Like other sauropods, the vertebrae of the neck were deeply bifurcated; that is, they carried paired spines, creating a wide and deep profile for the neck. The apparently massive neck was, however, filled with an extensive system of weight-saving air sacs. Apatosaurus, like its close relative Supersaurus, is notable for the incredibly tall spines on its vertebrae, which make up more than half the height of the individual bones. Also unusual among diplodocids is the shape of the tail, which is comparatively thin in breadth and short in height, a profile caused by the vertebral spines decreasing in height rapidly the farther they are from the hips. Apatosaurus also had very long ribs compared to most other diplodocids, giving it an unusually deep chest. The limb bones were also very robust. An article that appeared in the November 1997 issue of Discover Magazine reported research into the mechanics of Apatosaurus tails by Nathan Myhrvold, a computer scientist from Microsoft. Myhrvold carried out a computer simulation of the tail, which in diplodocids like Apatosaurus was a very long, tapering structure resembling a bullwhip. This computer modeling suggested that sauropods were capable of producing a whip-like cracking sound of over 200 decibels, comparable to the volume of a cannon firing.

In popular culture

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  • Apatosaurus is one of the most recognizable dinosaurs. It has appeared a lot of times in pop culture.
  • Apatosaurus appeared in the BBC film 'The Ballad of Big Al' (or Allosaurus), as a background dinosaur. It appears to share a similar model to the Diplodocus from Walking with Dinosaurs. Only the Apatosaurus don't have spines and is a reskin of color. The head of the BBC Apatosaurus is very similar to the Diplodocus.
  • Apatosaurus also appeared in The Good Dinosaur, The protagonist Arlo being an Apatosaurus.
  • Apatosaurus appears as a background dinosaur in Jurassic World, although it has a major scene where one died by its wounds from the Indominus rex. A teaser for the Jurassic World: Fallen Kingdom reveals that five more Apatosaurus have managed to survived the rampage of the Indominus rex before her death, but they and the other dinosaurs will now face a new danger in the form of an impending volcanic eruption.
  • Apatosaurus is featured in Jurassic World: Alive, as a common dinosaur, and also the dinosaur with the highest health ranking.
  • Apatosaurus does appear in Jurassic World: Evolution, seen in several trailers, and can be mined in dig sites across Western North America.
  • Originally, only Apatosaurus skeleton and a statue of it could be purchased as decorations for Jurassic World: The Game, but after the June 29, 2016 update, it became a cloneable VIP dinosaur in the solid gold pack.
  • Fortnite: Battle Royale has a sauropod banner icon that may be an Apatosaurus.
  • Littlefoot the Apatosaurus is one of the main character dinosaurs in the famed The Land Before Time movies.
  • Apatosaurus made an appearance in the Roblox game called "Dinosaur Simulator".
  • In the upcoming movie Jurassic World: Dominion, the Apatosaurus is seen in the trailer