Category: Dinosaur

Apatosaurus (A-pat-oh-sore-us), Deceptive Lizard, lived in the Late Jurassic of North America. Along with Diplodocus and Camarasaurus it is one of the most common dinosaurs found in the Morrison formation. It is popularly known by it junior synonym Brontosaurus. Many early finds were named based on limited fossil material that later turned out to have already been named. The first name takes priority.



Apatosaurus (XL Figure)

Apatosaurus (XL Figure)

Genera and Species


Sauropoda, Diplodocidae

Species: A. europaeus, A. maximus, A. amplexus, A. atrox, A. ferox, A. tendagurensis.

Senior synonyms: A. laticollis, Brontosaurus ajax, Atlantosaurus immanis, Atlantosaurus ajax, Atlantosaurus laticollis


Apatosaurus had thick skin for protection from its natural enemy, Allosaurus. Although shorter than Diplodocus it was much heavier, and had a proportionally shorter neck. It has been referred to as the fat Diplodocus. Adults were too large for any predators.


Length 21-23 meters (approximately 70-75 feet). Weight 1 - 1.7 tons.


It was a low to medium browser be could have had a greater range of motion in the neck allowing it to feed higher than Diplodocus. It appears to have been less social that Diplodocus. Adolescent animals have been found near adult fossils. Track ways seem to show groups of diplodocids of different sizes traveling together.

History of Discovery

Discovered by Marsh in 1877. It is known from complete skeletons, partial skeletons, skulls, and hundreds of other elements. Sauropod skulls are rare fossils, and diplodocid skulls are particularly fragile. Since Brontosaurus was robust animal it seemed intuitive that it would have a robust skull like the well documented Camarasaurus. Brontosaurus became famous thanks to the paintings and toys that show an Apatosaurus body with a Camarasaurus-like head. A complete skull was finally discovered in 1909, but the image of the stout-headed Brontosaurus still persisted well into the 20th century.


Found in North America (Utah and Colorado USA) in semi arid plains with forested rivers with a short rainy season.


  1. Paul, G. (2010). The Princeton Field Guide to Dinosaurs (pp. 10-12). Princeton, New Jersey: University Press Princeton.

  2. Worth, G. (1999). The Dinosaur Encyclopaedia (pp. 346). Scarborough, Western Australia: HyperWorks Reference Software.