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Temporal range: Upper Jurassic
A. louisae skeleton, Carnegie Museum
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
Superorder: Dinosauria
Order: Saurischia
Suborder: Sauropodomorpha
Infraorder: Sauropoda
Family: Diplodocidae
Genus: Apatosaurus
Marsh, 1877

Apatosaurus was a sauropod dinosaur which lived in the late Jurassic period. It was known before as Brontosaurus.

It grew as big as 21 meters long, 4.5 meters tall at the hip, and weighed up to 23 metric tons. It ate plants. The bones of Apatosaurus have been found in Wyoming, Colorado, Oklahoma, and Utah in the United States.

When it was first found, scientists thought that Apatosaurus lived partly under water, since it could not hold its own weight on dry land. Now they think it lived on dry land, probably in herds.

The cervical vertebrae were less elongated and more solid than those of Diplodocus. The bones of the leg were much stockier (despite being longer), implying a more robust animal. The tail was held above the ground during normal locomotion. Like most sauropods, Apatosaurus had only a single large claw on each forelimb, with the first three toes on the hind limb possessing claws.

There are three species of Apatosaurus:

  • A. ajax was discovered by Othniel Charles Marsh in 1877.
  • A. excelsus (originally named Brontosaurus excelsus) was discovered by Marsh in 1879.
  • A. louisae was discovered by William Holland in 1915.
  • Another dinosaur species discovered in 1994 was at first named A. yahnahpin, but in 1998, it was renamed Eobrontosaurus yahnahpin.

The Brontosaurus story[change | change source]

Brontosaurus (meaning "thunder lizard") was a dinosaur which is now considered to be Apatosaurus. Othniel Charles Marsh described it as a new type of dinosaur.

The Brontosaurus became exceedingly popular, and the name "Brontosaurus" is often applied to the Apatosaurus. Some argued it should be called Apatosaurus as early as 1903, while others at the same time felt that the name Brontosaurus should be a synonym for Apatosaurus. Most agreed with this by the 1970s, but some books still use the old name.