Fossil range: Late Jurassic, 150 Mya
Scientific classification












Marsh, 1877


  • A. ajax Marsh, 1877 (type)
  • A. excelsus (Marsh, 1879c) Riggs, 1903
  • A. louisae Holland, 1915
  • A. parvus (Peterson & Gilmore, 1902)


  • Brontosaurus Marsh, 1879c
  • Elosaurus Peterson & Gilmore, 1902

Apatosaurus, including the popular, but obsolete synonym Brontosaurus, is a genus of extinct sauropod dinosaur that lived about 150 million years ago, during the Jurassic Period (Kimmeridgian and Tithonian ages). It was one of the largest land animals that ever existed, with an average length of 23 meters (75 ft) and a mass of at least 23 metric tons (25 short tons). The name Apatosaurus means 'deceptive lizard', so-given because the chevron bones were similar to those of a prehistoric marine lizard, Mosasaurus.

The cervical vertebrae were less elongated and more heavily constructed than those of Diplodocus and 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.

Fossils of this animal have been found in Nine Mile Quarry and Bone Cabin Quarry in Wyoming and at sites in Colorado, Oklahoma and Utah, USA.


The composite term Apatosaurus comes from the Greek words apate (ἀπάτη)/apatelos (ἀπατηλός) meaning "deception"/"deceptive" and sauros (σαῦρος) meaning "lizard"; thus, "deceptive lizard". Paleontologist Othniel Charles Marsh (1831–1899) gave it this name, because he regarded the chevron bones as similar to those of some mosasaurs, members of a group of prehistoric marine lizards. The synonym genus of A. excelsus, Brontosaurus, comes from the Greek words bronto (βροντή), meaning "thunder", and sauros (σαῦρος) meaning "lizard".


Apatosaurus was a large, long-necked quadrupedal animal with a long, whip-like tail. Its forelimbs were slightly shorter than its hindlimbs. It was roughly the weight of four elephants.[5] Most size estimates for Apatosaurus are based on the type specimen of A. louisae, CM3018, which is mostly estimated at 23 m (75 ft) in length,[6] mass estimates on the other hand, have been as high as 35 t (39 short tons) for A. louisae[7] and 26 t (29 short tons) for A. excelsus.[8] However, more recent estimates using 3D models and more complex regression equations give a range of 16.4–22.4 t (18–25 short tons) in weight for the larger A. louisae.

The skull was small in comparison with the size of the animal. The jaws were lined with spatulate (chisel-like) teeth, suited to an herbivorous diet. Like those of other sauropods, the vertebrae of the neck were deeply bifurcated; that is, they carried paired spines, resulting in a wide and deep neck.[9] 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. The shape of the tail is unusual for a diplodocid, being comparatively slender, due to the vertebral spines rapidly decreasing in height 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.[10] Apatosaurus had a single large claw on each forelimb, and the first three toes possessed claws on each hindlimb. The phalangeal formula is 2-1-1-1-1, meaning that the innermost finger (phalange) on the forelimb has two bones, the next has one, etc.

Classification and speciesEdit

External linksEdit

Mantell's Iguanodon restoration

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