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Temporal range: Late Jurassic, 150 Ma
Atlantosaurus montanus.jpg
Illustration of the sacrum
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Sauropodomorpha
Clade: Sauropoda
Family: Diplodocidae
Genus: Atlantosaurus
Marsh, 1877
Species: A. montanus
Binomial name
Atlantosaurus montanus
(Marsh, 1877)
  • ?A. immanis Marsh, 1878

Atlantosaurus (meaning "Atlas lizard") is a dubious genus of sauropod dinosaur. It contains a single species, Atlantosaurus montanus, from the upper Morrison Formation of Colorado, United States. Atlantosaurus was the first sauropod to be described during the infamous 19th century Bone Wars,[1] during which scientific methodology suffered in favor of pursuit of academic acclaim.[2]


The type specimen, found by Arthur Lakes in the Morrison Formation of Colorado, United States, was described by Othniel Charles Marsh, a Professor of Paleontology at Yale University (then called Yale College), in 1877 as Titanosaurus montanus. Marsh soon learned that the name Titanosaurus had already been used earlier that year to describe a different sauropod, so he renamed it Atlantosaurus montanus.[3] The skeletal remains discovered were initially distinguished by their immense size and by the pleurocoels (air-filled pockets) in the vertebrae. However, since the time of its discovery, these features have been found to be widespread among sauropods, making it nearly impossible to distinguish the two known vertebrae of Atlantosaurus from those of its relatives. Since it is unclear whether or not Atlantosaurus montanus actually represents a distinct species, it is considered a nomen dubium ("dubious name"),[4] though some researchers have considered it a likely synonym of Apatosaurus ajax.[2][5]


  1. ^ Wilson, J. A. (2011). "Anatomical terminology for the sacrum of sauropod dinosaurs." Contributions from the Museum of Paleontology, University of Michigan, 32(5): 59-69. [1]
  2. ^ a b Taylor, M.P. (2010). "Sauropod dinosaur research: a historical review." Pp. 361-386 in Moody, R.T.J., Buffetaut, E., Naish, D. and Martill, D.E. (eds.), Dinosaurs and Other Extinct Saurians: A Historical Perspective. London: The Geological Society, Special Publication No. 34.
  3. ^ Marsh, O.C. (December 1877). "Notice of New Dinosaurian Reptiles from the Jurassic formation" (PDF). American Journal of Science. 14 (84): 514–516. 
  4. ^ McIntosh, J. S. (1990). Sauropoda. In D. B. Weishampel, P. Dodson, and H. Osmólska (eds.), The Dinosauria, University of California Press, Berkeley, 345-401.
  5. ^ Berman, D.S. and McIntosh, J. S. (1978). "Skull and relationships of the Upper Jurassic sauropod Apatosaurus (Reptilia, Saurischia)." Bulletin of the Carnegie Museum, 8: 1–35.

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