Named By: Othniel Charles Marsh - 1877.
Synonyms: Titanosaurus montanus.
Classification: Chordata, Reptilia, Dinosauria, Saurischia, Sauropoda, Diplodocoidea, Apatosaurinae.
Species: A. montanus (type).
Known locations: USA, Colorado - Morrison Formation.
Time period: Late Jurassic.
Fossil representation: Two vertebrae.
Atlantosaurus was named by Othniel Charles Marsh in 1877, though his first choice of name was Titanosaurus. However, Titanosaurus had actually been established as a genus name by Richard Lydekker earlier that same year, so Marsh renamed his fossils as Atlantosaurus. At the time of their original naming, the two vertebrae that are the holotype fossils of Atlantosaurus were noted as having air pockets, something that made them unique for the time. In modern times however, these air sacs have been noted as being generic of all sauropod dinosaurs, which means that the holotype vertebrae of Atlantosaurus are not distinctive of a specific genus, which in turn is why Atlantosaurus is treated as a dubious genus of sauropod. Further to this, the vertebrae of Atlantosaurus are noted as being to a diplodocoid sauropod, possibly a robust morph known as an apatosaurine. In simpler terms this means that Atlantosaurus was similar to the famous Apatosaurus (often referred to as Brontosaurus), though Atlantosaurus may actually even be synonymous with Apatosaurus.
- Notice of new dinosaurian reptiles from the Jurassic formation. American Journal of Science and Arts 14:514-516. - O. C. Marsh - 1877.
- Skull and relationships of the Upper Jurassic sauropod Apatosaurus (Reptilia, Saurischia). - Bulletin of the Carnegie Museum, 8: 1–35. - D. S. Berman & J. S. McIntosh - 1978.