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.

[3] Marsh soon learned that the name Titanosaurus had already been used earlier that year by Richard Lydekker to describe a different sauropod from India, so he renamed it Atlantosaurus montanus.

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.

[2][6] In 1878, Marsh named a second species, Atlantosaurus immanis, "the immense one", based on holotype YPM 1840, a nearly complete postcranial skeleton, also found by Lakes, in Quarry Number 10.

immanis was in 2015 identified as a dubious member of the Apatosaurinae separate from Apatosaurus and Brontosaurus, but did not examine its relationship with Atlantosaurus montanus.