These remains were unearthed by Argentine paleontologist José Bonaparte in 1983 during an expedition by the Museo Argentino de Ciencias Naturales and later described as a new genus and species, Amargatitanis macni by Sebastián Apesteguía.

During an expedition by the Museo Argentino de Ciencias Naturales from March 11th to 16th of 1983, Argentine paleontologist José Bonaparte collected several fossils from four sites along the La Amarga stream in Neuquén, Argentina.

[1][3] It was originally assigned to the group Titanosauria due to the anatomy of the scapula and caudal vertebra, but a 2016 reanalysis of the holotype (MACN PV N53) fossils demonstrated that Amargatitanis was instead a dicraeosaurid dipolodocoid.

The study, authored by researcher Pablo Gallina, also removed MACN PV N34 and N51 from the holotype material, which were referred to an indeterminate titanosauriform, and considered only the dicraeosaurid bones to be from the genus.

[4][5][6] Amargatitanis macni is known from a single specimen, the holotype MACN PV N53, which was found in the Barremian-aged Puesto Antigual Member of the La Amarga Formation, approximately 129 to 123 million years old.

The prezygapophyseal centrodiapophysial fossae, which are deep depressions on the anterior surface of the transverse processes of the caudal vertebrae found in most diplodocoids and some macronarians, differ from other sauropods in that they contain a thin vertical lamina (sheet of bone).

The distal end of the first metatarsal has an oval shape, rather than being constricted in the middle to form distinct medial and lateral condyles as in Dicraeosaurus.

[1] Apesteguía originally hypothesized in 2007 that Amargatitanis was a member of Titanosauria, a group of large, macronarian sauropods, based on features of the femur and scapula.

[17] A 2016 study by Pablo Gallina found that characteristics such as the lack of a lateral bulge on the femur and presence of procoelous vertebrae (centra being concave at the front and convex at the back) meant Amargatitanis belonged to the family Dicraeosauridae.

[15][5][1] In 2022, researcher Guillermo Windholz and colleagues argued that South American dicraeosaurids formed a clade based on their biogeography and results of phylogenetic analyses, with Amargatitanis being especially closely related to Pilmatueia and Bajadasaurus.

The results of their phylogenetic analyses are shown in the cladogram below:[5] Suuwassea Lingwulong Bajadasaurus Tharosaurus Pilmatueia Brachytrachelopan In a 2021 paper, two Argentine researchers, Guillermo J. Windholz and Ignacio A. Cerda, examined the bone histology of Amargatitanis using thin sections from a femur.

The six outermost growth marks are closely spaced, a structure known as an external fundamental system, indicating that the individual had not only reached sexual maturity but also its adult size.

[7] Amargatitanis stems from sedimentary rocks of the La Amarga Formation, which is part of the Neuquén Basin and dates to the Barremian and late Aptian of the Early Cretaceous.