reconstruction of A. giganteus, published in 1956 by Carlos Rusconi, was given a length around . In 1969, van Valen considered it as similar in size to Giraffatitan brancai (then called Brachiosaurus brancai). Based on an earlier mass estimate of G. brancai by Edwin Harris Colbert in 1962, van Valen gave A. giganteus an estimated mass of about . In 1994, Gregory S. Paul estimated the weight of both A. giganteus and Argentinosaurus at between and lengths of long. Extrapolating from the femur's parameters, a 2004 study by Gerardo Mazzetta and colleagues estimated the mass of A. giganteus at approximately ; slightly smaller than Argentinosaurus which in the same study was estimated at nearly . This would make A. giganteus among the heaviest known land animals. In 2006, Kenneth Carpenter used the relatively short-necked Saltasaurus as a guide and estimated a length of long. In an encyclopaedia supplementary, Thomas Holtz gave a length of 33 meters and an estimated weight equivalent to that of nine elephants, or around , assuming per elephant. In 2016, using equations that estimate body mass based on the circumference of the humerus and femur of quadrupedal animals, it was estimated to be in weight. In 2019, Gregory S. Paul estimated the mass of A. giganteus in the range, based on newer titanosaur reconstructions. In 2020 Molina-Pérez and Larramendi estimated its length at and its weight similar to Paul's estimation at . Due to the incompleteness of the remains, any size estimates are subject to a large amount of error. "Antarctosaurus" jaxarticus and "Antarctosaurus" brasiliensis "Antarctosaurus" jaxarticus and "Antarctosaurus" brasiliensis are both known from very fragmentary remains. "Antarctosaurus" jaxarticus is known from a single femur which was briefly reported as resembling a femur attributed to Jainosaurus (then called "Antarctosaurus" septentrionalis). Paleontologist Teresa Maryańska noted that, whilst A. jaxarticus was named, it was not properly described or diagnosed. The femur possibly belongs to the titanosaur clade Lithostrotia. The type specimen of "Antarctosaurus" brasiliensis is only known from three fragmentary bones that are titanosaurian in nature; a partial left femur GP-RD-2, a partial right humerus GP-RD-3, and an incomplete dorsal vertebra (backbone) GP-RD-4. The femur is preserved and was estimated at if it were completed. The humerus is preserved and estimated at completed. The dorsal vertebra centrum is long. Classification Antarctosaurus has been included in few phylogenetic analyses, only being added to the matrix of Philip Mannion et