Argentinosaurus

Argentinosaurus huinculensis was a giant titanosaur and among the largest terrestrial animals ever to exist. The available fossil evidence is fragmentary. The holotype includes several dorsal vertebrae, a sacrum, ribs, a partial fibula, and a large femur. Researchers have reconstructed the rest of its body by studying more complete relatives like Patagotitan and Notocolossus and extrapolating from known skeletal proportions.

Despite the scarcity of remains, the individual bones are extraordinary in scale. The vertebrae exceed 1.5 m in height, while the femur reaches approximately 2.5 m. Estimates for the animal's total length have fluctuated between 30 and 40 m, though current consensus suggests a range of 30–35 m. Mass estimates also vary. Most recent studies place the dinosaur's weight between 65 and 80 tonnes, viewing higher published figures of over 90 tonnes as overestimates.

Phylogenetically, Argentinosaurus is classified as a derived titanosaur within Lognkosauria. This clade also includes Patagotitan, Puertasaurus, and Notocolossus. These giants were the primary herbivores of Cretaceous Gondwana and represent some of the largest dinosaurs in the fossil record.

An 80-tonne adult Argentinosaurus likely faced few natural threats. Predation was probably limited to young or sick individuals targeted by large allosauroids like Mapusaurus. Based on the bone histology of its relatives, Argentinosaurus may have taken 30–40 years to reach its full size from a tiny 5 kg hatchling. This rapid growth allowed juveniles to quickly move beyond the most vulnerable size classes. Fossil trackways from titanosaur-rich sites in Gondwana suggest that these animals travelled in herds. Their long necks allowed them to feed high in the conifer canopy, while their long tails served as a biomechanical counterbalance.

• MCF-PVPH-1 — holotype, Museo Carmen Funes, Plaza Huincul, Argentina; partial postcranium.
• Possible referred material from same and nearby Huincul Formation localities.
• Comparative material from close relatives Patagotitan and Notocolossus.

Maximum body mass — published estimates range from ~50 to ~96 tonnes; the most defensible modern estimates are 65–80 tonnes. Total length — 30–35 m by current consensus, less than some early estimates. Comparison with Patagotitan — Patagotitan (described 2017) is a close relative with more complete material; mass estimates of the two are now considered roughly similar, with the title of "largest" likely shifting between them depending on which body region is reconstructed and how. Comparison with even larger fragmentary giants (Bruhathkayosaurus, Maraapunisaurus) — almost impossible to test definitively given how little material exists.

Argentinosaurus is the standard "biggest dinosaur" answer in popular media. It appears in Walking with Dinosaurs: Land of Giants (2002), Prehistoric Planet (2023, Season 2), and many recent dinosaur publications.

• sauropodomorpha
• patagotitan
• brachiosaurus
• diplodocus

• Bonaparte, J. F., & Coria, R. A. (1993). Un nuevo y gigantesco saurópodo titanosaurio de la Formación Río Limay (Albiano-Cenomaniano) de la Provincia del Neuquén, Argentina. Ameghiniana, 30, 271–282.
• Carballido, J. L., et al. (2017). A new giant titanosaur sheds light on body mass evolution among sauropod dinosaurs. Proc. R. Soc. B, 284, 20171219.
• Mazzetta, G. V., Christiansen, P., & Fariña, R. A. (2004). Giants and bizarres: body size of some southern South American Cretaceous dinosaurs. Historical Biology, 16, 71–83.
• Sellers, W. I., et al. (2013). March of the titans: the locomotor capabilities of sauropod dinosaurs. PLOS ONE, 8, e78733.