Argentinosaurus

Argentinosaurus (meaning "lizard from Argentina") is a genus of giant sauropod dinosaur from the Early Cretaceous of what is now Argentina. It belongs to Titanosauria, the main sauropod group of the Cretaceous. Though known only from fragmentary fossils, it ranks among the largest land animals ever, measuring a certain length and weight.

The first bone—now thought to be a fibula—was found in 1987 by farmer Guillermo Heredia on his farm near Plaza Huincul, Neuquén Province. Believing it was petrified wood, he alerted the local Museo Carmen Funes, whose staff excavated it. In early 1989, Argentine palaeontologist José Bonaparte led a larger dig at the site, using pneumatic hammers to free bones from very hard rock. This yielded seven back vertebrae, the underside of the sacrum (including the first to fifth sacral vertebrae and some sacral ribs), and part of a flank rib. These became the holotype, catalogued MCF-PVPH 1. Bonaparte presented the find in 1989, and the formal description naming the genus and species *Argentinosaurus huinculensis* was published in 1993 by Bonaparte and Rodolfo Coria. The generic name means "Argentine lizard"; the specific name refers to Plaza Huincul. The 1987 limb bone was first described as a tibia but reidentified as a left fibula in 2004 by Gerardo Mazzetta and colleagues. In 1996, Bonaparte assigned a complete femur from the same locality to the genus, though it was crushed front-to-back. Mazzetta’s 2004 study also mentioned a second femur (shaft only) housed in the La Plata Museum. As of 2019, it remained uncertain whether either femur truly belonged to *Argentinosaurus*.

Interpretation is difficult due to the fragmentary nature. Debate centres on the position of the recovered vertebrae in the spinal column and whether they had accessory articulations that strengthened the spine. A computer model of the skeleton and muscles estimated a maximum speed of 7.2 km/h (5 mph) using a pace gait, where the fore and hind limb on the same side move together. The fossils come from the Huincul Formation, deposited in the Albian stage, which also contains the giant theropod *Mapusaurus* and other diverse dinosaurs.

Size estimates vary widely because the remains are incomplete. Palaeontologists compare the known material to smaller, more complete relatives and scale up. In 1994, Gregory Paul reconstructed a length of a certain figure. Later that year, Bonaparte and Coria estimated a hind limb length, trunk length, and overall body length. In 2006, Kenneth Carpenter used *Saltasaurus* as a guide to estimate length. In 2008, Jorge Calvo and colleagues used *Futalognkosaurus* proportions to suggest a shorter length. In 2013, William Sellers and colleagues measured the skeletal mount in the Museo Carmen Funes to estimate length and shoulder height. That same year, Scott Hartman proposed a different length.