The giant size of Argentinosaurus and other sauropods was likely made possible by a combination of factors; these include fast and energy-efficient feeding allowed for by the long neck and lack of mastication, fast growth and fast population recovery due to their many small offspring.
Advantages of giant sizes would likely have included the ability to keep food inside the digestive tract for lengthy periods to extract a maximum of energy, and increased protection against predators.
Sauropods were oviparous (egg-laying).
In 2016, Mark Hallett and Matthew Wedel stated that the eggs of Argentinosaurus were probably only 1 litre (0.26 US gal) in volume, and that a hatched Argentinosaurus was no longer than 1 metre (3.3 ft) and not heavier than 5 kilograms (11 lb).
The largest sauropods increased their size by five orders of magnitude after hatching, more than in any other amniote animals.
Hallett and Wedel argued size increases in the evolution of sauropods were commonly followed by size increases of their predators, theropod dinosaurs.
Argentinosaurus might have been preyed on by Mapusaurus, which is among the largest theropods known.
Mapusaurus is known from at least seven individuals found together, raising the possibility that this theropod hunted in packs to bring down large prey including Argentinosaurus.

In 2013, Sellers and colleagues used a computer model of the skeleton and muscles of Argentinosaurus to study its speed and gait.
Before computer simulations, the only way of estimating speeds of dinosaurs was through studying anatomy and trackways.
The computer model was based on a laser scan of a mounted skeletal reconstruction on display at the Museo Carmen Funes.
Muscles and their properties were based on comparisons with living animals; the final model had a mass of 83 tonnes (91 short tons).
Using computer simulation and machine learning techniques, which found a combination of movements that minimised energy requirements, the digital Argentinosaurus learned to walk.
The optimal gait found by the algorithms was close to a pace (forelimb and hind limb on the same side of the body move simultaneously).
The model reached a top speed of just over 2 m/s (7.2 km/h, 5 mph).
The authors concluded with its giant size, Argentinosaurus reached a functional limit.
Much larger terrestrial vertebrates might be possible but would require different body shapes and possibly behavioural change to prevent joint collapse.
The authors of the study cautioned the model is not fully realistic and too simplistic, and that it could be improved in many areas.
For further studies, more data from living animals is needed to improve the soft tissue reconstruction, and the model needs to be confirmed based on more complete sauropod specimens.
The giant size of Argentinosaurus and other sauropods was likely made possible by a combination of factors; these include fast and energy-efficient feeding allowed for by the long neck and lack of mastication, fast growth and fast population recovery due to their many small offspring. Advantages of giant sizes would likely have included the ability to keep food inside the digestive tract for lengthy periods to extract a maximum of energy, and increased protection against predators. Sauropods were oviparous (egg-laying). In 2016, Mark Hallett and Matthew Wedel stated that the eggs of Argentinosaurus were probably only 1 litre (0.26 US gal) in volume, and that a hatched Argentinosaurus was no longer than 1 metre (3.3 ft) and not heavier than 5 kilograms (11 lb). The largest sauropods increased their size by five orders of magnitude after hatching, more than in any other amniote animals. Hallett and Wedel argued size increases in the evolution of sauropods were commonly followed by size increases of their predators, theropod dinosaurs. Argentinosaurus might have been preyed on by Mapusaurus, which is among the largest theropods known. Mapusaurus is known from at least seven individuals found together, raising the possibility that this theropod hunted in packs to bring down large prey including Argentinosaurus.
In 2013, Sellers and colleagues used a computer model of the skeleton and muscles of Argentinosaurus to study its speed and gait. Before computer simulations, the only way of estimating speeds of dinosaurs was through studying anatomy and trackways. The computer model was based on a laser scan of a mounted skeletal reconstruction on display at the Museo Carmen Funes. Muscles and their properties were based on comparisons with living animals; the final model had a mass of 83 tonnes (91 short tons). Using computer simulation and machine learning techniques, which found a combination of movements that minimised energy requirements, the digital Argentinosaurus learned to walk. The optimal gait found by the algorithms was close to a pace (forelimb and hind limb on the same side of the body move simultaneously). The model reached a top speed of just over 2 m/s (7.2 km/h, 5 mph). The authors concluded with its giant size, Argentinosaurus reached a functional limit. Much larger terrestrial vertebrates might be possible but would require different body shapes and possibly behavioural change to prevent joint collapse. The authors of the study cautioned the model is not fully realistic and too simplistic, and that it could be improved in many areas. For further studies, more data from living animals is needed to improve the soft tissue reconstruction, and the model needs to be confirmed based on more complete sauropod specimens.
Argentinosaurus