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Argentinosaurus

Argentinosaurus

Argentinosaurus is possibly the largest dinosaur of all time, based on fossil evidence, and generally speaking it is likely that it has been the largest terrestrial animal to ever walk the Earth. Since its discovery in 1987, paleontologists have debated its height and weight. Some reconstructions present this dinosaur as having a length ranging between 75 and 85 feet from head to tail and a weigh close to 75 tons while others less retained postulated that Argentinosaurus was nearly 100 feet long and weighed in the vicinity of 100 tons.

Argentinosaurus the titanosaurus

Titanosaurs
Titanosaurs

Given its gigantic size and the period in which it lived, Argentinosaurus is classified as a titanosaur, a family of sauropods with light armors which occupied all the continents of the globe during the Cretaceous era. In comparison, Argentinosaurus's closest titanosaur parent was Saltasaurus, which was much smaller in size at 10 tons and lived a few million years later.

Argentinosaurus lived during the Middle Cretaceous

As for the sauropod dinosaur giants, the first images that comes to mind in many people’s head are the Upper Jurassic behemoths of North America such as Diplodocus, Brachiosaurus and Apatosaurus. This is largely due to the fact that these are much more present in popular culture and especially in movies than their titanosaur counterparts. What distinguishes Argentinosaurus from these more familiar sauropods is that it lived more than 50 million years later during the Middle Cretaceous in a region of the world still poorly appreciated for its great diversity of dinosaurs, South America.

Undetermined posture

As is the case for the vast majority of long-necked sauropods and titanosaurs, with the exception of Brachiosaurus which stood like a giraffe, the question of what posture they adopted on a daily basis is still mysterious. Did Argentinosaurus hold its neck vertically to graze the top of the trees, or did it prefer a more horizontal position to forage near the ground? Like Diplodocus, it is possible that this dinosaur would stand on its hind legs for a short lapse of time before falling back on the ground, which more than likely caused seismic shock given its colossal size.

Other competitors for the title of biggest dinosaur ever

Argentinosaurus is not the only dinosaur at the top of the list for the title of the largest terrestrial animal, and not surprisingly all its rivals are also titanosaurs. Thus, depending on who performs the reconstruction and how fossil evidence are evaluated, many other titanosaurs aspire to that honor. The main competitors are the much lesser know Bruhathkayosaurus and Futalognkosaurus as well as the recently discovered Dreadnoughtus which enjoys growing popularity after making headlines in 2014 but whose size remains to be confirmed.

Fossil vertebra of Argentinosaurus

Argentinosaurus fossil
Argentinosaurus fossil

The first Argentinosaurus fossils were dug up by a South American breeder named Guillermo Heredia in 1987. He found a huge vertebra – as big as a person – which he mistakenly took for a piece of petrified wood. It wasn’t until 1993 that these bones were identified as coming from a dinosaur. The Argentinosaurus fossils are extremely rare and considered a national treasure of Argentina and therefore it is impossible to observe remains of this titanosaur elsewhere in the world. Argentina is one of the richest countries in the world for fossil discovery and hundreds of exotic species of dinosaurs are found there.

To this day, the remains of Argentinosaurus are only fragmentary. No more than a dozen vertebrae, some ribs and a 5 feet long long femur were found. The skull is still missing, as is usually the case with these dinosaurs since the skull of titanosaurs was easily detached from the neck after their deaths. Argentinosaurus measurements are mainly based on estimates obtained by comparing fragmentary bones with those of close relatives known from complete skeletons.

Egg and development

Compared with the eggs of other titanosaurs, such as those of the eponymous Titanosaurus, it is possible that the Argentinosaurus eggs measured about 1 foot in diameter and that females laid between 10 and 15 eggs at a time which increased the chances that at least 1 newborn would escape predator attacks long enough to reach adulthood.

Time to maturity was, however, very long in cold-blooded herbivorous dinosaurs (at least that is presumed) such as sauropods and titanosaurs, unlike warm-blooded carnivorous theropods such as tyrannosaurs and raptors. A young Argentinosaurus could thus take 40 years before reaching its maximum size! This represents almost half of the life of these dinosaurs since it is known that the life expectancy of these animals could easily reach the century given their excessive corpulence, once they reached adulthood. This is a 25,000% increase in mass from hatch to herd's alpha leader.

Giganotosaurus prey

It is known that Argentinosaurus shared the same South American territory as the 10-ton carnivore Giganotosaurus since the remains of these two dinosaurs were found nearby. Although even a hungry Giganotosaurus had absolutely no chance against an adult-sized titanosaur – it's as if an 8-year-old was trying to attack a 500-pound mature man – Giganotosaurus may have been pack hunting in order to attack stragglers in nomadic herds of titanosaurs such as Argentinosaurus.

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