Just How Big Was the Largest Dinosaur? Bigger Than You Think.

Reaching nearly half a football field in length and starting from an egg smaller than a human baby, this dinosaur was king of herbivores.

The largest dinosaur that ever lived has been revised many times. Some paleontologists thought it was the Brontosaurus, way back in the day. Since then, the coveted crown of the world’s largest dinosaur has shifted a few times. Regardless, the type of dinosaur that must have been the largest animal to ever walk the face of the earth has never been in question. It was a type of sauropod.


Sauropods were a type of dinosaur that appeared in the late Jurassic period which were characterized by large, columnar legs, very long necks and tails, small heads and were herbivores. Their long necks were useful for plucking vegetation from the tops of prehistoric trees, much like a modern giraffe would do today, only much taller.

The word “sauropod” actually means lizard-feet in Greek. Because of their enormous weight, they had to balance all of their weight on four very sturdy legs. We now believe their tail was used to counterbalance the weight of their neck and head since tails seem to be relatively proportional in mass to the neck head area, when that varied among individual species.


As noted above, the very first sauropods appeared in the late Jurassic period. However, through the Triassic period, their prevalence grew and by the Cretaceous period, they could be found nearly anywhere in the world. The combination of sheer mass and ability to harvest nutrients from forest canopies helped keep them mostly immune to attacks by smaller, predatory species. By the late Cretaceous period, sauropods had developed to such an enormous size that we now refer to them as Titanosauria.

Reconstruction of Argentinosaurus — Image by Nobu Tamura

Argentinosaurus, as its name implies, was found in Argentina, specifically in the Northern region of Neuquen. It was identified by legendary paleontologist José Bonaparte. At first, only a few vertebrae were found but, just from those few bones, it was very clear that Argentinosaurus would be among the largest dinosaurs ever found. In fact, the farmer who originally discovered the vertebrae on his property thought that they were actually petrified logs.

Argentinosaurus vertebrae next to paleontologist Matt J. Wedel — Image by Matt J. Wedel

How big was it?

After finding more evidence, scientists discovered that Sauropods, including Argentinosaurus, were actually very small at birth. In fact, an Argentinosaurus egg only had about 1 liter of volume, about the size of a large water bottle, much smaller than a human baby. However, the dinosaur was able to grow extremely rapidly.

A full grown Argentinosaurus stretched over 100 ft long, with some estimates putting it at 130ft long. However, compared with other sauropods, Argentinosaurus was much heavier. It is now considered to have been the largest land animal that ever lived in terms of mass, and possibly length as well. Scientists believe that an adult Argentinosaurus could reach up to 100 tons. To put that in perspective, a modern elephant can only reach about 7 tons in weight, so an Argentinosaurus actually weighed more than 13 elephants.

The End of Giants

Artist depiction of the “dinosaur killer”

Argentinosaurus, like all other non-bird dinosaurs, was wiped out in the infamous K-T extinction event when a comet or asteroid impacted the Yucatan peninsula at the end of the Cretaceous period (around 66 million years ago), wiping out three quarters of all species on earth. At the time of the impact, based on recovered fossil evidence, sauropods like Argentinosaurus had become so successful in adapting to different environments that their bones have been found on all seven continents, including Antarctica. Due to the catastrophic change in climate, mammals and birds were favored by natural selection, thus paving the way for the rise of humans far in the future.

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