Described overnight in Scientific Reports, the long-necked dinosaur has been classified as an entirely new genus and species, Dreadnoughtus schrani - a name fitting its impressive size.
The researchers report that Dreadnoughtus weighed almost 60 tonnes, was two storeys tall at the shoulder, and measured a massive 26-metres long long from nose to tail. The fossil was discovered in the southern Patagonia region of Argentina in 2005, and it's the largest fossil mass of a single organism ever uncovered.
"It weighed as much as a dozen African elephants or more than seven T. rex. Shockingly, skeletal evidence shows that when this [specimen] died, it was not yet full grown. It is by far the best example we have of any of the most giant creatures to ever walk the planet,” Kenneth Lacovara, an associate professor at Drexel University, in California, who discovered the fossil, said in a press release.
Dreadnoughtus appears to have lived in the late Cretaceous Periods (around 77 million years ago) in high-altitude and forested valleys, and is part of a group of large herbivores known as titanosaurs. Despite the size of titanosaurs, scientists still know very little about them, and this is the largest fossil ever found of one of the giant species.
"For the [largest] dinosaurs, which we call titanosaurs, finding anything around 20 percent of the fossil is usually considered a home run," Lacovara told William Herkewitz, a journalist for Popular Mechanics. "Normally you only find a handful of bones, and the previous record was a 27 percent complete skeleton. With Dreadnoughtus we found 70 percent."
Dreadnoughtus's fossils are so huge that it took four annual trips to get them all out of the ground, and another four years of cleaning and prep before the specimen could be studied.
For scale, here is Lacovara photographed against the right tibia (shin bone) of Dreadnoughtus.
The reason it’s usually so hard to find almost-complete fossils of large dinosaurs is because fossilisation requires an animal to be buried quickly in sediment - something that’s quite tricky for an animal the size of a building.
But Lacovara believes that a rapid pair of floods, caused by broken earthen levees in the valley where Dreadnoughtus was found, resulted in the quick fossilisation of the species. Sedimentary records from the area support this find, Popular Mechanics reports.
It’s likely Dreadnoughtus may be the largest animal to ever lived on land, but it’s a complicated claim as other contenders, such as Argentinosaurus, are only known from a handful of fossils, so scientists have only been able to roughly estimate their size.
But for now, this is the largest land animal we’ve been able to properly calculate the size of. And the researchers are using the incredibly detailed fossil record, which includes evidence of muscle attachment sites, to build computer models to explain how dinosaurs moved.
“As you understand these creatures' locomotion and ability to move around, you can start answering questions about feeding, their place in the ecosystem, and a whole number of other avenues of research," co-author Jason C. Poole from Drexel University told Popular Mechanics.
Find out more about the discovery in the video below, and, if you're really keen, check out the detailed 3D scans of the fossils that the researchers have made freely available.