Supermassive dinosaur found in Argentina: Meet Dreadnoughtus

A giant sauropod dinosaur found in Argentina is the largest land animal ever discovered for which a body mass can accurately be calculated.

Rendering of Dreadnoughtus schrani. Mark A. Klingler, Carnegie Museum of Natural History

Paleontologists find new dinosaurs fairly regularly, but not on this scale: a new supermassive dinosaur species has been discovered in Argentina that is calculated to have tipped the scales at a whopping 59.3 metric tonnes -- that is, 59,300kg or 130,734 pounds -- and measuring a massive 26m from nose to tail.

Moreover, the skeleton of the Titanosaur -- a Late Cretaceous herbivore given the name Dreadnoughtus schrani, excavated over a period from 2005 to 2009 -- is unusually complete, with over 70 percent of the bones represented. It is this that has allowed a team of researchers to accurately calculate the weight of the giant beast -- the biggest land animal for which this has been possible.

"Dreadnoughtus schrani was astoundingly huge," said Kenneth Lacovara, PhD, an associate professor in Drexel University's College of Arts and Sciences, who discovered the Dreadnoughtus fossil skeleton in southern Patagonia in Argentina and led the excavation and analysis.

"It weighed as much as a dozen African elephants or more than seven T. rex. Shockingly, skeletal evidence shows that when this 65-ton 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."

Titanosauriansauropod dinosaurs, common during the Late Cretaceous (66-100 million years ago) are some of the largest animals ever to walk the Earth, but nearly all of them are only known from incomplete fossils. Their sizes are only estimated from a limited number of bones.

Kenneth Lacovara with the right tibia of Dreadnoughtus schrani. Kenneth Lacovara

Typically, the size of a dinosaur can most accurately be gauged by using measurements taken from the femur (thigh bone) and humerus (upper forelimb). The skeleton discovered by Lacovara's team included over 100 elements, including all of the vertebrae from the 30ft (9.14m) tail, a neck vertebra with a diameter over 1 yard (91.44cm), scapula, ribs, toes, a claw, a section of jaw and a single tooth, and nearly all the bones from the animals limbs -- allowing for a "gold standard" weight estimate.

Prior to the discovery of Dreadnoughtus schrani, the largest confirmed dinosaur was the Elaltitan, also hailing from Patagonia, coming in at 47 tons. It is possible, the researchers said, that Argentinosaurus was bigger, but because the skeleton discovered was incomplete, lacking bones from its forelimbs, its size cannot be accurately gauged. Futalognkosaurus, also from Patagonia, may also be comparable, but the most complete specimen ever found was still lacking most limb bones.

"Titanosaurs are a remarkable group of dinosaurs, with species ranging from the weight of a cow to the weight of a sperm whale or more," said Carnegie Museum of Natural History's Matthew Lamanna, PhD, who also worked on the dig. "But the biggest titanosaurs have remained a mystery, because, in almost all cases, their fossils are very incomplete."

Lacovara et al

Dreadnoughtus schrani was named because Lacovara believed it would have had little to fear.

"With a body the size of a house, the weight of a herd of elephants, and a weaponised tail, Dreadnoughtus would have feared nothing. That evokes to me a class of turn-of-the-last century battleships called the dreadnoughts, which were huge, thickly clad and virtually impervious," he said. "I think it's time the herbivores get their due for being the toughest creatures in an environment."

Species name "schrani" was chosen to honour entrepreneur Adam Schran, who provided support for the research.

Overall, the find represents 45.3 percent of the dinosaur's skeleton, or 70.4 percent of the types of bones in its body, excluding the head bones. In order to better visualise the skeleton, the team 3D scanned all the bones from both Dreadnoughtus schrani and Futalognkosaurus -- previously the most complete titanosaur ever found -- and built a 3D reconstruction, publicly available for download in the paper's supplementary materials.

The full paper, "A Gigantic, Exceptionally Complete Titanosaurian Sauropod Dinosaur from Southern Patagonia, Argentina", can be read online in the journal Scientific Reports.