Dreadnoughtus May Lose its Title as 'World's Heaviest Dinosaur'

Dreadnoughtus - the long-necked herbivore recently uncovered in Patagonia - was previously thought to be the world's heaviest dinosaur, but now new findings may upend its heavyweight title.

Nature World News reported back in September of an unknown dinosaur called Dreadnoughtus schrani, hailing from the Late Cretaceous Era about 77 million years ago. Clocking in at roughly 65 tons, it seemed clear that this might have been the largest dinosaur ever to walk the Earth.

However, a new study published in the journal Biology Letters says that this behemoth actually weighed between 30 and 40 tons - considerably less than originally thought.

"Estimating the body mass of an extinct animal from approximately 77 million years ago of this size from only its fossilized bones is extremely challenging and relies on the availability of certain data from living animals and modeling techniques," the study's lead author, Karl Bates, a lecturer of musculoskeletal biology at the UK's University of Liverpool, said in a statement.

"Using digital modeling and a dataset that took in species, alive and dead, we were able to see that the creature couldn't be as large as originally estimated."

But some scientists, including Kenneth Lacovara, the paleontologist who discovered the dinosaur, are not convinced. The model in the new study uses the dinosaur's body volume as a proxy for its mass. Even though this is the most complete skeleton ever found of a dinosaur of this size, scientists still have only about 45 percent of Dreadnoughtus' skeleton, Live Science reports.

"They're using a proxy that doesn't exist to estimate a number that can never be validated," Lacovara told Live Science.

Found in Patagonia, the huge fossil had almost all of the major bones intact, allowing scientists to confidently estimate its overall size - measuring in at 26 meters (85 feet) long.

Whereas Lacovara's team used a well-known scaling equation to determine Dreadnoughtus' body mass, the latest study used a 3D skeletal modeling method to paint a more accurate picture.

The fact that two other uncovered sauropods, with similar proportions to Dreadnoughtus, weighed much less than the bruiser tipped researchers off that something was amiss. Their technique is unique in that it relied on a mathematical model to reconstruct the volume of the dinosaur's skin, muscles, fat and other tissues around the bones.

"The original method used to calculate the mass of the animal is a common one and has been used successfully on many specimens," Bates said in the statement. "The highest estimates produced for this particular giant, however, didn't quite match up."

It is still unclear which group of researchers has it right, pending further study, but if its heavyweight title is eventually retracted, then all dino weight estimates will be called into question.

Even so, the fact remains that Dreadnoughtus was enormous.

"One thing we can all agree on is that these giant dinosaurs were among the heaviest land animals ever to walk the Earth," Matthew T. Mossbrucker, director and chief curator of the Morrison Natural History Museum, who wasn't involved in either study, told The Washington Post. "Surely Dreadnaughtus pushed the limits of terrestrial animal mass."

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