When paleontologist Kenneth Lacovara of Drexel University in Philadelphia first uncovered the bones of the creature Dreadnoughtus, from the rocky plains of Patagonia back in 2005, scientists agreed it was big. It was initially estimated to weigh around 65 tons and stretch 85 feet in length when it roamed the planet over 75 million years ago. But new research indicates revisions may be in order, for perhaps the behemoth wasn't quite so huge.

"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," says study co-author Dr. Karl Bates, a biology lecturer at the University of Liverpool in England. "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."

The new research utilized 3D modeling to reproduce the dinosaur's skeleton in order to estimate the volume and density of its bones and soft tissue. Using data from living animals, the revisions placed the dinosaur's weight at between 30 and 40 tons, about half the original estimate.

"Our analysis suggests that only the lower estimates produced by previous methods are plausible," Bates says. "Estimates of 60 tons and above do not fit with our current understanding of the mass characteristics of living land animals."

But Dr. Lacovara disagrees. He claims that since the new research used the dinosaur's body volume as a proxy for its mass, the new estimate is flawed, since the actual volume of the creature's body is unknown. Less than half its skeleton was recovered, making volume estimates difficult to calculate.

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

So the dino debate continues. But one thing's for sure: Whether it weighed 40 tons or 60, it was one giant dinosaur.

The new research was published online June 10 in the Royal Society journal, Biology Letters.