Just Big-Boned? Dinosaurs Skinnier Than Once Thought, Scientists Say

Do these sauropod fossils make me look fat?

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Reuters / Frank Polich

This 40-foot tall brachiosaurus is sporting a conspicuously baggy Chicago Bears jersey, proudly showing of his new, slender figure.

According to a new study by researchers at the University of Manchester, we owe the dinosaurs an apology.

Traditional methods of deducing the weight of a dinosaur have been drastic overestimations, the scientists say — in some cases by tens of thousands of pounds.

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To come up with their new numbers, the researchers analyzed the size and weights of existing large animals such as polar bears and elephants, using lasers to measure the amount of skin wrapped around their skeletons. By comparing the animals’ average weights with the minimum possible amount of skin necessary to cover their skeletons, they discovered that these creatures have around 21% more body mass than the minimum “skin and bone” wrap size. They could then use this ratio to estimate an average weight for dinosaurs based on the ‘wrap size’ of their skeletons.

To tets their hypothesis the researchers tried it out on a Brachiosaurus, a massive sauropod from the Jurassic era, whose skeleton resides in a Berlin museum. The technique resulted in reducing the dinosaur’s weight to 25 tons, down from estimates that ranged from 35 to 88 tons previously.

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In an interview with Discovery News, William Sellers, the lead author of the study, called the Brachiosaurus’ weight estimate “quite low” but added that “it reflects the fact that all dinosaur weights are getting lower” —  the estimated size of dinosaurs has been diminishing with each new scientific study of the subject since the 1960s.

Some serious paleontological liposuction will be needed in natural history museums if the new research sticks, as the previous method of calculating dinosaurs’ body size — building artistic reconstructions of their bodies based on fossils and then estimating their water displacement — is discredited.

According to Sellers, these artistic reconstructions were notoriously unreliable: “No two people would get exactly the same answers. Some would make them fat dinosaurs, and some would reconstruct them as skinny dinosaurs.” The whole point, he notes, was to “get around the guesswork.”

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