One of the heftiest dinosaurs that strode the Earth may have weighed as much as six buses less than thought, according to a new formula that will also place other dinosaurs in a lower weight class. The Berlin Brachiosaur was previously estimated to weigh as much as 80 tonnes.

But a new calculation of its mass, published by scientists recently, suggests it would have tipped the scales at a relatively featherweight 23 tonnes.

“Our results would suggest that many of the previous estimates (for all dinosaurs) are indeed too heavy,” study author Bill Sellers told AFP.

For most dinosaurs, the discrepancy would not be as big as that for the Brachiosaurus, “but certainly we would suggest that lighter estimates are likely to be correct.”

The team of biologists used 14 large-framed modern mammals to devise a new method of estimating body mass using only the skeleton.

“It's a mathematical technique that effectively wraps a skin as tightly as it can around the bones,” explained Sellers of the University of Manchester. “This gives us a ‘skin and bones' model (from) which we can measure the volume.” The study revealed that the weight of modern-day animals was 21 per cent more than the so-called “wrapping volume” — which equation was then applied to the dinosaur bones.

More In: Sci-Tech