June 6th, 2012 by James Ayre
Using a new technique to more accurately estimate the weights of some dinosaurs, researchers have found that some dinosaurs were not nearly as heavy as previously thought.
Biologists from the University of Manchester used lasers to measure the minimum amount of skin necessary to wrap around the skeletons of modern-day animals such as polar bears, elephants, reindeers, and giraffes. They found that the animals had exactly 21% more body mass than the minimum skeleton ‘skin and bone’ wrap volume. They then applied this to a giant Brachiosaur skeleton in Berlin’s Museum für Naturkunde.
The previous estimates of this Brachiosaur’s weight have been as high as 80 tons, but the new research reduces that estimate down to 23 tons, making for a much lighter, leaner, animal.
“One of the most important things palaeobiologists need to know about fossilised animals is how much they weighed. This is surprisingly difficult, so we have been testing a new approach. We laser scanned various large mammal skeletons, including polar bear, giraffe and elephant, and calculated the minimum wrapping volume of the main skeletal sections,” lead author Dr Bill Sellers is quoted as saying.
“We showed that the actual volume is reliably 21% more than this value, so we then laser scanned the Berlin Brachiosaur, Giraffatitan brancai, calculating the skin and bone wrapping volume and added 21%. We found that the giant herbivore weighed 23 tonnes, supporting the view that these animals were much lighter than traditionally thought.”
Body mass is one of the critical parameters used to “constrain biomechanical and physiological traits of organisms.”
“Volumetric methods are becoming more common as techniques for estimating the body masses of fossil vertebrates but they are often accused of excessive subjective input when estimating the thickness of missing soft tissue.”
“Here, we demonstrate an alternative approach where a minimum convex hull is derived mathematically from the point cloud generated by laser-scanning mounted skeletons. This has the advantage of requiring minimal user intervention and is therefore more objective and far quicker.”
“We tested this method on 14 large-bodied mammalian skeletons and demonstrated that it consistently underestimated body mass by 21%. We suggest that this is a robust method of estimating body mass where a mounted skeletal reconstruction is available and demonstrate its usage to predict the body mass of one of the largest, relatively complete sauropod dinosaurs, Giraffatitan brancai, as 23,200 kg.”
“The value we got for Giraffatitan is at the low range of previous estimates; although it is still huge, some of the enormous estimates of the past — 80 tonnes in 1962 — are exaggerated. Our method provides a much more accurate measure and shows dinosaurs, while still huge, are not as big as previously thought.”
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