June 6, 2012
New Technique Shaves Tons Off Dinosaur Weight
Dinosaurs, some of the largest creatures to have ever walked the earth, have for the first time been accurately weighed by scientists using a new technique, and the results indicate that we have been guilty of wrongly portraying them as massively heavy beasts.
Biologists at the University of Manchester, using lasers to calculate body mass, measured the minimum amount of skin that would be required to contain the skeletal structure of modern-day mammals, including reindeer, polar bears, and elephants. Producing a formula based on those calculations, the scientists then used the lasers to map out the amount of skin that dinosaurs would need to contain their skeleton.
In particular, the experts tested a Brachiosaur skeleton at Berlin´s Museum of Natural History (Museum fur Naturkunde). They estimated that the specimen, long believed to have weighed as much as 80 tons, actually weighed closer to 23 tons.
Publishing their findings in the journal Biology Letters, the team said their calculations would apply to all dinosaur weight measurements, possibly making all dinosaurs lighter than previously believed.
“One of the most important things paleobiologists need to know about fossilized animals is how much they weighed,” said lead author Dr. Bill Sellers in a prepared statement. “This is surprisingly difficult.”
However, when using the new laser technique to measure several modern mammals, calculating the minimum wrapping volume of the main skeletal sections, the results “demonstrated that it consistently underestimated body mass by 21 percent,” he explained, adding the calculations helped them to determine the accurate weight of the Berlin Brachiosaur, Giraffatitan brancai.
He further explained that body mass was a critical parameter 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,” he added.
“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,” he said.
Mike Taylor of University of Bristol, told Discover Magazine that there are potential issues with making an accurate weight measurement. He has estimated the weight of Giraffatitan before and believes about 70 percent of its volume comes from the torso. He noted that reconstructing the torso is rather difficult for large dinosaurs, because the ribs are often distorted or poorly preserved. He also said that using a single density value isn´t that appropriate for brachiosaurs.
Taylor did note, however, there were several benefits of the laser technique. “It requires no irreproducible judgments on the part of the person using it, and it´s ground-truthed on solid data from extant animals.” And, it´s also fully automated.
If it truly works for dinosaurs, we can weigh these extinct beasts as quickly as the laser-scanner can be wheeled around a museum, added Taylor. “It´s an important new method which I expect to see widely adopted.”
“Our method provides a much more accurate measure and shows dinosaurs, while still huge, are not as big as previously thought,” Sellers concluded.