Knowing an extinct animal's mass is crucial for estimating its physiological traits but the standard technique — in which a model of the animal is made and its mass then calculated from its density — has been criticized for being too subjective.
Bill Sellers at the University of Manchester, UK, and his team laser-scanned the skeletons of 14 large mammals, including the bison and the elephant. The researchers used the scans to mathematically derive 'convex hulls' of the bones — the minimum volume that encloses a set of points, akin to gift-wrapping a teapot — and converted these volumes into estimates of mass. These were then compared to the known values.
The method consistently underestimated true body mass by 21%. Thus, using this method and then adding 21% should provide more accurate predictions. When the team used the corrected technique on Giraffatitan brancai, one of the largest dinosaur skeletons in the world, the beast clocked in at 23,200 kilograms, similar to recent volumetric estimates.
Biol. Lett. http://dx.doi.org/10.1098/rsbl.2012.0263 (2012)