August 31, 2009

How heavy was the biggest dinosaur?

Recent research suggests dinosaurs may not have been as heavy as previously thought. Two statistical methods for estimating body mass were compared. One method uses a log transformation for analysis and the result is then transformed back to arithmetical measure. This method usually produced overestimates when applied to mammals with known body mass. The other method uses non-linear regression, and produced notably more accurate estimates of body mass when applied to the same mammalian data set. The more accurate method was applied to dinosaurs, with the result that estimates of dinosaur body mass were considerably lower than previous estimates. The discrepancy was proportionally greater in larger than in smaller dinosaurs. The largest dinosaur in the study, Apatosaurus was estimated to have a body mass of 18,000 kg, which is roughly half the previous estimates of 38,000 and 35,000 kg. Even so, this is more than twice the 7,500 kg weight of an African elephant. Of course, one should keep in mind that it is not possible to confirm the calculated weight of dinosaurs, since there are none around to weigh!

Source: G.C. Packard, T.J. Boardman and G.F. Birchard. Allometric equations for predicting body mass of dinosaurs. Journal of Zoology 279:102-110. (2009)