A new method to calculate allometric length-mass relationships of dinosaurs

Body mass is an important determinant of most biological functions, and kno wing the mass of extinct animals is essential in order to learn about their biology. It was the aim of this paper to develop a method of mass estimati on which would make it possible to determine allometric length-mass relatio nships for the different groups of dinosaurs. Mass is calculated from graph ical reconstructions of fossils, or from photos of skeletal mounts or live animals. Body shape of animals is described by high order polynomial equati ons, integration of the polynomial gives body mass of a 'round' animal, whi ch is then corrected for animal width by intersection with a second equatio n (Y = 1 - ax(2)). The method was validated by predicting body mass of exta nt animals of known mass and with complex body shapes (kangaroos, emu, elep hant, giraffe, rhinoceros). Body mass increased allometrically with total l ength in all groups of dinosaurs (Ankylosauria, Ceratopsia, Ornithopoda, Pr osauropoda, Sauropoda, Stegosauria and Theropoda), but 95% confidence inter vals were very large for Ankylosauria and Stegosauria so that, for those gr oups, the resulting regression equations have little predicting power. Scal ing exponents were least for the Sauropoda which may have grown less massiv e to function at their great body size. Scaling exponents were greatest for the Theropoda, but it was speculated that small coelurosaurs, as the precu rsors of birds, may have grown less massive compared to other theropods. Ma ss estimated by the 'polynomial' method presented here did not differ signi ficantly from mass estimates in the literature where these were available.