Body mass estimate of Anancus arvernensis (Croizet and Jobert 1828): comparison of the regression and volumetric methods

Abstract

In this contribution, we estimate the possible living body mass (BM) of the anancine gomphotheriid Anancus arvernensis, by testing a recently proposed volumetric method based on hyper-realistic in vivo 3D reconstructions and comparing the results with the BM obtained by using regression formulas. The analysis, conducted starting from two articulated skeletons, showed that the performance of regression formulas varies considerably from taxon to taxon, with plausible estimates obtained only when the mean of all the formulas on the individual bones is available and considered. Differently, formulas applied to single bones can lead to underestimations or overestimations of up to 300%, with BM ranging from 54 kg to 26 metric tonnes. By using the volumetric method, the in vivo reconstruction of Anancus arvernensis made it possible to estimate a BM between 5.2 and 6 t, a figure close to that of an extant adult male African elephant. The obtained results show that estimating BM in terrestrial tetrapods from single or fragmented bones might lead to highly improbable and misleading conclusions. Thus, in the presence of adequately complete mounted skeletons, it is always preferable and recommended to estimate the BM using the volumetric approach, which is based on an in vivo 3D reconstruction.