Exploring dietary adaptations in Ursus minimus: a 3D geometric morphometric analysis of the mandible

Abstract

The extinct bear Ursus minimus, which lived in Europe during the Pliocene and possibly Early Pleistocene, is considered the common ancestor of all modern Ursini. U. minimus is thought to have been omnivorous, with a preference for invertebrates. The present study aims to investigate its potential adaptations to this diet using 3D geometric morphometrics. Landmarks for 3D digitization of the mandible were selected to represent functional morphology. Extant and extinct Quaternary Ursidae were digitized as a comparative reference sample, followed by generalized Procrustes superimposition, with the data subsequently corrected for allometry through a pooled regression analysis. Principal component analysis was performed on the regression residuals and a phylogeny mapped onto the morphospace. The present study reveals that the mandibular morphology of U. minimus aligns more closely with omnivorous species than with insectivorous bears, challenging the idea of its insectivorous tendencies. As the common ancestor of modern Ursini, U. minimus' omnivorous dietary flexibility implies that U. minimus possessed a generalized adaptive strategy, which could have served as the foundation from which more specialized dietary forms later evolved.