Finite element and morphological analysis in extant mammals’ claws and quaternary sloths’ ungual phalanges

Abstract

ABSTRACT As the ungual phalanges of tetrapods are the first structures that interact with the substrate, studying them is of great importance when wanting to know the locomotor behaviour of different species. In this work, we analyse the ungual phalanges of the third finger from the manus of several Pleistocene sloths: G. robustum, L. armatus, M. jeffersonii, M. americanum, S. leptocephalum; and of a wide range of extant xenarthrans and other mammals. The third finger of the manus was chosen because of its larger size and nearly perfect bilateral symmetry, which enhances the possibility to observe functional differences between taxa. The analysis performed on them were of the inner and external curvature and the finite element method. By comparing the results obtained for the fossils and the extant species we were able to indicate possible habits for these Pleistocene ground sloths. Through these analyses the three mylodontid sloths: G. robustum, L. armatus and S. leptocephalum showed a preference for strenuous activities such as digging. On the contrary, M. jeffersonii and M. americanum, although they showed similar resistant structures, they learned more towards a less specific locomotor habit, such as generalised terrestrial mammals.