Résumé
This paper provides a detailed description and the functional anatomy of the forelimb of an early Oligocene genet-sized arctoid carnivoran, Amphicynodon leptorhynchus, to infer its probable lifestyle. This work represents the first insights into the functional anatomy of the postcranial skeleton and palaeoecology of an emblematic member of the first radiation of arctoid carnivorans, the poorly known Amphicynodontidae, a group very likely related to bears. So far, the Amphicynodontidae have only been studied on the basis of their cranial and dental remains. The fossil site of Itardies (MP23, lower Oligocene), in the Quercy Phosphorites (France), have yielded hundreds of postcranial remains attributed to Am. leptorhynchus, allowing a complete analysis of its locomotor behaviour in comparison to a large sample of extant carnivorans showing diverse lifestyles. The anatomy of the forelimb of Am. leptorhynchus indicates well-developed climbing skills and grasping abilities. Thus, this early arctoid was probably living mostly in trees, moving on the ground basically for foraging as observed in small modern climbing carnivorans such as the red panda or the kinkajou, although some other climbing carnivorans can also live in rocky areas.