Comparative anatomy of the shoulder region in the Late Miocene Amphicyonid magericyon anceps (Carnivora): Functional and paleoecological inferences

Abstract

We describe and discuss several aspects of the functional anatomy of the shoulder of the Miocene amphicyonid Magericyon anceps, focusing on the scapula and proximal half of the humerus. This species, only known from the late Miocene (Vallesian, MN 10) site of Batallones-1 (Madrid, Spain), is the last amphicyonid known in the fossil record of Western Europe. Magericyon anceps combines a more hypercarnivorous dentition than previous amphicyonids (including relatively more flattened canines) with primitive features on its shoulder region: its scapulo-humeral region shows a reduced caudoventral projection of the acromion, the postscapular fossa, and the teres major process, suggesting some differentiation from the two morphotypes exhibited by other derived amphicyonids, and showing similarities with primitive, generalized, medium-sized species of this family. This unique combination of a derived dentition and a relatively generalized shoulder region points towards M. anceps being a different ecological morphotype from that showed by other amphicyonids such as the larger, bear-like amphicyonines from the European middle Miocene and the markedly cursorial North American temnocyonines and daphoenines.