Built for Strength: Functional Insights from the Thoracolumbar and Sacrocaudal Regions of the Late Miocene Amphicyonid Magericyon anceps (Carnivora, Amphicyonidae) from Batallones-1 (Madrid, Spain)

Abstract

We describe and discuss the morphology and functional anatomy of the thoracolumbar and sacrocaudal regions of the vertebral column of the late Miocene amphicyonid Magericyon anceps. These regions are essential for body support, and very relevant for locomotion and prey capture, and thus their study provides interesting insights on the paleobiology and biomechanics of this top predator. Magericyon anceps, the last known amphicyonid in the fossil record of Western Europe, is recorded only from the Vallesian sites of Batallones-1 and Batallones-3 (Madrid, Spain), which have yielded hundreds of fossils of this species, constituting one of the best-known samples of an amphicyonid ever recorded. The morphology of the thoracolumbar region of M. anceps shows some interesting features, such as a characteristic anticlinal region and a powerful and remarkably rigid lumbar region. This suggests that the back of this carnivoran was built for supporting extremely strong tensions that could be generated during different activities, such as running, but these tensions would be more likely suffered when subduing prey during hunting. Also, M. anceps had a long muscular tail, which could be helpful in balancing of various body motions during these activities. In summary, all these features suggest that M. anceps was a powerful predator built for strength, supporting previous hypotheses about the adaptation of this carnivoran to fast killing of prey inhabiting relatively well-vegetated habitats.