New fossils of Amphicyonidae (Carnivora) from the middle Miocene (MN6) site of Carpetana (Madrid, Spain)

Abstract

Herein, we present a study of an interesting sample of fossils of the giant amphicyonid Megamphicyon giganteus (Schinz, 1825) from the Spanish middle Miocene (MN6) site of Carpetana (Madrid city), obtained during public works for the Madrid underground in 2008. Although the dentition of this species is known from other sites, the postcranial bones are very poorly known, and the new material provides new data on the locomotor adaptations of this spectacular predator, and allows an estimation of its body mass, which would be around 600 kg. Surprisingly, despite this giant size, the morphology of both femur and tibia shows that this animal exhibited higher cursorial capacity than large extant carnivorans, such as bears, which together with a high degree of pronation/supination movement of the forearm, reveals adaptations of M. giganteus to occupy the niche of active top predator in middle Miocene ecosystems. RÉSUMÉ Nouveaux fossiles d'Amphicyonidae (Carnivora) du Miocène moyen (MN6) de Carpetana (Madrid, Espagne). Nous présentons ici l'étude d'un échantillon intéressant de fossiles de l'amphicyonidé géant Megamphicyon giganteus (Schinz, 1825) du gisement espagnol du Miocène moyen (MN6) de Carpetana (Madrid), obtenus lors de travaux publics dans le métro de la ville en 2008. Bien que la dentition de cette espèce soit connue sur d'autres sites, les os postcrâniens sont très mal connus, et le nouveau matériel fournit de nouvelles données sur les adaptations locomotrices de ce spectaculaire prédateur, et permet une estimation de sa masse corporelle, qui avoisinerait 600 kg. Étonnamment, malgré cette taille gigantesque, la morphologie du fémur et du tibia montre que cet animal présentait des capacités de coureur plus élevées que les grands carnivores existants, tels que les ours, ce qui, outre un degré élevé de mouvements de pronation/supination sur l'avant-bras, révèle les adaptations de M. giganteus à occuper le créneau des principaux prédateurs actifs des écosystèmes du Miocène moyen.

Caught in travertine: computed tomography reveals the youngest record of Amphicyon giganteus from the travertine deposits of Karacalar (late middle Miocene, central Anatolia, Turkey)

“…Kuss ( 1965 ) erected the genus Megamphicyon for the species giganteus , separating it from Amphicyon on the basis of size and details in the dentition. This generic distinction was not recognised by subsequent authors (e.g., Morales et al 2003 ; Peigné et al 2006b ; Morlo et al 2019a , b ), but, recently, Siliceo et al ( 2020 ) reinstated the genus Megamphicyon . As we noted above, the differences in dental morphology between Amphicyon giganteus and A. major are very small.…”

“…2 2019 Amphicyon giganteus Morlo, Miller, Bastl, Abdelgawad, Hamdan, El-Barkooky and Nagel ( 2019a ), p. 739, fig. 4 2020 Megamphicyon giganteus Siliceo, Morales, Antón and Salesa ( 2020 ), pp. 225, 227–232, figs.…”

“…Recently, material of Amphicyon giganteus was described from the MN6 locality of Carpetana, Spain (Siliceo et al 2020 ). The material agrees with the Karacalar specimen for the morphology of the premolars are the diastemata between p2–p4, the p3 and p4 with distal accessory cuspids and large p4.…”

“…As we noted above, the differences in dental morphology between Amphicyon giganteus and A. major are very small. Siliceo et al ( 2020 ), who included well-preserved postcranial elements in their study, state in their introduction that there “are enough morphological differences to support a generic separation”. However, in their descriptions and conclusions, they stress the similarity with A. major .…”

“…Because of the overlap in both geographic and stratigraphic ranges between Amphicyon major and A. giganteus , Siliceo et al ( 2020 ) suggested that the two amphicyonids should have occupied different niches and may even have lived in different ecosystems. Their body mass estimates of ∼ 150 kg for A. major and ∼ 600 kg for A. giganteus certainly suggest that the latter was capable of handling larger prey.…”