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Introduction
Many localities in Europe show high species richnesses in mammals during the Paleogene (Biochrom’97 1997). One of the main climatic events, the Eocene–Oligocene cooling (ca. 33.9 Mya), was a global shift from greenhouse to icehouse climate, concurrent with a major faunal upheaval for a large part of the mammalian clades present in Europe at that time (e.g., Legendre et al., 1991; Weppe et al., 2023). This event, called the ‘Grande Coupure’, signals environmental changes of great magnitude characterized by an increased aridity and the development of open habitats such as savannahs or steppes at the expense of closed habitats such as forests (Legendre, 1987; Legendre & Hartenberger, 1992). These environmental modifications are the main cause of the extinction of endemic species, as first noted by Stelhin (1909), and also drove a massive immigration from Asia (Legendre & Hartenberger, 1992), as recently emphasized in artiodactyls (Weppe et al., 2023). This faunal turnover occurred between MP20 and MP21 reference levels (Legendre et al., 1991), and more precisely between 34.1 and 33.55 Mya, according to Weppe et al. (2023)
At the core of the trophic interactions induced by this great mammalian diversification, two clades of predatory mammals stand out: Hyaenodonta and Carnivoramorpha (Solé et al., 2011, 2014, 2016, 2022a). These carnivorous mammals represent an informative example of the faunal disruption characteristic of the ‘Grande Coupure’. Hyaenodonts are abundant and much more diverse in the Eocene (56 Ma to 33.9 Ma) than carnivoramorphans, whereas the crown clade Carnivora (Wesley-Hunt & Flynn, 2005), dominate considerably from the Oligocene onwards (33.9 Ma to 23.03 Ma) (Solé et al., 2022a). While the vast majority of carnivorans appear and diversify during the Oligocene, only one clade originates and shows diversity during the Eocene in Europe: Amphicyonidae.
Amphicyonidae or “bear-dogs”—so colloquially called because of their anatomical resemblances with both canids and ursids—are dated, for the oldest occurrences, from the Bartonian (Duchesnean North American Land Mammal ‘age’) of North America (Tomiya & Tseng, 2016). With more than 34 genera (Mckenna & Bell, 1997), and a stratigraphic distribution ranging from the Middle Eocene to the Late Miocene (Goswami & Friscia, 2010), the phylogenetic position of amphicyonids is much unresolved (Viranta, 1996). Initially considered as closely related to Canidae (Matthew & Granger,...