New data on the mammalian fauna from the late middle Eocene (MP 15-16) of Mazaterón (Soria, Spain): The youngest presence of the genus Prodissopsalis (Hyaenodonta, Hyaenodontidae) in Europe.

The Hyaenodonta were the most diverse carnivorous mammals in the European Eocene and were classically divided into three subfamilies: Sinopaninae, Arfianinae, and Proviverrinae, with this latter being the most successful of the three, as it exhibited a much larger geographic and temporal range. This classification is currently abandoned, as cladistic analyses of Hyaenodonta showed that several of these groups were paraphyletic. In any case, the former "proviverrines" were European endemic hyaenodontids which occupied the niche of small to medium-sized predators from the Ypresian (MP7) to the Priabonian (MP19). Recent phylogenetic proposals recognize the "Eurotherium clade" including this latter genus, besides Cartierodon and Prodissopsalis. A single species is known for Prodissopsalis, Prodissopsalis eocaenicus, previously recorded in European fossil sites of MP 12 to MP 14; nevertheless, the new material studied here, a mandible of a subadult individual from the late Middle Eocene (Bartonian, MP 15-16) site of La Solana (Mazaterón, Soria, Spain) constitutes a new species of Prodissopsalis and the youngest record of this genus up to now, extending its chronological range and remarking the shelter role of the northwestern region of the Iberian Peninsula during the Middle and Late Eocene. The new species, Prodissopsalis jimenezi provides new data not only on the eruption sequence of the genus, but also on the evolution of its dental adaptations, as the new species exhibits a more trenchant, hypercarnivorous dentition in comparison to the more primitive species P. eocaenicus, which would point toward a refining of the hunting abilities of this hyaenodont during the Middle Eocene.