First occurrence of Ischyrictis zibethoides (Carnivora, Mustelidae, Guloninae) from the Middle Miocene of Southwestern Europe

This study describes the cranial remains of Ischyrictis zibethoides from the Middle Miocene of La Retama (MN5, Spain) and Ischyrictis bezianensis from the Early Miocene of Baigneaux (MN4, France). The presence of I. zibethoides in La Retama represents the first record of this species in the Iberian Peninsula, previously known exclusively from France and Germany. Additionally, we suggest that I. cf. bezianensis from Quinta de Farinheira (MN5, Portugal) should be reclassified as I. cf. zibethoides. Ischyrictis zibethoides from the localities of Sandelzhausen (MN5, Germany) and Sansan (MN6, France) exhibits significant variability in size and dental morphology, particularly in the first molars (M1/m1). The diversity of large-sized mustelids (over 10 kg) is a noteworthy feature of the carnivoran associations during the Middle Miocene in Europe. They almost exclusively occupied the mesocarnivore niche, which in North American faunas was shared by large mustelids and canids. The decline in diversity of large-sized mustelids coincided with the rise in size and diversity of hyaenid species, which was detected in European faunas towards the end of the Middle Miocene.