Impact of the EECO on mammalian faunas: New Ypresian localities from Montpellier (France), a multidisciplinary approach

An integrative chronological study on a new terrestrial sedimentary sequence north of Montpellier (southern France) yields an age ranging from 52.1 to 49.7 Ma. This sequence contains three new mammalian fossil localities, for the first time described in this study, and is associated with the nearby specifically rich site of Mas de Gimel (MP10 — European Mammalian Paleogene Reference Scale [MP]). This study constrains the age of the Grauvian ELMA [European Land Mammal Age] with respect to the geological time scale, suggesting that it is more contemporary with the EECO (Early Eocene Climatic Optimum) than previously considered, and in particular with the period of High Amplitude Climate Fluctuations. These new faunas and data allow us to discuss the relevance of the European Mammalian Paleogene Reference Scale [MP] and to propose new continental biozones for the late Ypresian. It also demonstrates that the late Neustrian fauna (MP8 + 9) is contemporary with the onset of the EECO and that there may be several late- and post-EECO faunas in southern France. Our study moreover suggests phases of diversification during the warm periods, and extinction during the cooling, as observed in North America. Future refined dating of the European fossil localities of this key period will help to discuss the impact of global warming on mammalian communities in the frame of further intercontinental comparisons.