Analysis of mammalian communities from the late Eocene and Oligocene of southern France

Serge Legendre

Valverde's cenogram method is used to analyse mammalian communities from the late Eocene to late Oligocene of southern France, mainly from the "Phosphorites du Quercy". Cenogram analysis involves plotting the size of each component species in a fauna on a semilog diagram in rank order, permitting fossil faunas to be compared with Recent ones. The configurations of Recent communities serve as models for establishing the general environmental characteristics of fossil mammalian faunas. This method of analysis applied to faunal sequence can reveal major and sudden ecological perturbations. The paleobiogeographical event (i.e. the mammalian immigration wave) at the Eocene-Oligocene Boundary in western Europe, known as the «Grande Coupure", is here shown to represent a drastic and sudden ecological change: late Eocene tropical environments in Europe deteriorated rapidly turning to subdesert or desert environments al the beginning of the Oligoccne.