THE ADAPTATIVE RADIATION OF THE HYPSODONT THERIDOMYIDAE (RODENTIA) DURING THE LATE EOCENE

The aim of this paper is to analyze the first adaptive radiation of th e hypsodont theridomyid rodents during the Late Eocene from Western Eu rope. The study is based on new material from Aquitaine, Languedoc and Quercy. Five genera are considered in the study : Patriotheridomys, T heridomys, Blainvillimys, Pseudoltinomys and Elfomys and the different species are described. Among them, there are a new subspecies (Patrio theridomys altus neboulensis, from Sainte Neboule) and two new species (Blainvillimys civracensis, from Civrac and Elfomys hartenbergeri fro m Lascours). Their phyletic relationships are tentatively proposed, an d some evolutionary trends concerning these species can be drawn and t he stratigraphical and paleoecological implications are analyzed. We p ropose to define an intermediate standard level (MP 18a) between MP 18 (which become MP 18b), and MP 17. Their evolutionary modes are discus sed giving a new view on the first radiation of the hypsodont theridom yids. A global analysis of the change of the theridomyids diversity is presented.