Résumé
Defined mainly by dental features, the Paleogene genus Gliravus Stehlin and Schaub appears heterogeneous on the basis of the structure of the infra-orbital and masseteric region. The type-species G. majori Stehlin and Schaub (Quercy undet.), and a new species G. itardiensis described from Itardies (Quercy, new collections) have a protrogomorphous skull. The species G. prisais Stehlin and Schaub, allocated to a new genus Glamys, is characterized by a "myomorphous"; skull (from Mas de Got, Quercy, new collections). That two types of skulls, allied by a very similar dental pattern, coexisted since at least the beginning of the Middle Oligocene and probably since the Upper Eocene, proves on the one hand that this "myomorphy"; probably derives from a primitive protrogomorphy; it is a pseudo-myomorphy by comparison with the myomorphy of the Cricetidae, which has arisen from hystricomorphous ancestors. On the other hand, it shows that these glirids evolved at different rates, the Glamys lineage being the more progressive.