The locality Cavalé (Quercy, France) has yielded a rich fossil mammalian fauna, in which Theridomyidae (Rodentia) and Cainotheriidae (Artiodactyla) are the most abundant. Thirty five mammal species are documented, with eight rodent species (Blainvillimys gregarius, Atavocricetodon aff. nanus, Sciuromys cayluxi, Pseudoltimys major, Issiodoromys medius, Gliravus tenuis, Paleosciurus goti and Lophallomys atavus n. comb.). The study of two rodent families is particularly developed. First are the Theridomyidae, of which the abundance allows a subtle analysis of their evolutionary modes. On the contrary, the Aplodontidae are documented by a unique upper molar, but it allows to define a new genus for the species atavus. The analysis of the theridomyine Blainvillimys gregarius Schlosser, 1884 population, compared to that of other lower Oligocene localities (Mas de Got and La Plante 2, for MP22, and Pech Crabit for MP23, Quercy) lead to a revised systematics of this lineage, with a better definition of its evolutionary characters. The whole evolutionary changes within the lineage, and not only the increase of hypsodonty, are morpho-functionally interpreted as an adaptation to a more abrasive diet, related to the relatively arid environments of the early Oligocene. The arguments provided by the occurrence of Blainvillimys gregarius and other mammal species allow to assess the datation of the locality close to the mammal Paleogene standard level MP22, in the lower Oligocene.