Nouvelles espèces subfossiles de rongeurs du Nord-Ouest de Madagascar

Since the mid-19^th century, the Malagasy subfossil macrofauna has been the object of numerous studies and publications, contrary to the microfauna. New fieldwork, initiated in 2001, in the North West of Madagascar (Province of Mahajanga) led to the discovery of sites rich in fossiliferous breccias, containing micromammals. In this article, we describe two new subfossil species of rodent: Brachytarsomys mahajambaensis, the smallest within the genus and Nesomys narindaensis, the largest within the genus. Most of the extant species of these two genera live in the tropical rainforests of the eastern and north-eastern areas of Madagascar, far away from the north-western part of the island where a dry deciduous forest occurs. The presence of the two taxa in the subfossil record in the Northwest of the country suggests the occurrence of wetter conditions in the past in this region.