Taxonomic revision of mouse lemurs (Microcebus) in the western portions of Madagascar

The genus Microcebus (mouse lemurs) are the smallest extant primates. Until recently, they were considered to comprise two different species: Microcebus murinus, confined largely to dry forests on the western portion of Madagascar, and M. rufus, occurring in humid forest formations of eastern Madagascar. Specimens and recent field observations document rufous individuals in the west. However, the current taxonomy is entangled due to a lack of comparative material to quantify intrapopulation and intraspecific morphological variation. On the basis of recently collected specimens of Microcebus from 12 localities in portions of western Madagascar, from Ankarana in the north to Beza Mahafaly in the south, we present a revision using external, cranial, and dental characters. We recognize seven species of Microcebus from western Madagascar. We name and describe 3 spp., resurrect a previously synonymized species, and amend diagnoses for Microcebus murinus (J. F. Miller, 1777), M. myoxinus Peters, 1852, and M. ravelobensis Zimmermann et al., 1998.