The factors that limit the distribution of the highly diverse lemur fauna of Madagascar are still debated. We visited an understudied region of eastern Madagascar, a lowland rainforest site (Sahafina, 29-230 m a.s.l.) close to the Mantadia National Park, in order to conduct a survey and collect further distributional data on mouse lemurs. We captured, measured, photographed, and sampled mouse lemurs from the Sahafina forest, performed standard phylogenetic methods based on three mitochondrial DNA genes, and conducted morphometric comparisons in order to clarify their phylogenetic position and taxonomic status. The mouse lemurs from the Sahafina forest could not be assigned to any of the known mouse lemur species and were highly divergent in all molecular analyses from all previously described species. Since they also differed morphometrically from their sister species and from their geographic neighbors, we propose species status and include a species description at the end. This study suggests that M. lehilahytsara may be the first highland specialist among all mouse lemurs. The distribution of the newly described mouse lemur is not fully known, but seems to be rather restricted and highly fragmented, which raises serious conservation concerns.
While several morphometric analyses in lemurids have focused on the craniofacial complex, the characterization of their mandibular morphology has received less attention. The mandibular outline, in lateral perspective, was quantified using elliptical Fourier analysis, in an osteological sample encompassing 189 lemurid mandibles (66 Eulemur, 51 Hapalemur, 22 Lemur and 50 Varecia), and compared using multivariate statistical techniques. The taxonomic value of this outline in Lemuridae was demonstrated by the existence of significant separations between the four genera studied. In particular, the mandibular morphology of Hapalemur was markedly different from that in the group Eulemur-Lemur-Varecia. Excluding Hapalemur from analysis, the distinctions between Eulemur, Lemur and Varecia were enhanced suggesting the existence of more subtle intergeneric differences in mandibular morphology. Variation in mandibular form was greatest in Hapalemur and smallest in Eulemur and Varecia (as demonstrated by the mean values of interindividual distances); variation was higher in Lemur than in Eulemur and Varecia, but not higher than in Hapalemur. This morphological diversity may be related to functional adaptation in response to particular dietary habits. The patterns of intergeneric and intrageneric shape variations of the mandible in Lemuridae presented here provide a valuable resource for the analysis of variation among living and fossil lemurids.
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