Foza raimundi, a new genus and species of potamonautid freshwater crab (Crustacea: Decapoda: Potamoidea) from northern Madagascar

—Foza raimundi, a new genus and species of freshwater crab from Antsiranana Province,northernMadagascar, isdescribedfromahigh-altitude locality in the isolated Marojejy mountain range. The unusual combination of characters of the new species warrants the establishment of a new genus to accommodate this taxon. The new taxon is compared to the other species of freshwater crabs occurring in Madagascar. The Malagasy freshwater crabs belong to the Potamonautidae, a family found exclusively in the Afrotropical zoogeographic region. The new taxon is endemic to Madagascar, as are the other six genera and 12 species of freshwater crabs found there. The most recent revision of the freshwater crabs of Madagascar (Cumberlidge & Sternberg 2002) recognized 12 species in six genera. The distribution of these endemic crustaceans was described in detail by Cumberlidge & Sternberg (2002) and by Cumberlidge et al. (2004); the latter authors also assessed the conservation status of each taxon. Of concern is the fact that ten Malagasy species were judged to be either threatened or extremely rare/endangered, and only two taxa (Hydrothelphusa agilis A. Milne-Edwards, 1872 and H. madagasacariensis (A. Milne-Edwards, 1872)) were considered to be secure (Cumberlidge et al. 2004). The high degree of endemism shown by the Malagasy freshwater crabs is a characteristic that they share with other terrestrial and freshwater organisms from this tropical island. These crabs are found in the lakes, streams, rivers, and adjacent terrestrial habitats throughout the island (Bott 1960, 1965: Ng & Takeda 1994; Cumberlidge 1999; Cumberlidge & Sternberg 2002, 2003; Cumberlidge et al. 2004); there are also a number of reports of their presence in phytotelmic habitats in rainforest ecosystems (Cumberlidge et al. 2002, Cumberlidge et al. 2005). We report here on the discovery of a new genus and species of freshwater crab from a high altitude locality in an isolated mountain range in northern Madagascar. The specimens described here are distinctly different from all known taxa in a number of important morphological taxonomic characters including those of the mandible, gonopods, carapace, sternum, epistome, chelipeds, walking legs, and third maxilliped. This unusual combination of characters is sufficient to warrant the recognition of a new monotypic genus to accommodate this species. Foza raimundi, new genus, new species, is compared to the other genera and species of freshwater crabs from Madagascar. The new taxon is assigned to the Potamonautidae sensu Cumberlidge (1999) and Cumberlidge & Sternberg (2002). Abbreviations.—Terminology is adapted from Cumberlidge (1999), and the * Corresponding author. PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 119(1):58–66. 2006.