The genus Astylosternus in the Upper Guinea rainforests, west africa, with the description of a new species (amphibia: Anura: Arthroleptidae)

Astylosternus laticephalus sp. nov. Rödel, Hillers, Leaché, Kouamé, Ofori-Boateng, Diaz & Sandberger is described from eastern Ivory Coast and western and central Ghana, and compared to Astylosternus occidentalis Parker, 1931 from the western part of the Upper Guinea forest zone (western Ivory Coast, Liberia, Guinea and Sierra Leone). Based on a comprehensive sample, including specimens from the entire range, the latter species is re-described. The new species is characterized by a body shape typical for frogs of the genus Astylosternus, but has an exceptionally broad head, i.e. broader than in A. occidentalis. The basic dorsal pattern of A. laticephalus sp. nov. consists of a brownish to brownish red colouration with distinct red dots (red dots are only rarely present in A. occidentalis). The new species has bicoloured eyes with the lower part of the iris being grey, the upper third of the iris is orange to red (A. occidentalis always has a uniform greyish iris). Males of the new species lack spines on the throat, belly (always present in A. occidentalis males), and a layer of black nuptial skin in the pectoral region (present in male A. occidentalis from western Guinea). Astylosternus laticephalus sp. nov. differs from A. occidentalis by a mean pairwise genetic distance of 3.2% in the investigated part of the mitochondrial 16S rRNA gene. Genetic divergence to the morphologically most similar Central African species, A. diadematus, was 11.9%. We briefly discuss the phylogenetic position of West African Astylosternus, hint on the possibility that the genus might be paraphyletic and discuss the biogeography of West African Astylosternus, in particular with respect to forest cover fluctuations in the past. Copyright © 2012.