Episemion Radda & Puerzl

Rainer Sonnenberg, Thomas Blum & Bernhard Y. Misof, 2006, Description of a new Episemion species (Cyprinodontiformes: Nothobranchiidae) from northern Gabon and southeastern Equatorial Guinea., Zootaxa 1361, pp. 1-20 : 2

[[ Genus Episemion Radda & Puerzl ]]

The currently monotypic genus Episemion was erected by Radda & Pürzl (1987a) with the description of Episemion callipteron Radda & Puerzl, 1987 , a then newly discovered species from the northern inland plateau of Gabon. The genus appears to have no close affinities to any other African Nothobranchiidae. Its phylogenetic placement is still uncertain, and two different hypotheses are currently under debate. Some authors place Episemion within, or close to, the genus Epiplatys Gill, 1862 (Nothobranchiidae: Epiplateinae), categorized as a subgenus without any supporting characters except for a very general similarity in color pattern and body outline (Radda & Pürzl, 1987a,b; Neumann, 2000). Other authors have placed it, more convincingly, within the Nothobranchiinae and close to Aphyosemion Myers, 1924 , based on a number of morphological characters, including the frontal and preopercular neuromast system (van der Zee, 2002; Wildekamp, 1996). Although it seems highly probable that Episemion is a genus in the large Aphyosemion (sensu lato) complex , its relationship to other groups remains unclear. Van der Zee (2002) and Huber (1998a) assumed a relationship to a group composed of Chromaphyosemion Radda, 1971 , Diapteron Huber & Seegers, 1977 and Kathetys Huber, 1977 . A closer affinity to Epiplatys is highly unlikely following the study of van der Zee (2002).

At this time only a small number of additional Episemion localities from Gabon and Equatorial Guinea are known, aside from the type locality (Map 1). Populations from northern parts of the Monts de Cristal in Gabon and in adjacent parts of southeastern Equatorial Guinea differ in color pattern from the typical Episemion callipteron . During a study of the cyprinodontiform fishes of northern Gabon, we were able to collect specimens of this genus in the Monts de Cristal region. Data presented here are mainly based on these collections and on additional material from Equatorial Guinea provided by M. Juhl, as well as a specimen from an aquarium strain originating from the first collection at the type locality of Ep. callipteron (GWW 86/20). This material has allowed us to test the taxonomic status of the aberrant populations using mitochondrial DNA data and to make first assumptions on the systematic position of this genus.