On the identity of the West African killifish Aphyosemion maeseni Poll, 1941 (Cyprinodontiformes : Aplocheilidae)

Populations of the West African killifish, traditionally identified as Aphyosemion maeseni Poll, 1941, have been classified for the last four decades in the tribe Callopanchacini. However, in a recent study, populations of this widespread species have been placed in a new genus and species, Nimbapanchax leucopterygius, while the unique holotype that Poll used to describe Aphyosemion maeseni has been referred to the genus Epiplatys. Comparison of 3D reconstruction images of the holotype of A. maeseni with cleared and stained specimens of several African Aplocheiloid taxa revealed that: the morphology of the epineural ribs and the neural processes of vertebrae 5-7 are typical of Callopanchacines and not like those of Epiplatys. Furthermore, the neural process of the second vertebra is fan-shaped, which is a synapomorphic characteristic of the recently described genus, Nimbapanchax. As the morphology of the holotype of A. maeseni and that of examined specimens of N. leucopterygius prove highly concordant and we are unable to record any morphological characteristic that would diagnose each as a member of a distinct taxon, we propose N. leucopterygius to be a junior synonym of A. maeseni. A species synonymy and re-diagnosis of Aphyosemion maeseni Poll, 1941 is provided.