A systematic revision of the large-scaled Marcusenius with description of a new species from Cameroon (Teleostei; Osteoglossomorpha; Mormyridae)

Nine out of 37 recognized species in the genus Marcusenius have eight large circumpeduncular scales rather than 12 or 16, which is more typical of the genus. They are: M. dundoensis, M. fuscus, M. ghesquierei, M. intermedius, M. kutuensis, M. lambouri, M. moorii, M. paucisquamatus and M. schilthuisiae. All nine are restricted to West-Central and Central Africa. A detailed morphometric analysis could not distinguish differences between M. moorii, M. paucisquamatus and M. lambouri. Therefore they are considered as synonyms with M. morrii as the senior synonym. The systematic status of M. intermedius is uncertain owing to the existence of only three specimens. Within this species complex a new species, Marcusenius sanagaensis, is described from the Sanaga River basin in Cameroon. It differs from all the others in the number of scales on the lateral line and in the extent of the broad dark band between the anterior base of the dorsal fin and the anterior base of the anal fin. All valid Marcusenius species with eight circumpeduncular scales are redescribed and a key to these species is given.