Marcusenius is a genus of African elephantfish in the family Mormyridae, part of the ancient bonytongue order Osteoglossiformes. The atlas covers 44 species ranging from 4.5 in up to 17.5 in, all sharing the mormyrid hallmark: a large brain-to-body ratio, a small mouth often set beneath a blunt or slightly protruding snout, and — most distinctively — a weak electric organ in the tail that generates a continuous, species-specific pulse used to navigate, find food, and communicate in dark or turbid water. Atlas records concentrate in tropical and southern Africa, with the Democratic Republic of the Congo, Angola, Cameroon, the Republic of the Congo, Ghana, Namibia, South Africa, and Côte d'Ivoire all represented, reflecting the genus's spread across major river systems from the Congo basin down to southern Africa.
Elephantfish have a devoted following among specialist aquarists, drawn to their intelligence, their electric sense, and their nocturnal, almost cat-like foraging along the substrate, though the group has a reputation for being demanding — Marcusenius species are notoriously sensitive to poor water quality and to common medications, and do best in soft, well-filtered, dimly lit tanks with sinking live or frozen foods. Most Marcusenius in the trade are wild-caught rather than farmed, since their weakly electric communication and social signalling make captive breeding difficult to replicate. Conservation status across the genus leans reassuring — 24 of the 44 species covered are assessed Least Concern — though a further 9 are Not Evaluated and a handful, including 2 Endangered and 3 Vulnerable species, face real localized pressure.