In this paper, we study variation in the morphology and electric organ discharges (EODs) of Petrocephalus Marcusen, 1854 (Pisces, Osteoglossomorpha, Mormyridae) collected in Gabon, Central Africa. We recognize four valid species: P. simus Sauvage, 1879, P. balayi Sauvage, 1883 (= Mormyrus amblystoma Günther, 1896), P. microphthalmus Pellegrin, 1908, and P. sullivani n. sp. Petrocephalus sullivani n. sp. differs from all others by the following combination of characters: lack of black spot at the base of the dorsal fin; more than 18 branched rays on the dorsal fin; more than 14 scales (rarely 14) between the origin of the anal fin and the lateral line; inferior mouth with the distance from the anterior extremity of the snout to the mouth between 2.7 and 4.4 times in head length (average 3.2); and EOD duration 216 ± 29 microseconds, with prominent third phase (P3). We summarize the geographical distribution of each species and provide a key to species of the genus Petrocephalus from Gabon based on diagnostic characteristics from external morphology.
Pisces, Mormyridae, electric fishes, EOD, Gabon, Africa, Petrocephalus sullivani n. sp., new species.