The Petrocephalus (Pisces, Osteoglossomorpha, Mormyridae) of Gabon, Central Africa, with the description of a new species

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.