| Summary: | In an attempt to disentangle the complex taxonomy of the <i>Labeobarbus</i> species of the Epulu River, a right bank headwater affluent of the Aruwimi, Central Congo basin, a morphological study was undertaken on 221 specimens from the Epulu and 32 type specimens. As a result, five different species have been distinguished, including four so-called rubberlips, <i>L. caudovittatus</i>, <i>L. macroceps</i>, <i>L. mawambiensis,</i> and <i>L.</i> sp. ‘thick lip’, and one chiselmouth, <i>L. longidorsalis</i>. While rubberlips have a curved mouth with well-developed lips and often a mental lobe, chiselmouths have a straight mouth with a keratinised cutting edge on the lower jaw. Among the specimens examined, several presented an intermediate mouth morphology between <i>L. mawambiensis</i> and <i>L. longidorsalis,</i> either with one or two pairs of barbels. One specimen exhibited an intermediate morphology between <i>L. mawambiensis</i> and <i>L. macroceps.</i> This morphological study, complemented with a molecular study of the mitochondrial gene cytochrome <i>b</i> (cyt <i>b</i>), suggests that these intermediates are probably hybrid specimens. The Epulu case is reminiscent to a case of possible hybridisation recently discovered in the Inkisi River (Lower Congo basin), but differs in having a lower relative abundance of hybrid specimens in the population, and in phylogenetic patterns.
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