On the occurrence and distribution of Synodontis nigrita and S. violaceus (Siluriformes: Mochokidae) in the Nilo-Sudan, and Upper and Lower Guinea ichthyofaunal provinces.

Examination of the holotype of Synodontis nigrita, the type specimens of both its (potential) junior synonyms, S. fascipinna and S. ornatus, plus an additional 306 specimens, previously identified as S. nigrita, confirmed that the interorbital width is the most important diagnostic character to distinguish S. nigrita from its Nilo-Sudanic, and Upper and Lower Guinea ichthyofaunal province congeners. Results revealed that this species has a typical N-S distribution. Additionally, the occurrence of Synodontis violaceus in the Cross River is not corroborated. Therefore, it should be considered a typical West African species.