Taxonomy & naming
Petrocephalus pellegrini was described by the Belgian ichthyologist Max Poll in 1941, in a paper titled "Poissons nouveaux de la Côte d'Ivoire" (new fishes of the Ivory Coast), published in the Revue de Zoologie et de Botanique Africaines (volume 34, issue 2, pages 133–143). It belongs to the family Mormyridae within the order Osteoglossiformes, the bonytongues, and its type locality lies in coastal river basins of Côte d'Ivoire. No synonyms are documented for the name.
Poll distinguished the new species from the widespread and superficially similar Petrocephalus bovei by a smaller eye and a shorter anal-fin base — the kind of fine-grained, overlapping character that makes field identification within Petrocephalus notoriously unreliable, and that later revisions of the genus have increasingly replaced with electric organ discharge waveforms as the more dependable diagnostic tool.
Morphology
Petrocephalus pellegrini reaches about 3.5 in standard length, small even by the standards of a genus made up entirely of small fish. FishBase records 19 to 26 soft rays in the dorsal fin and 26 to 31 in the anal fin, with no spines in either fin, and describes the body coloration as uniformly brown, without the banding or reflective patterning seen in some other Petrocephalus. Like its relatives it has the round-snouted, compressed head and small, underslung mouth typical of the genus, quite unlike the elongated chin appendage of the related Gnathonemus elephantnoses.
As in every mormyrid, an electric organ in the caudal peduncle generates a weak, pulsed electric field that the fish reads through electroreceptors across its skin. No electric organ discharge has been recorded specifically for Petrocephalus pellegrini. Broader surveys of Petrocephalus species in the Upper Volta river system have documented triphasic, species-specific discharge waveforms across the genus, underscoring how central this signal is to distinguishing look-alike species, but that work has not been extended to P. pellegrini itself.
Habitat
Petrocephalus pellegrini is a freshwater, bottom-associated fish native to a scatter of coastal and Niger-tributary drainages in Upper Guinea, West Africa. It is recorded from coastal river basins between Sierra Leone and Côte d'Ivoire, including the Sassandra River system; from the Niandan River, a tributary of the Niger in Guinea; and from the upper Cavally River. This distribution spans several separate basins rather than one continuous range.
Specific temperature, pH, and substrate data have not been published for this species. Upper Guinea's coastal rivers run warm year-round and undergo strong seasonal flow changes tied to the West African monsoon, but that is a general expectation for the region rather than a measurement taken for P. pellegrini itself.
Feeding
Published dietary information is limited to a FishBase-derived trophic level of 3.2, placing Petrocephalus pellegrini as a lower-level carnivore or omnivore in line with the rest of the genus. No specific prey items have been documented. Other Petrocephalus locate small benthic invertebrates — insect larvae, worms, and tiny crustaceans — by electrolocation in mud and leaf litter, and this species is presumed to feed the same way, though that has not been confirmed for it directly. There is no aquarium feeding record to draw on, since the species has no established history in the trade.
Mating
No mating behavior has been described for Petrocephalus pellegrini. In mormyrids generally, the electric organ discharge is thought to carry information used in courtship and in recognizing the sex and identity of other individuals, alongside its role in navigation, but this has been studied closely in only a handful of species and P. pellegrini is not among them. Whether it shoals, pairs, or shows any reproductive signalling behavior is unrecorded in the available literature.
Breeding
No spawning account exists for Petrocephalus pellegrini, in the wild or in an aquarium. As with the great majority of Petrocephalus species, nothing has been published on egg deposition, incubation, or parental care for this fish, and none of that should be assumed from better-studied relatives without direct evidence.
In the aquarium
Petrocephalus pellegrini has no established presence in the aquarium hobby and no documented import or captive-keeping history, unlike the handful of Petrocephalus and Gnathonemus species that do reach the trade occasionally. If it were ever kept, general mormyrid husbandry practice would apply: soft sand for probing, subdued lighting, ample cover, and stable, low-turbidity water — mormyrids as a group are unusually sensitive to poor water quality and to many common aquarium medications, particularly those containing copper.
At around 3.5 in the species would not need a large tank, but nothing about its temperament, tankmate compatibility, or social requirements in captivity has been recorded. Any aquarium guidance for this species is currently extrapolation from the wider genus, not direct experience with it.
Conservation
The IUCN Red List assesses Petrocephalus pellegrini as Least Concern, based on a 2019 assessment. No major species-specific threats are documented. Its range across several separate West African coastal and Niger-tributary drainages — including the Sassandra system, the Niandan River, and the upper Cavally River — supports the current designation, though populations across Upper Guinea's small river systems are not closely monitored, and regional pressures such as deforestation and agricultural runoff remain a general long-term concern rather than a documented driver of decline in this species specifically.