Taxonomy & naming
Petrocephalus petersi was described in 2012 by Bernd Kramer, Roger Bills, Paul Skelton and Michael Wink, one of five new species named in their critical revision of the churchill snoutfish genus Petrocephalus across southern and eastern Africa, published in the Journal of Natural History. The species belongs to the family Mormyridae within the order Osteoglossiformes, the bonytongues — an ancient teleost lineage named for a bony, toothed structure on the tongue that bites against toothed plates on the roof of the mouth. No synonyms are documented, and the name has stood as described.
The type locality is a stream near campsite 1 at the edge of the wet Zambezi River System in Mozambique (18°33'54"S, 35°39'46"E). The genus name Petrocephalus is built from the Greek petros (rock, stone) and kephale (head), referring to the hard, blunt cranium shared across the genus. The species epithet honors Wilhelm Peters (1815–1883), the German zoologist and explorer who led the first major fish survey of the lower Zambezi region between 1842 and 1848; the original description does not spell out the dedication in more detail than the name itself.
Morphology
Petrocephalus petersi is a small fish, reaching about 3 in standard length according to FishBase — near the small end of a genus that already runs small. The body is fusiform and round-oval in cross-section, with body depth running 28.7–32.3% of standard length. The head is broadly rounded, and the mouth is small, subterminal and set low, positioned ventral to the eye rather than at the tip of the snout — the underslung feeding posture typical of Petrocephalus and distinct from the elongated chin appendage of its relative Gnathonemus. The dorsal fin carries 18–20 soft rays and the anal fin 25–26, with no spines in either fin.
As in all mormyrids, an electric organ near the base of the tail generates a weak, pulsed electric field that the fish reads through electroreceptors spread across its skin, using the resulting signal to navigate and locate food in dim or turbid water. No electric organ discharge waveform has been published specifically for Petrocephalus petersi. Species in the genus generally emit triphasic discharges that differ enough between species to serve as a more reliable identification tool than external appearance, but that generalization has not been confirmed for this species with recorded data.
Habitat
Petrocephalus petersi is known from Mozambique, recorded from the Zambezi River Delta and the nearby Melela River. The type locality is a medium-sized, strictly freshwater stream at the edge of the wet Zambezi River System, with a substrate of sand carrying substantial leaf litter and marginal grass along the banks — a tropical, low-lying lowland habitat.
The species is demersal, living and foraging near the stream bottom rather than in open water. Beyond the type locality description, no further habitat detail — water chemistry, seasonal flow patterns, or additional collection sites — has been published for this species.
Feeding
No specific diet has been documented for Petrocephalus petersi. FishBase estimates a trophic level of 3.2 ± 0.4 for the species, derived from its closest relatives rather than from direct dietary study, which places it in the same general benthic-invertebrate-feeding niche as the rest of the genus — small mormyrids typically locate insect larvae, worms and tiny crustaceans hidden in sand and leaf litter using their electric sense, then take them with a quick strike of the small downturned mouth.
Mating
No mating or courtship behavior has been recorded for Petrocephalus petersi. Mormyrids in general are thought to use their species-specific electric organ discharge in courtship and in recognizing the sex and identity of other fish, but this has not been studied or confirmed for this species specifically.
Breeding
Breeding is unrecorded for this species — no wild or captive spawning account has been published for Petrocephalus petersi. Breeding biology in Petrocephalus generally is poorly known, and nothing about egg-laying, parental care, or spawning triggers can be stated for this species without extrapolating well beyond what the literature actually reports.
In the aquarium
Petrocephalus petersi has no documented presence in the aquarium trade; described only in 2012 from a limited Mozambican river system, it is essentially unknown outside the taxonomic literature. Nothing about its behavior or requirements in captivity has been recorded.
If a specimen were ever kept, general mormyrid husbandry would apply: a soft sand substrate for probing, dim lighting, ample cover, stable and clean water, and live or frozen invertebrate foods such as bloodworm, since mormyrids as a group tend to ignore dried foods and are notably sensitive to poor water quality and to some medications. None of this has been tested against this particular species, and it should not be read as an established care record.
Conservation
Petrocephalus petersi has not been evaluated by the IUCN Red List. FishBase lists a low fisheries vulnerability index (10 of 100), a measure of susceptibility to fishing pressure rather than a conservation assessment, and no species-specific threats have been documented.
The species is known only from the Zambezi River Delta and the Melela River in Mozambique, a narrow recorded range that reflects limited survey effort in the region as much as any confirmed rarity. Without a formal Red List assessment, its conservation status should be treated as genuinely unknown rather than assumed safe.