Taxonomy & naming
Petrocephalus squalostoma was described by the Belgian-British zoologist George Albert Boulenger in 1915. It is placed in the family Mormyridae — the elephantnoses and mormyrids — within the order Osteoglossiformes, the bonytongue fishes, one of the most ancient surviving lineages of teleosts, named for a bony, toothed structure on the tongue that bites against toothed plates on the roof of the mouth. The genus Petrocephalus was erected by Marcusen in 1854 and now holds several dozen small African mormyrids, several of them described only in the last two decades through revisions built around electric organ discharge rather than external shape alone.
The parenthetical form of the authority — (Boulenger, 1915) — is the standard nomenclatural signal that the species was originally placed in a genus other than Petrocephalus before a later worker moved it; the original combination and the paper that reassigned it are not identified in the sources reviewed for this account. Boulenger described a long run of small Central African mormyrids in this period, several collected during Belgian Congo expeditions of the early twentieth century, but nothing available here ties Petrocephalus squalostoma to a specific river system or type locality, and none should be assumed.
Morphology
No measurements, meristic counts, or diagnostic description have been located for Petrocephalus squalostoma beyond its bare listing as a valid name, so no maximum length can be given with confidence. Other described Petrocephalus species range from under 2 in to roughly 8 in; where this species falls in that range is not documented in the sources reviewed.
Like other members of the genus, it presumably carries the compact, laterally compressed body, blunt rounded head, and small, downturned mouth typical of Petrocephalus, rather than the elongated chin appendage — the schnauzenorgan — that identifies the related genus Gnathonemus. As in all mormyrids, an electric organ near the base of the tail generates a weak, pulse-type discharge, read through electroreceptors spread across the skin and used to navigate and locate prey where eyesight is of limited use. Modern taxonomic work on the genus increasingly relies on the shape of this discharge, rather than external anatomy alone, to separate species that otherwise look alike; no discharge waveform has been published for Petrocephalus squalostoma.
Habitat
No habitat description, water-chemistry data, or confirmed locality has been published for Petrocephalus squalostoma in the sources reviewed for this account. FishBase and the Catalog of Fishes record it as a recognized name without elaborating on its ecology or range, and no country list or river-basin assignment could be confirmed.
Congeners in the genus typically occupy soft, still, or slow-moving tropical African fresh water — muddy backwaters, lagoons, and vegetated river margins, the low-visibility settings where an electric sense outperforms eyesight — but that is a family-level generalization rather than a documented fact for this species, and it should not be read as a description of where Petrocephalus squalostoma actually lives.
Feeding
Diet has not been directly studied for Petrocephalus squalostoma. Mormyrids generally forage over soft substrate for benthic invertebrates — insect larvae, worms, and small crustaceans — locating prey by electrolocation rather than sight, typically after dark. There is no reason from the wider genus to expect this species to differ, but that remains an inference rather than an observation of this particular fish.
Mating
Nothing has been published on courtship or mating behaviour in Petrocephalus squalostoma. In mormyrids generally, the electric organ discharge is thought to carry information relevant to mate choice — species identity, and in some studied populations sex — alongside its role in navigation, but the mechanics of how that translates into courtship have been worked out for only a handful of well-studied genus members.
Whether any of this applies to Petrocephalus squalostoma is unknown. No pairing behaviour, courtship display, or spawning-related activity has been recorded for the species, in the wild or otherwise.
Breeding
There is no published record of Petrocephalus squalostoma breeding, in the wild or in captivity. Breeding biology across Mormyridae as a whole is poorly documented and rarely achieved in aquaria even for well-studied genus members, and this species — with no confirmed distribution, no aquarium history, and almost no supporting literature — has no spawning account of any kind to draw on. A specific description of its reproductive mode would be invention rather than fact.
In the aquarium
Petrocephalus squalostoma has no documented presence in the aquarium trade. Unlike a handful of Petrocephalus species that occasionally reach hobbyists under a generic "elephantnose" or "churchill" label, nothing in the sources reviewed suggests this species has ever been imported, kept, or offered commercially.
Any care guidance would have to be extrapolated from the wider family rather than drawn from experience with this fish specifically. Mormyrids in general do best on a soft, fine substrate they can probe, in dimly lit tanks furnished with ample cover, and in stable, clean water — the group is notably sensitive to poor water quality and to a number of common aquarium medications, so cautious acclimation and conservative dosing matter more here than for most community fish. None of this has been tested against Petrocephalus squalostoma, and prospective keepers should not expect an established husbandry record for it.
Conservation
Petrocephalus squalostoma does not appear to have been formally assessed by the IUCN Red List; no status or assessment year could be confirmed in the sources reviewed for this account. Its range, population size, and any threats it might face are correspondingly unknown.
Many small, single-basin African mormyrids named during Boulenger's era have received little research attention since, and this species fits that pattern — a name that persists in the taxonomic record with essentially no accompanying ecological or conservation data. General pressures on Central African freshwater fish, such as habitat degradation, siltation, and increasing fishing effort, are the kind of long-term concern that could affect a poorly known species like this one, but there is no assessment evidence either way.