Taxonomy & naming
Otopharynx sp. "Flat Jaw" has no describing author, no publication date, and no entry under a validated name in Eschmeyer's Catalog of Fishes; it is an informal field/trade name, not a scientific one. The genus Otopharynx (Regan, 1920) is diagnosed chiefly by features of the pharyngeal jaw and by a melanic pattern of discrete flank blotches, and several of its species and undescribed forms are named for a distinctive mouth or jaw shape adapted to a particular way of taking prey. "Flat Jaw" is used as a field descriptor for more than one undescribed Otopharynx population around the lake, including a blue-coloured form recorded at Kadango; no published study has established whether the Senga Bay population and these other "flat-jaw" forms represent a single species or several independently evolved, similarly jawed lineages. It should be treated as a distinct, unresolved entity pending formal study.
Morphology
As its trade name records, this form is distinguished chiefly by a flattened, underslung lower jaw, distinct from the more generalised, moderately oblique mouth typical of most Otopharynx. A flattened jaw of this kind, in Malawi cichlids generally, is usually associated with picking prey close along a flat surface — sand, rock, or the lakebed itself — rather than seizing prey in open water. Beyond this documented cue, no formal morphometric study has been published for this population. The body should be expected to follow the moderately deep, laterally compressed shape typical of the genus, with genus-typical size for a mid-sized Otopharynx running to roughly 4.5–6 in total length. Females are expected to be plainer than breeding males, in keeping with the wider haplochromine pattern of the lake.
Habitat
The form is recorded from Senga Bay, a well-known and heavily visited locality near Salima on the central-western shore of Lake Malawi, popular with both tourists and cichlid collectors and documented as home to several Otopharynx forms. Otopharynx species generally occupy the sand-rock interface or open sand rather than dense rocky reef, foraging at moderate depths, and a flat-jawed feeding style points toward close association with a firm, flat substrate — sand or exposed rock — rather than crevice-dwelling. The surrounding water is warm, hard and alkaline, consistent with Lake Malawi's littoral zone throughout, though the precise depth range used by this specific form has not been documented.
Feeding
The "flat-jaw" trade name points to a feeding style built around a flattened lower jaw suited to picking prey directly off a flat surface — sand or rock — rather than the more generalised biting or sifting strategies of other Otopharynx. The precise diet has not been documented by a formal stomach-content study, but the jaw shape suggests a benthic invertivore taking small invertebrates from close along the substrate. This account should be read as inference from the trade name and general Otopharynx biology rather than a directly documented finding.
Mating
Breeding behaviour has not been documented specifically for this form. By analogy with other Otopharynx and the wider Lake Malawi haplochromine assemblage, males in breeding colour are expected to hold a territory on sand or rock and display to attract passing females, following the general haplochromine courtship pattern built around egg-spot markings on the male's anal fin. No locality-specific field account of courtship exists for the Senga Bay population.
Breeding
As in all Lake Malawi haplochromines, reproduction is by maternal mouthbrooding: the female carries the fertilised eggs and subsequent fry in her mouth, without normal feeding, for several weeks until they are ready for independent release, with the male taking no further role after spawning. Clutch size and brooding duration have not been documented for this specific form; genus-typical figures for mid-sized Otopharynx suggest a modest clutch and a brooding period of several weeks.
In the aquarium
Otopharynx sp. "Flat Jaw" is an uncommon fish in the hobby, generally reaching keepers through specialist Malawi cichlid importers working the accessible Senga Bay area rather than general retail. A tank for it should provide a sand substrate along with moderate rockwork, reflecting its likely sand-rock interface habitat, and open swimming space. Water chemistry should follow the Lake Malawi standard — hard and alkaline, pH roughly 7.7 to 8.6, temperature 75–82 °F. Otopharynx species are generally less aggressive than rock-dwelling mbuna and are usually kept successfully alongside other calm, similarly sized Malawi haplochromines. Diet should include a quality cichlid pellet supplemented with small live or frozen invertebrates such as bloodworm and brine shrimp.
Conservation
Otopharynx sp. "Flat Jaw" has not been evaluated by the IUCN and, as an undescribed form, has no Red List status of any kind. Its documented range is a single locality, Senga Bay, on the accessible and heavily visited central-western shore of Lake Malawi, but no population assessment or targeted study has been published for this specific form. In the absence of that data, the honest position is that it is unassessed, and that a form known from a single locality warrants the same general caution applied to other narrow-range Malawi endemics.