Taxonomy & naming
The fish was named by the French ichthyologist Jacques Daget in 1954, in his monograph on the fishes of the upper Niger (Mémoires de l'Institut français d'Afrique Noire No. 36). Daget did not at first treat it as a full species: he described it as a Sudanian form of the coastal West African species Tylochromis jentinki (Steindachner, 1894), distinguishing the inland Niger-basin populations from their estuarine relatives. The type material came from Dioumanana, in the Cercle de Siguiri in north-eastern Guinea, on the upper Niger, with additional syntypes from the river system; the specimens are split between the Muséum national d'Histoire naturelle in Paris and the Natural History Museum in London. The genus Tylochromis itself had been erected by Charles Tate Regan in 1920, who combined the Greek tylos (a knob or callus) with chromis (an old name for a perch-like fish) in reference to the swollen bony apophysis on the underside of the skull and the thickened pharyngeal apparatus that characterise the group. The modern standing of sudanensis rests on Melanie Stiassny's comprehensive 1989 revision of the genus (Annales du Musée Royal de l'Afrique Centrale, 258), in which she designated a lectotype (MNHN 1924-0175), raised the form to full species rank, and re-diagnosed it among the roughly two dozen Tylochromis she recognised across West and Central Africa. Stiassny's later work (1990) placed the whole genus near the base of the African cichlid tree — an old, generalised lineage well outside the haplochromine and tilapiine assemblages — so sudanensis is best understood not as a recent specialist but as a long-established riverine survivor. It carries no widely used English common name; in the trade and the literature it is referred to by its scientific name.
Morphology
Tylochromis sudanensis is a heavy, laterally compressed cichlid with the large scales, steep forehead and small, low-set mouth that mark the genus as bottom-feeders rather than midwater hunters. Reported maximum size depends on how it is measured: FishBase lists 8 in standard length (snout to tail base), while a maximum total length of about 10 in has also been recorded — a solid, deep-bodied fish by riverine-cichlid standards but well short of the giant Lake Tanganyika congener Tylochromis polylepis. The fin counts run to 13–16 dorsal spines and 13–15 soft rays, three anal spines with seven or eight soft rays, and 28–29 vertebrae. Stiassny's diagnostic characters separate it cleanly from its relatives: thirteen or fewer (rarely fourteen) gill-rakers along the lower limb of the first arch, 37–43 lateral-line scales, a head length of roughly 28–34 per cent of standard length, and a relatively short pectoral fin that rarely reaches back to the level of the spinous anal fin. As in all Tylochromis, the two lateral lines and the robust lower pharyngeal jaw are key features; the pharyngeal mill is built for processing hard-shelled prey. Live colour is undramatic — a silvery to brassy-olive body over the large scales, paler below, in keeping with a turbid-water benthic forager rather than a reef show-fish. No marked, reliable sexual colour difference is documented for the species.
Habitat
This is a fish of the great Sudanian rivers of West and west-central Africa. FishBase gives its core range as the upper and middle Niger together with the Bénoué (Benue), Cross and Wouri rivers in Nigeria and Cameroon, and the IUCN assessment lists it from Cameroon, Chad, Guinea, Mali and Nigeria — a distribution that tracks the Nilo-Sudanian river basins rather than any single drainage. The type locality on the upper Niger in Guinea anchors the western edge of that range. These are warm, often turbid lowland waters: large, slow main-channel reaches, side-arms and the seasonally inundated floodplains that the West African monsoon fills each wet season, over soft sand and mud bottoms that suit a sifting feeder. As a benthopelagic species it works the bottom in shallow to moderate depths rather than open water; published precise depth bands are scarce for the species, but its floodplain-and-channel habit places it in the shallow benthic zone, on the order of the uppermost few metres. Water chemistry across the Sudanian zone is broadly warm and circumneutral to mildly alkaline — temperatures typically in the mid-20s to around 86 °F and pH near neutral to slightly basic — the regime its congeners share and the one it is kept at in captivity.
Feeding
Tylochromis sudanensis is a benthic omnivore that works soft sediment for food, with a trophic level estimated near 2.6 — low on the food web, the mark of a forager on plants and small invertebrates rather than a predator. FishBase, following Lamboj's account of the western African cichlids, records that it takes algae and plant matter as well as invertebrates. Mechanically it belongs to the genus's sand-sifting guild: it grubs through bottom sediment, and the robust lower pharyngeal jaw that defines Tylochromis lets the group crush hard-shelled prey such as snails and other molluscs. In sudanensis the pharyngeal apparatus is less extreme than in the most specialised snail-crushers of the genus (Tylochromis mylodon being the textbook durophage), which fits its more mixed, plant-and-invertebrate diet. In its river communities it functions as a generalist bottom forager of the soft-sediment and floodplain zones, processing detritus, vegetation and benthic invertebrates rather than competing as a specialist.
Mating
The reproductive biology of Tylochromis sudanensis follows the genus template, which is well documented even where this particular species' courtship has not been watched in detail in the wild. Tylochromis are maternal mouthbrooders that do not form lasting pair bonds: the female alone incubates and protects the brood, and the male's contribution ends essentially at fertilisation. That mode implies the familiar mouthbrooder social structure — males that court and spawn transiently rather than holding a mate, and no durable biparental territory of the kind cave-spawning cichlids defend. Specific accounts of pair formation, spawning colours and courtship sequence for sudanensis itself are thin in the literature, and that gap is worth stating plainly rather than filling with invention; the behaviour is inferred from the consistent maternal, non-pair-bonding pattern reported across the genus by Stiassny and by Lamboj.
Breeding
Tylochromis sudanensis is a maternal mouthbrooder. After spawning, the female takes the eggs into her buccal cavity and incubates them there, guarding the developing young until they are released as free-swimming fry — the male plays no part in brood care. Clutch and egg figures specific to sudanensis are not well established in the published record, but the genus offers a clear template: in the better-studied Tylochromis polylepis females have been found carrying on the order of 100 large eggs roughly 0.5 in across, the classic mouthbrooder trade-off of a small clutch of big, yolky eggs that hatch into well-developed fry. A comparable modest fecundity of large eggs is the reasonable expectation for sudanensis. FishBase rates the species as having high resilience, with a minimum population doubling time of under fifteen months — consistent with a fish that, while not enormously fecund per spawning, breeds readily under good river conditions. Wild spawning triggers (likely tied to the seasonal flood pulse, as in many Sudanian floodplain fishes) are not documented in detail for the species.
In the aquarium
Tylochromis sudanensis is rarely seen in the hobby; it reaches the trade only occasionally as a West African oddity, and most of what guides keeping it is the general profile of the genus rather than a long captive track record for this species specifically. It is a substantial fish — to roughly 8 in SL (around 10 in total length) — and a genuine sand-sifter, so the non-negotiable requirements are a long tank with a generous open footprint, an open bed of fine sand it can work through constantly, and the room to do so. A four-foot tank is a realistic minimum for a single adult, with more length better for a group; rockwork-stuffed setups of the kind built for mbuna are exactly wrong for an open-substrate roamer like this.
Water should mirror the warm, circumneutral-to-mildly-alkaline Sudanian rivers it comes from: temperature in the mid-20s to around 86 °F and pH from roughly 6.5 to 8.0, with moderate hardness. Tylochromis as a genus are noted for a marked intolerance of low oxygen, so strong, well-oxygenated filtration is essential — a sand-sifter kicks up a great deal of detritus, and an under-aerated or crowded tank is a real risk to these fish. Diet is straightforward for an omnivore of this kind: a varied regime of quality sinking pellets, frozen invertebrates (bloodworm, mysis and similar) and some vegetable or algae-based matter covers its natural plant-and-invertebrate leanings.
Temperament is the typical large-Tylochromis profile — substrate-moving and moderately assertive rather than viciously predatory; the bigger compatibility question is scale and shared conditions, not malice. Tankmates should be robust species that suit the same large, warm, hard-ish, sand-floored setup and are not so small as to be incidental prey. As with other open-substrate sifters, it is unwise to crowd it with visually similar congeners that might compete for the same niche. This is an advanced keeper's fish chosen for behaviour and rarity, not a beginner's centrepiece, and one to take on only with the space and filtration it genuinely needs.
Conservation
The IUCN Red List assesses Tylochromis sudanensis as Least Concern, in an assessment dated 10 January 2020 by I. Diallo, A. Awaïss, P. Lalèyè and T. Moelants under the Pan-Africa Freshwater Biodiversity Assessment, with the population trend recorded as unknown. The listing reflects a wide distribution across several major West African and west-central African river basins — Niger, Benue, Cross, Wouri and the Lake Chad system — rather than any evidence of abundance, and the species carries no CITES or CMS listing. FishBase rates it low in fishing vulnerability and high in resilience, so it is not flagged as a fishery concern. The honest framing is that the fish itself is not in documented trouble, but the Sudanian river systems it depends on are under broad and growing pressure: the rivers of the Sahel and savanna belt face damming, water abstraction, agricultural runoff, deforestation of gallery forest, and the disruption of the seasonal flood pulse that floodplain-spawning fishes rely on. None of these is recorded as a specific, present threat to this particular cichlid, but they are the regional backdrop against which its long-term status should be read; as a widespread habitat generalist it is far less exposed than the many narrow-range endemics of the same basins.