Taxonomy & naming
Cteniloricaria platystoma was described by Albert Günther in 1868 in the Annals and Magazine of Natural History (Series 4, volume 1, number 6, art. 56, p. 478) as Loricaria platystoma, from type material labelled 'probably Suriname'. The lectotype (BMNH 1866.8.14.124, 7 in SL) and a single paralectotype (BMNH 1866.8.14.128) are deposited at the Natural History Museum, London; the lectotype was designated by Isbrücker in 1979.
The Catalog of Fishes (Eschmeyer, CAS; updated June 2026) recognises the valid combination as Cteniloricaria platystoma (Günther 1868). The species has also appeared in the literature under Harttia platystoma (placed in Harttia by Rapp Py-Daniel & Oliveira, 2001; Provenzano et al., 2005), but CoF currently treats Cteniloricaria as the valid genus for this species following the most recent combined molecular–morphological phylogeny of Loricariinae (Londoño-Burbano & Reis, 2021).
The genus Cteniloricaria — erected by Isbrücker (in Isbrücker & Nijssen, 1979) with this species as type — is diagnosed from the closely related Harttia by having the abdomen completely covered by medium-sized polygonal plates (vs. partially naked or with small platelets), the tip of the snout covered with plates (vs. naked), and a distinctive dark half-moon band on the caudal-fin base spanning all rays of both lobes (Londoño-Burbano, Mendonça & Reis, 2021). Cteniloricaria currently contains two valid species: C. platystoma and C. napova Covain & Fisch-Muller, 2012. No L-number has been assigned.
Morphology
Cteniloricaria platystoma reaches approximately 8 in in total length, making it the larger of the two Cteniloricaria species. The body follows the Loricariinae pattern: broadly and strongly depressed, with a flat ventral surface well suited to pressing against the substrate, and a long caudal peduncle narrowing toward the tail. The cross-section shifts from dorsoventrally flattened anteriorly to laterally compressed in the caudal region.
The most distinctive diagnostic marking is the dark transverse, half-moon shaped band at the base of the caudal fin, spanning the bases of all rays on both upper and lower lobes — a feature that separates Cteniloricaria from Harttia (where only a smaller blotch occurs). Overall body coloration is cryptic: grey-brown to olive-brown above, often with an indistinct, marbled or blotchy pattern; pale below. C. platystoma is distinguished from its congener C. napova by lacking the distinctly spotted coloration of the latter.
The abdomen is fully covered by medium-sized polygonal bony plates — a complete armour unlike the partially plated condition of Harttia. The tip of the snout bears plates rather than naked skin. The mouth is ventral and wide: platystoma (from Greek platys, flat/broad, and stoma, mouth) is a direct reference to this wide, flat oral disc. Anatomically, Cteniloricaria belongs to the tribe Harttiini within Loricariinae and shares with Harttia a general body plan adapted to life over sandy, mixed-substrate river beds.
Habitat
Cteniloricaria platystoma is distributed across the main coastal drainages of the Guiana Shield — specifically the north-flowing rivers from the Sinnamary in French Guiana westward through Suriname (Suriname River, Saramacca, Coppename, Gran Rio, Marowijne/Maroni, Suriname River, Corantijn) to the Essequibo basin in Guyana (Londoño-Burbano et al., 2021; Covain et al., 2012). This distribution is essentially restricted to rivers that drain directly into the Atlantic from the Guiana Shield highlands.
Field records from GBIF and collection data describe the species as occurring on sandy bottoms in the mainstream river and major tributaries (Fishes of the Mitaraka Mountains, French Guiana). It favours sandy substrate and has been observed only in underwater inventories at sites in French Guiana (Londoño-Burbano et al., 2021). The type of habitat is sandy-bottomed river channels, consistent with conditions typical for the coastal rivers of Suriname and French Guiana — generally clear to moderately turbid, warm (75–82 °F), slightly acid to near-neutral water with low to moderate conductivity.
The genus shows a notably disjunct distribution: C. platystoma occupies north-flowing Guiana Shield coastal rivers, while C. napova (its Amazon-tributary congener) occurs in south-flowing headwaters of the Paru de Oeste and Cuminapanema rivers. This split is interpreted as the result of ancient headwater capture events across the Guiana–Amazon drainage divide (Londoño-Burbano et al., 2021).
Feeding
Detailed dietary data are not available for Cteniloricaria platystoma; no published stomach-content analyses have been reported for the species. The genus ecology points to sandy-substrate benthic foraging — consistent with other Harttiini whiptails that sift sand and detritus for fine organic particles, micro-invertebrates, and associated micro-organisms.
FishBase assigns C. platystoma a trophic level of approximately 2.5, the standard estimate for benthic detritivores of similar body plan and habitat. The wide, flat oral disc is suited to surface-level sifting over sandy bottoms rather than rasping hard substrates: the dentition of Cteniloricaria is of the brush-tooth type found across many Loricariinae, not the spatulate xylophage teeth of Panaque or the fine multiple-cusped teeth of Ancistrus.
In the aquarium, the suedamerikafans.de database does not flag Cteniloricaria platystoma as a plant eater; dietary treatment should follow the general approach for sandy-substrate Loricariinae: sinking omnivore wafers, spirulina-based foods, blanched vegetable matter, and frozen invertebrate supplements (mosquito larvae, daphnia). Fresh water flow over the substrate may help expose invertebrates and trigger natural foraging behaviour.
Mating
Courtship behaviour in Cteniloricaria has not been described in the scientific literature. The genus is classified within the Harttiini, a tribe whose reproductive strategies are less extensively studied than those of the Pseudohemiodon group; substrate brooding (rather than the abdomino-lip brooding found in Pseudohemiodon and Rhadinoloricaria) is indicated for Harttiini by analogy with the general taxonomy.
The suedamerikafans.de catfish database notes Cteniloricaria as a substrate breeder from genus-level data, suggesting spawning on or near the riverbed substrate rather than in a cavity. This would align the genus with the typical whiptail pattern of depositing eggs on a hard surface or in a partially sheltered site rather than brooding them on the body.
Sexual dimorphism in this species has not been formally described. In many Loricariinae, males develop more pronounced interopercular or postcleithral odontodes during reproductive condition, and females become noticeably wider-bodied with a distended abdomen when gravid. Whether similar dimorphism is expressed in Cteniloricaria is not confirmed; keepers should examine the genital papilla, which differs in shape between sexes in most loricariids.
Breeding
No captive breeding of Cteniloricaria platystoma has been confirmed or published. The suedamerikafans.de database records captive breeding status as 'unknown' for the species. The fish rarely enters the ornamental trade; occasional specimens appear in Surinamese or French Guianese export lots but are not targeted commercially and are unlikely to be offered regularly in the hobby.
Given the substrate-brooder inference from genus ecology, a sandy-bottomed aquarium with some flat stones or smooth wood as potential spawning sites — combined with good flow and clean, well-oxygenated water — would be the logical starting conditions for any breeding attempt. Temperature targeting 77–81 °F with seasonal fluctuation mimicking the Guianese dry-wet seasonal pattern might provide additional stimulus.
Any documented captive reproduction of this species would represent a genuine gap-filler in the loricariid literature. The fact that C. napova — its congener from the Sipaliwini Savannah of Suriname — was observed alive in the field over sandy substrate in slow-flowing stream conditions (Londoño-Burbano et al., 2021) suggests both species are adapted to relatively clear, moderate-current habitats rather than high-energy rapids.
In the aquarium
Cteniloricaria platystoma is a specialist, rarely encountered fish that demands conditions closely approximating its natural sandy-substrate Guianese river habitat. It is not a pleco for the typical community aquarium; it is for the dedicated whiptail keeper prepared to maintain a large, sand-floored setup.
A minimum 47 in aquarium is recommended (suedamerikafans.de), providing a large open sandy area in which the fish can move, half-bury, and forage. Fine river sand at 2–3 in depth is essential; the species will press flat against the sand surface and may partially excavate shallow depressions. Moderate water flow — consistent with the sandy mainstream and tributary habitats of Suriname and French Guiana — should pass over the sand without scouring it excessively.
Temperature 75–82 °F, pH in the soft-acid to near-neutral range (6.5–7.5), and soft water are appropriate targets reflecting the low-conductivity, shield-river conditions of the Guiana coast. Keep nitrates low with regular partial water changes (25–30% weekly). With a total length approaching 8 in, this is a substantial fish that produces proportional waste; filtration must be sized accordingly.
Group keeping is recommended over individual housing (suedamerikafans.de). Sympatric species in Surinamese rivers include Harttia guianensis, Hemiancistrus medians, and Peckoltia otali, suggesting that mixed Loricariidae communities from the same region can be compatible. Avoid aggressive or large predatory tankmates. The distinctive caudal banding and flat, armoured body make this one of the more visually distinctive whiptails in a well-maintained biotope setup.
Conservation
The IUCN Red List assessed Cteniloricaria platystoma as Least Concern in October 2020, based on a distribution across multiple rivers of the Guiana Shield coastal drainage — an area with relatively intact forest cover and limited industrial development compared to other parts of the Neotropics. The species' occurrence across the Sinnamary (French Guiana), Suriname river system, and Essequibo basin in Guyana gives it a range spanning multiple river basins and national jurisdictions, reducing single-basin extinction risk.
However, the Guianas are not without threat. Small-scale gold mining (particularly alluvial orpaillage in French Guiana and Suriname) deposits mercury and causes riverbed disturbance — significant concerns for a sandy-substrate species. Deforestation along river corridors threatens both water quality and the organic inputs that sustain benthic food webs. The species' restriction to sandy-bottomed mainstream habitat may limit its ability to exploit alternative microhabitats if primary habitat is degraded.
The current distribution does not extend into Brazil except for the close congener C. napova in border areas; the disjunct biogeography documented by Londoño-Burbano et al. (2021) highlights the role of ancient drainage history in shaping this genus's range and underscores the importance of protecting intact Guiana Shield drainages as refugia for taxa with specialised habitat requirements.