Taxonomy & naming
Pseudohemiodon lamina was described by Albert Günther in 1868 in the Annals and Magazine of Natural History (Series 4, volume 1, number 6, article 56, page 478), based on material from Xeberos (also spelled Jeberos), a locality in the upper Amazon basin of Peru. The original combination was Loricaria lamina; the species was subsequently placed in Pseudohemiodon, where the Catalog of Fishes (Eschmeyer, CAS) recognises it as the valid name. P. lamina is the type species of the genus Pseudohemiodon.
The genus Pseudohemiodon belongs to the subfamily Loricariinae — the whiptail catfishes — within the family Loricariidae. Loricariinae are characterised by an elongate, often extremely depressed body, a long filamentous caudal extension in many species, and the absence of an adipose fin. Ferraris (2007, Zootaxa 1418) provides the most recent comprehensive checklist treatment of this group.
Morphology
Pseudohemiodon lamina reaches approximately 6.5 in standard length (SL). The body is extraordinarily flattened dorsoventrally — a shape taken to an extreme even within the whiptail lineage — and the head is broad and depressed, giving the fish a spatula-like or 'blade' profile when viewed from above. The armour of bony scutes is reduced along the ventral surface relative to many other loricariids, consistent with a fish that spends its time pressed against soft sediment. Coloration is typically pale sandy-brown above, matching riverbottom substrate, with a paler underside.
The caudal filament, a feature common across much of Loricariinae, is present. The eyes are positioned dorsally, as expected in a bottom-resting ambush-posture fish. Sexual dimorphism in this species is not well documented in the literature; however, males in related Pseudohemiodon are known to develop modest odontodal growth and to brood eggs on the body — a characteristic that may apply here but has not been formally described for P. lamina specifically.
Habitat
Pseudohemiodon lamina is known from the upper Amazon basin of Peru, with the type locality at Xeberos (Jeberos), Loreto. This region is characterised by large, sediment-rich lowland rivers and their tributaries flowing through the Amazon floodplain. As a benthopelagic sand-dweller, P. lamina is expected to inhabit sandy or fine-gravel river margins and backwaters where the substrate matches its pale cryptic coloration.
FishBase records environmental parameters consistent with warm Amazonian lowland conditions: temperature 72–79 °F, pH 6.0–7.5, and soft to moderately soft water (dH ≤10). The fish is classified as a primary consumer at trophic level 2.0, consistent with grazing biofilm, algae, and fine organic matter from soft substrates.
Feeding
Consistent with its position as a low-trophic benthic grazer, P. lamina feeds primarily on fine biofilm, diatoms, and organic detritus scraped from sandy and muddy substrates. The flattened ventral mouth is well-positioned for grazing soft sediment surfaces. In the aquarium, a fine sand substrate that allows natural foraging behaviour is important. Sinking algae wafers, spirulina tabs, and blanched vegetables (courgette, cucumber) represent suitable supplementary foods. Light offerings of frozen invertebrates may be accepted but are not a dietary priority for this essentially herbivorous grazer.
Mating
Mating behaviour in P. lamina has not been documented in captivity in any published source. Based on the biology of the genus Pseudohemiodon, males are expected to establish and defend territories on sandy substrates, developing modest odontodes during breeding condition. The extremely flattened body form of Pseudohemiodon species is related to their reproductive strategy — males of the genus brood eggs pressed beneath the body or on the lip pad, and selecting a suitably sheltered stretch of sand is presumably a component of courtship behaviour.
Females are expected to be distinguishable from males by a broader body profile when gravid and by the absence of pronounced odontodal development.
Breeding
Pseudohemiodon lamina is a paternal brooder. The PlanetCatfish database includes an image captioned 'male guarding eggs', confirming that the male assumes responsibility for the clutch — consistent with the egg-brooding strategy documented across Pseudohemiodon, where the male holds eggs against his body or beneath the broad ventral surface rather than depositing them in a cave. This open-substrate, body-brooding strategy sets Pseudohemiodon apart from the cave-spawning Hypostominae.
Beyond this photographic confirmation of paternal care, no detailed breeding account for P. lamina in captivity appears in the literature reviewed. Keepers attempting to breed this species should provide a deep, fine sand substrate, soft slightly acidic water, and a temperature in the lower portion of the species' range, as seasonal temperature drops often serve as a breeding trigger in South American catfishes.
In the aquarium
Pseudohemiodon lamina is rarely encountered in the hobby; no common name is registered in the PlanetCatfish database, and only a small number of individuals have been spotted and kept by enthusiasts. The species is a specialist's fish — its requirements are specific, its behaviour is cryptic, and its availability from collectors is irregular.
The tank should be set up with a deep layer of fine, smooth sand as the primary substrate; coarse gravel is unsuitable for a fish that rests on and forages through soft sediment. Bright lighting should be avoided; the fish is secretive and will be more active and visible in subdued illumination or with areas of shade from surface floating plants. Water parameters should reflect the upper Amazon origin: temperature 72–79 °F, pH 6.0–7.5, soft water (dH ≤10). Excellent filtration and regular water changes are essential, as with all loricariids. Tank size should be appropriate for the eventual adult length of around 6.5 in SL — a minimum footprint of 90 × 17.5 in is advisable for a single specimen, larger for a pair.
Competition at feeding is a concern: P. lamina is a gentle, low-profile grazer and will be outcompeted by boisterous or fast-moving tankmates for sinking foods. Peaceful, similarly-sized soft-water species are the best companions. Other loricariid whiptails of similar size can be housed together if the tank is large enough and multiple feeding stations are provided.
Conservation
The IUCN Red List assessed Pseudohemiodon lamina as Least Concern in 2014 (IUCN ID 49830067), noting no major identified threats and assuming a stable population trend. The species' range within the upper Amazon basin of Peru encompasses some of the most extensive continuous tropical forest in South America, and no specific pressures targeted at this species have been documented.
The broader Amazon basin faces ongoing habitat pressures from deforestation, agricultural encroachment, and river modification, and sandy-substrate specialists may be affected by increased sedimentation from catchment disturbance. However, at the time of assessment, P. lamina was not considered to face threats at a level warranting a higher risk category.