Taxonomy & naming
Pseudohemiodon amazonum was described by Delsman in 1941 and is recognised as a valid species in the Catalog of Fishes (Eschmeyer, CAS). It belongs to the subfamily Loricariinae — the whiptail and flatface armoured catfishes — within the family Loricariidae. The original combination has carried through to the current binomial without subsequent reassignment to another genus.
The genus Pseudohemiodon comprises a group of flattened, sand-associated whiptails distributed across the major river basins of tropical South America. P. amazonum is the species whose epithet directly references the Amazon, where it occurs in the lower part of the basin.
Morphology
Pseudohemiodon amazonum is a small whiptail catfish reaching about 3.5 in in standard length. Like other members of the genus it has the strongly depressed, dorsoventrally flattened body typical of sand-dwelling Loricariinae, with the head and forebody broad and flat and the body tapering rearward into a slender caudal peduncle. The body is encased in the overlapping bony plates characteristic of the family.
Detailed meristic and pattern data for this species are not reproduced here beyond the published maximum size; finer diagnostic features are best taken from the original description. Coloration and specific plate counts for P. amazonum are not characterised in the consulted sources.
Habitat
The species is restricted to freshwater of the lower Amazon River basin in South America. It is a demersal, tropical fish — living in close association with the bottom rather than the water column.
Members of Pseudohemiodon are typically found on open sand and fine sediment, where their flattened bodies allow them to lie flush against or partly buried in the substrate. Specific water-chemistry measurements from the type locality or known collection sites are not published in the consulted sources; the broad expectation for lower-Amazon lowland rivers is warm, soft, near-neutral to mildly acidic water, but no measured values are available for this species.
Feeding
The diet of Pseudohemiodon amazonum is not characterised in the consulted sources. FishBase assigns the species a low trophic level (about 2.6), consistent with a largely detritus- and micro-invertebrate-based diet.
Sand-dwelling congeners are benthic feeders that sift the substrate, taking detritus, biofilm, and small invertebrates from among the sand grains. P. amazonum is likely to feed in this manner, but direct dietary observations for the species have not been published.
Mating
No data on courtship or mating behaviour have been published for Pseudohemiodon amazonum.
Breeding
No breeding data have been published for Pseudohemiodon amazonum. Several Loricariinae are lip-brooders, the male carrying the egg mass attached to the underside of the head and body, but whether P. amazonum follows this pattern has not been documented in the consulted sources.
In the aquarium
Pseudohemiodon amazonum is not a commonly traded aquarium fish, and dedicated husbandry information for the species is not published. As a small, flattened sand-dweller, it would require a soft sand substrate, gentle flow, and clean, well-oxygenated water reflecting its lower-Amazon origins.
Specific recommendations on diet, tankmates, and breeding in captivity cannot be given responsibly without published data for this species; the general requirements of sand-dwelling Loricariinae are the only useful guide.
Conservation
The IUCN Red List assessed Pseudohemiodon amazonum as Least Concern in 2020. The species is not listed under CITES.
No specific threats to the species have been documented in the consulted sources. As with other lower-Amazon fishes, broad-scale pressures on the basin — deforestation, sedimentation, and hydrological alteration — are background concerns, but at present the species is not considered threatened.