Taxonomy & naming
Pseudohemiodon unillano was described by Rojas-Molina, Provenzano and Ramírez-Gil in 2019 and is recognised as valid in the Catalog of Fishes (Eschmeyer, CAS). It belongs to the subfamily Loricariinae within the family Loricariidae.
The species was previously misidentified as Pseudohemiodon laticeps; the 2019 description separated it on the basis of its plating and body proportions. Diagnostic features given in the original work include an abdomen completely covered with small to medium irregular plates, a plateless ventral area in front of the gill opening, a head with straight sides, a narrow head and caudal peduncle, an oval body cross-section, and a uniform light-brown dorsum lacking transverse dark bands except for some markings on the caudal peduncle.
Morphology
Pseudohemiodon unillano reaches about 8 in in standard length, making it one of the larger members of its genus. The body is the strongly depressed, flattened form typical of sand-dwelling Loricariinae, with a narrow head and a narrow, tapering caudal peduncle, and an oval cross-section. Fin-ray counts given in the description are 7 dorsal soft rays and 5 anal soft rays.
Coloration is a uniform light brown on the dorsal surface, without the transverse dark bands seen in some relatives; what dark markings occur are concentrated mainly on the caudal peduncle. The abdomen is completely covered with small to medium irregular plates, while the area immediately in front of the gill opening is plateless ventrally — a combination used to distinguish it from P. laticeps.
Habitat
Pseudohemiodon unillano occurs in freshwater of the Orinoco River basin, specifically the Llanos (savanna plains) region of Colombia and Venezuela. It is a demersal, tropical fish.
According to the original description it inhabits rivers and flooded areas at elevations of roughly 443–1096 ft above sea level, in stretches of gentle slope, over sandy or clay bottoms. Its flattened body suits this open-bottom habitat, where it lies against the substrate. Specific water-chemistry measurements (temperature, pH, hardness) are not published in the consulted sources.
Feeding
The diet of Pseudohemiodon unillano is not characterised in the consulted sources. FishBase assigns it a low trophic level (about 2.4), consistent with a benthic detritivore that sifts sand and fine sediment for detritus, biofilm, and small invertebrates, as is typical of sand-dwelling whiptails. Direct dietary observations for the species have not been published.
Mating
No data on courtship or mating behaviour have been published for Pseudohemiodon unillano.
Breeding
No breeding data have been published for Pseudohemiodon unillano. As with other members of the genus, reproductive behaviour for this recently described species remains undocumented in the consulted sources.
In the aquarium
Pseudohemiodon unillano is a recently described species and is not established in the aquarium trade; dedicated husbandry information is not published. As a large, flattened sand- and clay-bottom dweller, it would require a soft substrate, ample floor space, gentle flow, and clean water reflecting its Orinoco-Llanos origins.
Specific recommendations on diet, tankmates, and captive breeding cannot be given responsibly without published data for this species.
Conservation
The IUCN Red List assessed Pseudohemiodon unillano as Least Concern in 2020. The species is not listed under CITES.
No specific threats have been documented for the species. Broad pressures on the Orinoco basin and its Llanos rivers — agricultural runoff, sedimentation, and hydrological change — are background concerns, but the species is not currently considered threatened.