Taxonomy & naming
Pterodoras rivasi was described by the Venezuelan ichthyologist Agustín Fernández-Yépez in 1950. It belongs to the family Doradidae, the thorny or talking catfishes of South America, within the genus Pterodoras — a small genus that PlanetCatfish notes contains only two recognised species. The Catalog of Fishes (Eschmeyer, CAS) is the governing authority for the valid name, and Doradidae as a whole has seen extensive taxonomic revision over the twentieth century as genera like Pterodoras, Doras and Oxydoras were separated and re-diagnosed; older literature and aquarium labels sometimes lump doradids under broader or outdated generic names, but Pterodoras rivasi is the currently accepted combination.
The genus name Pterodoras combines the Greek pteron ("wing" or "fin") with Doras, the type genus of the family, itself an old Greek word for a spear or leather shield — an allusion to the thorny, armoured build shared by the group. The species epithet rivasi honours a collector or colleague named Rivas, a common nineteenth- and twentieth-century convention in South American ichthyology; the exact dedicatee is not recorded in the sources consulted here.
Morphology
This is a big-bodied doradid: FishBase records a maximum size of 21.5 in standard length, placing adult Pterodoras rivasi well beyond the scale of a typical home aquarium. The head is broader than it is long, carrying small, dorsally positioned eyes and a subterminal mouth ringed by three pairs of sensory barbels used to probe the riverbed in the dark.
The body's defining feature is its armour: a row of 25–30 bony lateral scutes runs along each flank from behind the head to the base of the tail, each scute typically bearing a backward-pointing hook or spine. Like other doradids, it also carries a stiff, serrated, lockable spine at the leading edge of the dorsal fin and each pectoral fin — spines that can be rasped against their sockets to produce the audible "talking" or grunting sound doradids are known for, and that readily snag in a net. This species has no true scales; the skin and its bony plates make it, like other catfish, more sensitive than scaled fish to copper-based medications and should be dosed conservatively.
Habitat
Pterodoras rivasi is native to the Orinoco River basin of Colombia and Venezuela. GBIF records its type locality as the Arauca River in Venezuela, a major Orinoco tributary, and a dedicated trophic-ecology study (published via ResearchGate) confirms the species living in the floodplain habitats of that river. It is a demersal, freshwater species, spending its time near the riverbed rather than in open water.
As a large-river and floodplain fish of the Orinoco system, it experiences the seasonal flood pulse typical of South American lowland rivers — warm, well-oxygenated water during the wet season and constrained channels in the dry season. Specific water-chemistry figures (pH, hardness) were not captured in the available sources; treat any figure offered elsewhere with caution and default to warm, well-aerated, moderately soft-to-neutral lowland-river conditions typical of the Orinoco system.
Feeding
PlanetCatfish describes the genus Pterodoras as omnivorous nocturnal predators that often move in small groups over the riverbed. The dedicated trophic-ecology study on this exact species in the Arauca River indicates a diet built around whatever animal and plant material it can find and overpower on the bottom at night — consistent with the broader doradid pattern of opportunistic, largely carnivorous foraging.
Given its adult size of up to 21.5 in, Pterodoras rivasi should be treated as a genuine predator capable of swallowing any tankmate small enough to fit in its mouth. In captivity a fish of this scale would take large meaty foods — whole fish, prawn, and sinking pellet or pelleted carnivore diets — and any companion species must be too large to be swallowed.
Mating
None of the cached sources document courtship or spawning behaviour for Pterodoras rivasi specifically. Doradid catfishes as a family are not known for the parental-care strategies seen in some other catfish lineages (there is no evidence here of bubble-nesting, internal fertilisation, or mouthbrooding in this genus), but without a direct source describing this species' reproductive behaviour, the details of pairing, courtship or spawning triggers should be treated as data sparse rather than assumed.
Breeding
There is no record in the available sources of Pterodoras rivasi being bred in captivity, and given its large adult size — up to 21.5 in standard length — it is very unlikely to be spawned in a typical home aquarium even if it were kept long-term. Large doradid catfishes of this scale are generally not reproduced by hobbyists; where doradids do enter the trade in numbers, that supply typically comes from wild collection rather than captive breeding. Prospective keepers should not expect to breed this species and should assume any specimen in the trade was wild-caught.
In the aquarium
Pterodoras rivasi is a textbook size-trap species: it is often available as an inexpensive, thumb-sized juvenile, but FishBase's recorded maximum of 21.5 in standard length means an adult is a metre-class fish requiring a correspondingly enormous tank — realistically beyond what most home aquarists can provide, and closer to the territory of large public-aquarium or pond systems. Anyone considering this species should plan for its true adult size from day one, not the size it is sold at.
Beyond the size issue, husbandry follows general large-doradid rules. It lacks true scales and carries only bony scutes, so it is medication-sensitive — use copper and other treatments conservatively. Its dorsal and pectoral spines lock rigid and are serrated; they snag in aquarium nets and can jab the handler, so any necessary handling should use a container rather than a net. As a nocturnal fish it appreciates dim lighting and solid cover such as rockwork or wide pipes to retreat into during the day, becoming active after dark. Given its predatory size, tankmates must be too large to be eaten.
Conservation
The IUCN Red List assesses Pterodoras rivasi as Least Concern, based on an assessment dated 2 December 2020. The listing cites a wide distribution across the Orinoco basin in Colombia and Venezuela with no major identified threats at the global scale.
As with many Orinoco basin fishes, localised pressures such as habitat change along the Arauca River and other tributaries, and any collection for the aquarium trade or local fisheries, are not flagged as significant at the range-wide level in the current assessment, but the species' fortunes remain tied to the health of the Orinoco floodplain system it inhabits.