Taxonomy & naming
Ichthyoelephas humeralis was described by Albert Günther in 1860 as Prochilodus humeralis, in his "Second list of cold-blooded vertebrata collected by Mr. Fraser in the Andes of western Ecuador," based on a type specimen (BMNH 1860.6.16.197) collected from the Babahoyo River channels near Samborondón, Guayas Province, Ecuador. It was later moved into the genus Ichthyoelephas, which the Catalog of Fishes (Eschmeyer, California Academy of Sciences) recognises as a small genus of two valid species within Prochilodontidae, the flannelmouth or bocachico family, itself part of the order Characiformes.
Older literature and some regional sources may still carry the original combination Prochilodus humeralis; this article follows the currently accepted genus, Ichthyoelephas. A karyotype study (2n = 54 biarmed chromosomes: 32 metacentric + 22 submetacentric) confirms the species as cytogenetically distinct within the family. The genus name, from Greek ikhthys (fish) and elephas (elephant), is generally read as an allusion to the large, fleshy, trunk-like protrusible lips shared by the family's detritivorous grazers.
Morphology
Ichthyoelephas humeralis has the elongated, moderately compressed body typical of Prochilodontidae, with a small, downturned mouth bearing thick, protrusible lips adapted for rasping organic matter and biofilm from rocks, wood and sediment rather than for grasping prey. FishBase records a maximum of about 9.5 in standard length in males, but the species is documented reaching at least 15.5 in total length as an adult — a substantial fish by the standards of this site's smaller characins, and one that should not be mistaken for a nano or even a typical community species.
As in other prochilodontids, colouration is generally a subdued silver-grey along the flanks, and the species name humeralis ("of the shoulder") likely references a humeral marking noted in Günther's original description, though the cache sources available here do not detail its exact form or persistence in adults. Data on fin counts, scale counts and other diagnostic morphometrics beyond the type description are sparse in the sources consulted for this article.
Habitat
This species is a western Ecuador endemic, confirmed from the Guayas and Santiago River basins draining the Pacific slope of the Andes, with occurrence records concentrated in that region and no evidence of a wider South American range. It is described as benthopelagic in freshwater tropical rivers — living and feeding near the bottom of flowing water rather than in open midwater — consistent with its role as a substrate grazer.
Detailed water-chemistry parameters (temperature range, pH, hardness) specific to the Guayas and Santiago basins are not given in the sources consulted here, so none are asserted; these are lowland-to-piedmont Andean river systems on Ecuador's Pacific slope, distinct from the Amazon-basin rivers that dominate this family elsewhere in South America.
Feeding
Ichthyoelephas humeralis is a detritivore, feeding primarily on detritus, algae and biofilm scraped from submerged surfaces in Andean river channels — the same ecological role played by its relatives Prochilodus and Semaprochilodus elsewhere in South America, where these grazers are ecologically important recyclers of organic matter in river systems. This diet is a direct match to its lip and mouth morphology, described above, rather than to any predatory habit.
No aquarium feeding data is available in the sources consulted, unsurprising for a species that is essentially unknown in the hobby (see "In the aquarium" below); wild individuals are grazers of the river bottom, not opportunistic omnivores or predators.
Mating
Data sparse: none of the sources consulted here document courtship behaviour, spawning triggers, or external sexual dimorphism for Ichthyoelephas humeralis. Given its placement in Prochilodontidae alongside the well-studied migratory spawners Prochilodus and Semaprochilodus, a seasonal, flow-cued spawning migration is plausible, but this article does not assert that mode for this species without direct confirmation, which the cache does not provide.
Breeding
There is no documented aquarium or captive-breeding record for Ichthyoelephas humeralis in the sources consulted, and it is not a species kept or bred in the hobby. Its close relatives among the bocachico/flannelmouth characins are known as long-distance river migrators whose spawning is exploited commercially and, in some regions, supported by hormone-induced hatchery breeding for fisheries and aquaculture rather than achieved in home aquaria — FishBase specifically notes commercial importance in fisheries and aquaculture for this species, consistent with that pattern, though the sources here do not confirm hatchery propagation methods specific to I. humeralis. This article does not assign a specific breeding mode beyond that context, to avoid overstating what is actually documented.
In the aquarium
Ichthyoelephas humeralis is not an aquarium fish in any practical sense — it is a regional food fish of Ecuadorian rivers, reaching at least 15.5 in total length, and it is not traded, imported or kept in the hobby as far as the sources consulted here indicate. Its inclusion in this atlas is for completeness of the minor-characin groups within the broader Piranhas & Pacus family, not as a stocking recommendation.
Anyone encountering the species would be doing so through Ecuadorian fisheries or field biology rather than the aquarium trade; a fish of this size and this specialised detritivorous, river-grazing ecology would in any case be entirely unsuited to home aquarium life.
Conservation
The IUCN Red List assesses Ichthyoelephas humeralis as Near Threatened, an assessment dated October 2020. As a single-region endemic restricted to the Guayas and Santiago basins of western Ecuador, it is vulnerable to the pressures typical of Andean Pacific-slope rivers — habitat degradation, water abstraction and fishing pressure, given its recognised commercial importance in local fisheries — though the sources consulted here do not break down the specific threats behind the NT assessment in further detail.
Because the species supports commercial fisheries and aquaculture in Ecuador per FishBase, harvest pressure is a plausible contributing factor to its threatened-but-not-yet-endangered status, alongside the general vulnerability that comes with a restricted, single-country range.