Taxonomy & naming
Corydoras stenocephalus was described in 1942 by Carl Eigenmann and William Ray Allen, from western Amazonian material. The epithet stenocephalus — from the Greek stenos, 'narrow', and kephalē, 'head' — captures the elongate, narrow-snouted head that is its most obvious feature. It belongs to the family Callichthyidae, the armoured catfishes, in the subfamily Corydoradinae.
The taxonomy of the group was overhauled in 2024, when Dias, Tencatt and colleagues published a phylogenomic revision splitting the unwieldy old genus Corydoras among several resurrected genera. Crucially, the long-snouted species — the so-called Lineage 1 of earlier molecular work — are the group that retains the name Corydoras sensu stricto, anchored on the type species Corydoras geoffroy. C. stenocephalus is a long-snouted, western-Amazon cory of exactly this kind, and it accordingly stays in Corydoras under the new scheme rather than moving to Hoplisoma, Gastrodermus or another of the resurrected genera. So here the familiar name and the current lineage name coincide: Corydoras stenocephalus.
Morphology
This is a moderately sized cory reaching about 2.5 in in standard length, distinguished from the common blunt-faced corys by its long, narrowly tapered snout — the 'narrow head' of the name. The body is the usual armoured cory plan: deep and flat-bellied, clad in two overlapping rows of bony scutes that meet in a dorsal ridge, with three pairs of barbels around the downturned mouth. The long snout is an adaptation for probing more deeply and selectively into the substrate than the short-snouted forms.
The colour is a pale tan to greyish body overlaid with fine dark spotting or reticulation that condenses into a darker pattern along the flank, with a dark marking through the eye region; the fins are largely clear to lightly spotted. The dorsal, pectoral and adipose fins each bear a stiff leading spine. As in most corys, females reach a larger, rounder size than males.
Habitat
Corydoras stenocephalus is a western-Amazon fish, recorded from eastern Ecuador and the Ucayali River basin of Peru, with additional records from the Machado (Ji-Paraná) River basin in Rondônia State, Brazil. This places it across the upper Amazon and its south-western tributaries, in warm lowland rainforest waters.
It is a benthic fish of quieter river and stream habitats — sandy and silty margins, channels and pools with leaf litter and submerged wood, typically over soft substrate it can sift. These are warm, soft, often slightly acidic to neutral waters, broadly in the 72–79 °F range with pH around 6.0 to neutral. Like all corys it is a facultative air-breather, surfacing to gulp air and absorb oxygen through a vascularised hindgut, an adaptation for the warm, sometimes oxygen-poor shallows of the Amazon lowlands.
Feeding
Corydoras stenocephalus is a benthic omnivore and detritivore, and its long snout makes it a more pointed forager than the blunt-faced corys. It works the bottom, driving its snout and barbels into sand and silt to taste out small invertebrates, insect larvae, worms, micro-crustaceans and organic detritus, expelling cleaned substrate through the gills. In the aquarium it takes sinking pellets, frozen bloodworm and brine shrimp and other small foods, and like all corys benefits from a varied diet rather than a reliance on tankmates' leftovers.
Mating
Corys are egg-laying shoalers with no pair bond and a distinctive courtship. A ready female cleans a spawning site and the group becomes active; a male takes up the classic 'T-position' at right angles to her head, and she appears to take his milt into her mouth. Sperm is thought to pass rapidly through her gut to fertilise the few eggs she holds in a pelvic-fin basket, which she carries to the cleaned surface and presses into place. The sequence repeats a few eggs at a time. Detailed spawning observations for C. stenocephalus specifically are scarce, but it is expected to follow this group-wide pattern.
Breeding
There is little aquarium breeding documentation specific to Corydoras stenocephalus; long-snouted corys are kept less often and bred less readily than the hardy short-snouted trade species. As a member of the genus it is expected to be a T-position egg-scatterer triggered by cooler, large water changes that imitate the rainy season, laying small batches of adhesive eggs on cleaned surfaces with no parental care — adults will eat the eggs, so breeders remove eggs or parents. Honest note: clutch size, fry development and reliable spawning triggers for this species are not well recorded, and most fish in trade are wild-caught rather than captive-bred.
In the aquarium
Corydoras stenocephalus is an occasional import rather than a staple, and is a little more demanding than the bronze or peppered corys — it wants clean, warm, soft water and is less tolerant of the broad abuse the trade workhorses shrug off. As with every cory it must be kept in a group of six or more; kept singly or in pairs it is stressed and withdrawn. Give a group a footprint of at least 23.5–31.5 in, since bottom area matters more than height.
Substrate is critical for any cory and doubly so for a long-snouted, sand-sifting species: provide soft sand or very smooth fine sand, never sharp or coarse gravel, which erodes and infects the barbels and snout. Keep the bottom clean and the water warm (about 72–79 °F), well-filtered, well-oxygenated and changed regularly, and keep it on the soft, slightly acidic side to match its western-Amazon origin. It is peaceful and suits a quiet community of tetras, small characins and dwarf cichlids. The usual cory cautions apply: net spines catch easily (use a cup), and a distressed cory can release skin toxins lethal in the confined volume of a transport bag.
Conservation
The IUCN Red List assesses Corydoras stenocephalus as Least Concern (assessed 2014). It has a reasonably wide distribution across the upper Amazon of Ecuador, Peru and western Brazil, and the lowland forest rivers it inhabits remain extensive. As with all Amazonian fishes it is not immune to the broad pressures of deforestation, mining, agriculture and pollution that bear on its habitats, and a long-snouted cory traded as a wild-caught specialty carries more collection interest than the captive-bred workhorses — but as a species it is not currently considered threatened.