Taxonomy & naming
Anostomus brevior was formally described by Jacques Géry in 1961, in the Bulletin du Muséum National d'Histoire Naturelle, from material collected in the Rivière Camopi, a tributary of the Oyapock River in French Guiana. It sits in the family Anostomidae — the headstanders — within the order Characiformes, and in the genus Anostomus, a small group of elongate, torpedo-shaped characins characterised by an upturned mouth and a habit of grazing at a steep head-down angle.
The genus name Anostomus is built from Greek ana- ("up") and stoma ("mouth"), describing the upward-angled mouth shared by the group; the species epithet brevior is Latin for "shorter", distinguishing this species from its longer-bodied congeners such as A. anostomus and A. ternetzi. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) treats Anostomus brevior as a valid, currently recognised species; it is restricted to the Oyapock River basin and has also been recorded from Suriname.
Morphology
Anostomus brevior has the classic headstander body plan: an elongate, laterally compressed, torpedo-shaped trunk, a small terminal mouth angled sharply upward, and a forked tail. FishBase records a maximum size of 4.5 in standard length, making it one of the more modestly sized members of its genus and considerably smaller than the striped headstander, A. anostomus.
As in other Anostomus species, the resting and foraging posture is diagnostic: the fish holds itself at a steep, often near-vertical head-down angle while grazing sandy or wood-covered surfaces, a stance that gives the genus its common name. Colour pattern data specific to A. brevior were not returned by the cache; hobbyists should expect the general Anostomus look of a streamlined body marked with dark longitudinal striping, though exact pattern details are not confirmed here and should not be guessed.
Habitat
Anostomus brevior is known from the Oyapock River basin on the French Guiana–Brazil border, with its type locality in the Rivière Camopi, and it has also been recorded in Suriname. Within that range it occupies shallow river and creek habitat with sandy substrate and strong current — fast-flowing, well-oxygenated Guiana Shield water rather than still backwaters.
Specific published water-chemistry data for A. brevior were not returned by the cache, but comparable Guiana Shield and broader Neotropical river systems typically run soft to neutral, with clear-to-slightly tannin-stained water and temperatures in roughly the 72–82 °F range for related Anostomus species. Structure in the wild consists of sand and rock over which the fish grazes, with current rather than dense vegetation shaping the habitat.
Feeding
Anostomus brevior is an algae- and aufwuchs-grazer: in the wild it works sandy and rocky surfaces in its steep head-down posture, rasping off algae and the biofilm layer of diatoms, detritus and small invertebrates that grows on submerged surfaces in current. This places it squarely among the grazing headstanders rather than the predatory or scale-eating characins found elsewhere in this family group.
In the aquarium, A. brevior should be offered a diet built around vegetable matter — algae-based foods, spirulina flakes or wafers, and fresh blanched vegetables such as courgette or spinach — supplemented with occasional protein such as small live or frozen foods. As a grazer, it will also pick at soft-leaved plants and algae growths in a planted tank, so aquarists should choose robust, fast-growing or algae-tolerant plants rather than delicate species.
Mating
Published detail on courtship behaviour specific to Anostomus brevior is sparse. FishBase notes that distinct pairs form and breed in densely grown, weedy places, which points to pair-based rather than mass-shoal spawning, but does not describe courtship display, triggers, or timing in detail. No reliable external sexual dimorphism for this species was returned by the cache, so this article does not assert a way to visually sex the species; data is sparse here and should not be guessed at.
Breeding
Anostomus brevior is documented as an egg-scatterer that spawns in densely vegetated, weedy areas, and it is rarely bred in captivity — the cache does not point to an established aquarium-breeding protocol for this species, in keeping with the wider pattern among headstanders, where only a handful of Leporinus and Anostomus species have been spawned by hobbyists and some Leporinus are farmed commercially. There is no evidence of parental care in this species; once eggs are scattered among vegetation, the adults do not appear to guard or tend them.
Aquarists interested in attempting a spawn should not expect a reliable, repeatable home-breeding pathway comparable to egg-scatterers such as silver dollars; this is a species better approached as a long-lived display fish than a breeding project, and any claims of consistent aquarium breeding should be treated with caution absent stronger documentation.
In the aquarium
Anostomus brevior stays a manageable size — up to about 4.5 in SL — which makes it more tractable for a home aquarium than many of its larger characin relatives, but it still needs a long tank with open swimming room and, importantly, strong water movement: this is a current-adapted river grazer, not a still-water fish, and a powerhead or high-flow filter return will suit it far better than a placid setup. Sandy or rocky substrate with driftwood to graze on echoes its wild habitat and gives it natural foraging surfaces.
As with other Anostomus, A. brevior should be kept in a small group where space allows, since many headstanders are territorial toward their own kind and toward similarly shaped tankmates, and several relatives in the genus — including the well-known striped headstander — have a reputation as fin-nippers as they mature. Choose tankmates that are not slow, long-finned, or similarly elongate in body shape, and provide enough swimming space and visual breaks (wood, rockwork) to diffuse aggression. Its largely herbivorous, grazing diet also means it will sample soft aquarium plants, so plant choice should account for that.
Conservation
Anostomus brevior is assessed by the IUCN Red List as Least Concern. It has a genuinely restricted natural range — the Oyapock River basin of French Guiana and Brazil, with records from Suriname — but within that range it is described as relatively abundant and social, occurring in groups in its preferred shallow, sandy-bottomed river and creek habitat.
No specific major threats to A. brevior were returned by the cache. As with other Guiana Shield endemics, the general long-term pressures on the region's freshwater systems — small-scale mining, deforestation-linked sedimentation and water-quality change — are relevant background considerations even though the species itself is not currently classified as threatened.