Taxonomy & naming
Hypostomus brevicauda was described by Albert Günther in 1864 in the fifth volume of his Catalogue of the Fishes in the British Museum, under the original combination Plecostomus brevicauda. The two syntypes — specimens measuring 189.0 and 7.5 in SL, catalogued as BMNH 1864.1.19.16–17 — remain the primary basis for the species concept. The Catalog of Fishes (Eschmeyer, CAS) recognises Hypostomus brevicauda as a valid name, with Plecostomus brevicauda Günther 1864 as its sole prior combination.
The type locality is recorded only as 'Bahia' — referring to Bahia state in northeastern Brazil rather than a specific water body or collection point. Weber (2003) confirmed this imprecision persists in the literature and noted that some specimens subsequently referred to this species — including records from Córrego Traíra (municipality of Camacã) and the Rio Gongogi, a tributary of Rio de Contas — may in fact represent distinct taxa. The IUCN assessment (2018) explicitly acknowledges that taxonomic and distributional limits are unresolved, and a targeted revision has not yet been published. Until that revision appears, H. brevicauda is best treated as a provisional placeholder for material from coastal Bahia drainages rather than a fully characterised species.
Morphology
Morphological data are drawn entirely from the two nineteenth-century syntypes. Günther recorded a body length approaching 7.5 in SL and noted the caudal fin as 'obliquely subtruncated' — the feature that gave rise to the specific epithet (see Etymology). FishBase reports a maximum recorded length of 7.5 in SL based on the syntype series.
Beyond these basic measurements and the caudal fin shape, published morphological data are sparse. As a member of subfamily Hypostominae, H. brevicauda would share the family-level characters common to the group: a broad depressed head, ventrally placed sucking mouth armed with bifid teeth, paired lateral series of overlapping bony scutes, an erectile dorsal fin, and pectoral spines equipped with uncinate odontodes. Colouration of the type specimens in spirit is not recorded in sufficient detail to serve as a reliable field character. Any additional morphological claims beyond what the original description and syntype measurements support would be speculative.
Habitat
No habitat data are available for Hypostomus brevicauda. The type material carries only the broad geographic label 'Bahia', which encompasses a large and ecologically varied coastal-drainage system in northeastern Brazil — rivers ranging from small, seasonally intermittent streams on the semi-arid Agreste fringe to larger, permanently flowing rivers draining the wetter coastal Atlantic Forest zone further east.
Specimens tentatively referred to this species in secondary literature were reportedly taken from Córrego Traíra and Rio Gongogi in southern Bahia, both drainage units of the Atlantic coastal slope. However, as the IUCN assessment notes, the validity of these referrals has not been confirmed and the specimens may belong to other taxa. Habitat preferences, water chemistry tolerances, and microhabitat associations therefore remain entirely unknown.
Feeding
No dietary data have been published for Hypostomus brevicauda. As a hypostomid catfish, it presumably shares the scraping, algae-grazing, and detritivorous feeding mode that characterises most members of the subfamily: a ventral sucking disc with bifid teeth suited to rasping periphyton, biofilm, and detrital matter from submerged hard surfaces. Whether the species has any particular dietary specialisation — for example the spongiorophagy of some Hypostomus or the xylophagy of cochliodon-group relatives — is unknown and cannot be inferred from the available material.
Mating
No reproductive or behavioural data exist for Hypostomus brevicauda. Given that the species is known only from type material collected more than 160 years ago and has not been documented in the wild or aquarium since, mating behaviour has not been observed or described. Any account of courtship, territorial behaviour, or mate selection would be pure speculation.
Breeding
No breeding data are available. Hypostomid catfishes are broadly characterised as cavity spawners with paternal brood care — males guard and fan adhesive egg clutches within rock crevices, submerged wood cavities, or self-excavated burrows — but whether H. brevicauda follows this pattern is unconfirmed. The species has not been maintained in captivity or bred in the aquarium hobby.
In the aquarium
Hypostomus brevicauda has not been recorded in the aquarium hobby. The species has no trade name or L-number, and no live specimens are known to have been collected since the nineteenth-century type series. It is therefore not available to aquarists and cannot be recommended or evaluated as a captive subject. Any future encounter with a loricariid from Bahia coastal drainages tentatively identified as H. brevicauda would require expert taxonomic confirmation, given the unresolved validity of the species concept.
Conservation
The IUCN Red List assessed Hypostomus brevicauda as Data Deficient in November 2018, a classification that reflects a genuine absence of information rather than a positive determination of security. The assessment was conducted by Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio) and states plainly that the species is known only from type material collected at an imprecise locality, that its taxonomic and distributional limits are unknown, and that no population data, occurrence records in protected areas, or monitoring programmes exist.
Bahia state contains Atlantic Forest drainages that are among the most threatened freshwater systems in Brazil — heavy deforestation, water abstraction, pollution, and dam construction have dramatically altered coastal rivers since Günther's time. Whether H. brevicauda still exists anywhere in those systems cannot be stated with confidence. The priority action identified by the IUCN is targeted field survey and taxonomic revision to establish whether the name applies to a surviving, identifiable population — a task that remains outstanding.