Taxonomy & naming
Aspidoras brunneus was described by the Dutch ichthyologists Han Nijssen and Isaäc Isbrücker in 1976, in their first comprehensive review of the genus Aspidoras, from material taken in the Serra do Roncador region of Mato Grosso State, Brazil. Aspidoras Ihering, 1907 is a small genus of armoured catfishes (family Callichthyidae, subfamily Corydoradinae) restricted to Brazil and closely allied to the familiar Corydoras of the aquarium trade; the two genera are told apart chiefly by skull anatomy, Aspidoras retaining two cranial fontanels where Corydoras has one.
The large 2024 revision of the Corydoradinae by Dias, Tencatt and colleagues (DOI 10.1093/zoolinnean/zlae053) split the swollen genus Corydoras into several lineages (Brochis, Hoplisoma, Gastrodermus, Osteogaster and others), but Aspidoras was already recognised as its own genus and was retained intact — so the bronze-striped Roncador fish stays Aspidoras brunneus, and Catalog of Fishes (Eschmeyer, CAS) lists it as a valid species under that name. A detailed taxonomic revision of the genus by Tencatt and co-authors (2021) could add little to the original account: no recent or well-preserved specimens have ever been recovered, so the six 1970s types remain the only material known.
Morphology
This is a tiny catfish even by corydoradine standards: the holotype measures barely 1 in in standard length, and no specimen exceeds about 1 in SL, making it one of the smallest of the armoured catfishes. Like all Aspidoras it is clad in two rows of overlapping bony plates (scutes) rather than scales, carries three pairs of barbels around a small downturned mouth, and bears stiff leading spines in the dorsal and pectoral fins.
What sets A. brunneus apart from every other member of the genus is its colour pattern: a wide, longitudinal, conspicuous dark-brown stripe runs along the dorsal portion of the flank, a marking found in no congener (the Latin brunneus means 'brown', for exactly this feature). A second, more technical distinction is that its nuchal plate — the bony plate behind the head — is entirely buried under a thick layer of skin, whereas in most relatives at least its posterior edge is exposed. Beyond these traits the species is poorly characterised, because the surviving type specimens are in poor condition.
Habitat
Aspidoras brunneus is known only from its type locality, given in the original description as 'km 125 of the road Chavantina–Casximba' — that is, the Xavantina–Cachimbo road across the Serra do Roncador in Mato Grosso. The genus as a whole inhabits small, clear to tan-coloured forest and savanna streams over sand and leaf litter, and this species is presumed to live in the same kind of shallow, flowing headwater habitat.
The maddening complication is that the type locality straddles a watershed: tributaries of both the rio Araguaia (Tocantins system) and the rio Xingu cross or run close to that stretch of road, so the basin from which the species was actually taken cannot be established with confidence. Different authors have variously assigned it to the Araguaia or to the Xingu, and the question remains open. Because no fresh material has been collected, nothing direct is recorded about its preferred temperatures, pH or water chemistry; the figures used by aquarists are inferred from the soft, warm waters typical of the region rather than measured for this fish.
Feeding
No feeding observations exist for Aspidoras brunneus specifically. Like other members of the genus and the broader Corydoradinae, it is expected to be a benthic micro-omnivore, sifting fine sand and leaf litter with its barbels for small invertebrates, insect larvae, microcrustaceans and organic detritus, and expelling cleaned substrate through the gill openings. Its very small size suggests a diet skewed toward correspondingly tiny prey. This account is by analogy with its relatives; the species itself has never been studied alive in any detail.
Mating
There are no records of courtship or spawning for Aspidoras brunneus. Aspidoras, like Corydoras, are egg-laying shoalers with no pair bond, and where breeding has been observed in the genus it follows the corydoradine pattern: a receptive female cleans a surface, males become active around her, and eggs are fertilised and then clasped in a pelvic-fin basket and pressed onto the chosen site a few at a time. Whether A. brunneus conforms to this is unconfirmed and, given that the species has not been seen alive in decades, untested.
Breeding
Nothing is documented about the reproduction of this species — clutch size, egg development, fry growth and triggers are all unknown. Other small Aspidoras that have been bred in aquaria lay modest numbers of adhesive eggs that receive no parental care, with hatching in a few days and free-swimming fry taking infusoria and then micro-foods. Any expectation for A. brunneus is purely an extrapolation from those relatives; the species is not in the aquarium trade and has no captive-breeding history.
In the aquarium
Aspidoras brunneus is effectively unknown to the hobby. It has not entered the ornamental trade, and with the only known specimens being a handful of decades-old museum types, there is no body of husbandry experience to draw on. Were it ever collected and maintained, it would presumably need what its small congeners need: a group of six or more (these are shoaling fish that fail when kept singly), a soft sand substrate to protect the delicate barbels, gentle well-oxygenated flow, warm water in the low-to-mid 20s Celsius, and peaceful tankmates small enough not to bully a sub-2-centimetre catfish. For now, though, those are recommendations for the genus, not tested guidance for this particular fish.
Conservation
Aspidoras brunneus carries a published IUCN Red List status of Least Concern (assessed in 2018). That label sits awkwardly with what is actually known of the fish: it is recorded only from a single, geographically ambiguous type locality, it is represented by just six aged specimens, and two dedicated 2016 expeditions to the Serra do Roncador — together with a search of a regional university collection — failed to find a single individual, turning up only the commoner A. albater and A. poecilus instead. On that evidence the authors of the 2021 generic revision argued the species is better regarded as Data Deficient, the honest verdict for a fish whose basin, habitat and even continued existence are uncertain. Whatever its formal listing, the Serra do Roncador region shows heavy signs of human impact, and a narrow-range endemic known from so little material would be inherently vulnerable.