Taxonomy & naming
Hypostomus khimaera was formally described in 2014 by Tencatt, Zawadzki, and Froehlich in a paper that simultaneously introduced a second new species and redescribed H. cochliodon Kner, 1854 — one of the older benchmarks of the group. The work appeared in Neotropical Ichthyology volume 12, number 3 (pages 585–602). The Catalog of Fishes (Eschmeyer, CAS; genus id 553, species id 73474) records the combination as valid with no synonyms.
The species belongs to the Hypostomus cochliodon group, a lineage within the subfamily Hypostominae united by distinctive dentition and jaw angle characters. Within that group, H. khimaera occupies a somewhat isolated position: it shares the general profile of cochliodon-group members yet departs from each in ways that initially confounded its placement. It differs from H. basilisko by its moderately (rather than highly) developed lateral keels and a vertebral count of 28 (versus 27). It differs from H. cochliodon itself by possessing 12–27 teeth — considerably more than the 7–9 typical of that species — by having the opercle externalized, and again by the vertebral count (28 vs. 29).
A further anatomical distinction separates H. khimaera from all other members of the group: the metapterygoid and hyomandibula are in direct contact, with no notch between them — the opposite condition from its relatives. The dentary angle at which the two halves of the lower jaw meet is strongly acute, less than 80°, which contributes to the chimeric aspect of the animal's morphology.
Morphology
Adults reach up to 6.5 in standard length (SL), a moderate size within Hypostomus. The body plan is elongated and fully plated in the typical loricariid fashion, with overlapping bony scutes covering the flanks and head. The dorsal fin has 2 spines and 7 soft rays; the anal fin bears 5 soft rays.
Coloration is the feature most immediately striking: the ground tone is a dark tan to brownish background crossed by a conspicuous pale or tan stripe running along the flank, and the body and fins are marked with discrete dark spots. This patterned appearance sharply distinguishes H. khimaera from its cochliodon-group relatives, most of which lack such bold markings. The absence of a notch between the metapterygoid and hyomandibula — visible only by dissection or clearing-and-staining preparations — is the most reliable internal character for identification.
Dentition is numerous relative to the group (12–27 teeth counted on the relevant bones), and the dentaries meet at an angle that is more acute than in related species, giving the lower jaw a notably angled profile. The opercle is externalized rather than hidden beneath soft tissue, another feature distinguishing H. khimaera from H. cochliodon.
Habitat
Hypostomus khimaera is known from the Rio Paraguay basin in Mato Grosso State, Brazil. Collection localities include the Cuiabá, Coxipó, Tucavaca, and upper Paraguay drainages, as well as the rio Aquidauana basin, and the type locality — córrego Salobo near Porto Estrela, Serra das Araras — at coordinates 15°39'03"S, 57°12'54"W.
Field observations describe the species as more commonly found in small streams than in the main river channels, and it is often collected along the margins of deeper sites where the substrate is sandy. It was recorded as syntopic with H. cochliodon at several localities, indicating the two species can share habitat at fine spatial scales. The Rio Paraguay system is a warm tropical lowland drainage with seasonal flood pulses; the streams H. khimaera occupies are characteristically clear to lightly turbid, with sandy to soft substrates along the margins and more consolidated substrate toward the centre.
Like other members of the genus, H. khimaera is considered a facultative air-breather, capable of supplementing gill respiration by gulping atmospheric air — an adaptation useful during periods of low dissolved oxygen that can accompany the warm, shallow conditions of marginal stream habitats.
Feeding
No specific dietary studies have been published for H. khimaera. Members of the genus Hypostomus are typically aufwuchs grazers and detritivores, using their ventrally positioned sucker mouth to rasp algae, biofilm, and fine organic matter from substrate surfaces including rock, wood, and sediment. The Hypostomus cochliodon group shows some tendency toward harder food items, and the relatively numerous teeth of H. khimaera suggest it can process a range of material.
In a community aquarium, Hypostomus species of this size generally accept algae-based sinking wafers, spirulina tablets, and blanched vegetables such as courgette, cucumber, and sweet potato. Driftwood should be available both for grazing the associated biofilm and as structure. Supplementary protein in the form of sinking pellets or occasional frozen foods can be offered but should not dominate the diet.
Mating
No reproductive observations specific to H. khimaera are on record. The Hypostomus genus is broadly consistent in reproductive strategy: males typically claim and defend cavities — crevices among rocks or sunken wood — and attract females to spawn within them. Sexual dimorphism in the genus often takes the form of enlarged interopercular odontodes (bristle-like structures on the cheek) in breeding males, along with generally more pronounced odontodes on the pectoral spines and body flanks.
In the absence of species-specific data, the general pattern of male territorial defence and cave preference is the best guide. Providing suitable cave structures — ceramic tubes, hollow wood sections, or stacked flat stones — in any captive setting would be necessary for natural behaviour to proceed.
Breeding
No confirmed breeding reports for Hypostomus khimaera have been published or widely documented in the hobby literature. The species has not established itself as a hobbyist fish with a known captive breeding history. Based on genus-level biology, it would be expected to be a cave-spawner with paternal brood care, with the male guarding and fanning the egg clutch until hatching — the standard Hypostomus reproductive mode.
Given the species' moderate size (up to 6.5 in SL), any serious breeding attempt would require a substantial aquarium with appropriate cave structures and stable, warm water conditions approximating the warm Paraguayan lowland climate.
In the aquarium
Hypostomus khimaera has not become established in the ornamental trade and is not commonly encountered by hobbyists. Its natural range in the Rio Paraguay basin of Mato Grosso State is not a primary collection region for the aquarium trade, and the species lacks an L-number or common name that would facilitate hobbyist recognition.
As a mid-sized Hypostomus reaching 6.5 in SL (total length would be somewhat greater), any aquarium housing this species would need to be correspondingly large — a minimum of 55 US gal is a reasonable baseline for a single individual, with well-oxygenated water, a sandy substrate along at least part of the base, and ample hiding structure. Water parameters reflecting the tropical lowland Paraguay basin would apply: warm temperatures (75–82 °F), near-neutral pH, and moderate water hardness.
Biofilm and algae grazing on surface structures is important for this and related species; a mix of smooth stones, driftwood with associated biofilm, and occasional vegetable supplements would form the dietary core. The species' co-occurrence with H. cochliodon in the wild does not necessarily mean the two would be compatible in a confined aquarium; intraspecific and closely related Hypostomus can be aggressively territorial in small spaces.
Conservation
Hypostomus khimaera has not been assessed by the IUCN Red List and carries a status of Not Evaluated. The species was described in 2014 from a relatively restricted range within the upper Rio Paraguay basin — the Cuiabá, Coxipó, Tucavaca, and Aquidauana sub-basins in Mato Grosso State, Brazil — and the full extent of its distribution remains incompletely known.
The upper Paraguay basin, while not as heavily degraded as some Brazilian river systems, faces pressure from agricultural expansion, sedimentation associated with soy and cattle production across the Cerrado and Pantanal margins, and altered hydrology from small dams and water diversions. For a species with a moderate documented range and association with marginal small-stream habitats, the cumulative effects of basin-level land-use change could represent a meaningful pressure on population connectivity. No formal population data exist. A future IUCN assessment would benefit from additional field surveys across its known sub-basins.