Taxonomy & naming
Oxynoemacheilus longipinnis was described by Brian W. Coad and Theodore T. Nalbant in 2005, one of many stone-loach species named from the region in the wave of Nemacheilidae taxonomy that followed the breakup of the old, catch-all genus Noemacheilus (and its near-synonym Nemacheilus) into a set of narrower, better-defined genera. Oxynoemacheilus is one of the genera that absorbed part of that old assemblage, alongside Schistura, Triplophysa, Barbatula and Paracobitis, and the Catalog of Fishes — the standing authority for valid fish names — currently accepts Oxynoemacheilus longipinnis under this combination.
The family placement is Nemacheilidae, the stone and brook loaches, now recognized as the largest family within the loach superfamily Cobitoidea. It is a family in continual taxonomic motion as regional faunas are revised species by species, and a recently described, narrow-range species such as this one is exactly the kind of taxon still being sorted out — worth flagging here rather than glossing over.
Morphology
Species-level measurements for Oxynoemacheilus longipinnis are not confirmed in the sources available for this profile, so no specific maximum length is given here. What can be said comes from the genus: Oxynoemacheilus species are small, slender, cylindrical stone loaches, typically only a few centimetres long, built low and streamlined to hold position on the bed of a fast stream rather than to swim in open water.
As in other nemacheilids, the skin is effectively naked to the eye — scales, where present, are minute and deeply embedded — which leaves these fish more exposed to medications and water-quality stress than heavily scaled fish. Many members of the family also carry a small erectile spine beneath the eye, a defensive structure shared across the loach superfamily; whether it is prominent in this particular species is not confirmed here, so it is noted as a family trait rather than asserted for O. longipinnis specifically.
Habitat
Oxynoemacheilus is a genus centred on Iran and the surrounding parts of the Middle East and Anatolia, occupying the region's cool-to-warm, clear, fast-flowing streams and rivers — the classic stone-loach habitat of gravel and rubble beds swept by well-oxygenated current. Species in this genus are frequently narrow-range stream endemics, known from a single drainage or even a single watercourse, which is consistent with how sparsely documented O. longipinnis is in the wider literature.
No confirmed, species-specific locality or water-chemistry data for O. longipinnis is available in the sources consulted for this profile. Rather than invent numbers, this profile notes the genus pattern — clear, current-swept, well-oxygenated fresh water, typically cooler than a tropical community tank — and defers to the original 2005 description and any regional ichthyological survey for the specifics of this species' home stream.
Feeding
As a Nemacheilidae stone loach, Oxynoemacheilus longipinnis is presumed — by strong analogy with its genus and family — to be a benthic micro-predator, picking small invertebrates such as insect larvae, worms and tiny crustaceans from among the gravel and stones of its stream bed. This is the near-universal feeding mode across the stone and brook loaches and there is no reason to expect this species differs.
No species-specific dietary study is confirmed in the sources for this profile. In captivity, fish of this genus and habit are generally expected to take small sinking live and frozen foods (bloodworm, daphnia, brine shrimp) readily, with prepared sinking foods accepted less reliably; this is stated as a reasonable inference from the family's known biology, not a confirmed observation of this species.
Mating
No courtship or spawning observations for Oxynoemacheilus longipinnis are confirmed in the sources available here. Sexual dimorphism has not been documented for this species in the material consulted, and no assumption is made about it. Across Nemacheilidae generally, where dimorphism is recorded at all it tends to be subtle — a slightly deeper or more rounded body in ripe females — but this is a family-level generalization, not a statement about this particular species.
Breeding
Stone and brook loaches like Oxynoemacheilus longipinnis are, as a rule, egg-scatterers: ripe adults release eggs over gravel and among stones in fast-flowing water, with no parental care of eggs or fry. That is the family pattern and it is reasonable to extend it to this species, but no confirmed breeding record — captive or wild-observed — exists for O. longipinnis in the sources used here.
Honestly stated, this is a species that is rarely or never bred in the aquarium. Most Oxynoemacheilus species are little-known stream endemics outside specialist and academic circles, and there is no evidence in the available sources of hobbyist spawning success. Anyone keeping this fish should expect to enjoy it as a wild-type stream fish, not to breed it at home.
In the aquarium
Oxynoemacheilus longipinnis is essentially unknown in the mainstream aquarium hobby — it does not appear to have an established care profile on the major hobbyist reference sites, which is itself useful information: this is not a fish to buy expecting a well-trodden care sheet. Anyone who does encounter it, likely as a specialist import, should default to genus-typical stone-loach care: cool-to-moderate, very well-oxygenated, current-swept water over a gravel or fine-stone substrate, since that is the habitat the genus is built for.
As with other nemacheilids, the effectively scaleless skin means caution with medications and copper-based treatments is warranted, dosed gently and watched closely rather than assumed safe at full strength. Given the general absence of confirmed data, a keeper taking this species on should treat it as an experimental, specialist fish and prioritize stable, clean, flowing, well-oxygenated conditions over any specific temperature or hardness figure not confirmed by a primary source.
Conservation
Oxynoemacheilus longipinnis does not appear to have been formally assessed on the IUCN Red List; it is recorded here as Not Evaluated rather than assigned a guessed category. This is a common situation for narrow-range Nemacheilidae species from the Middle East and Iran, many of which are known from very limited material and have not yet been through a Red List assessment.
As with many small, recently described stream endemics in this genus, the general risks — where documented for related species — tend to be habitat-driven: water abstraction, damming, pollution and stream modification in the rivers of Iran and neighbouring countries. No specific conservation study or threat assessment for O. longipinnis itself is confirmed in the sources used for this profile, and none is invented here.