Taxonomy & naming
Parotocinclus bidentatus was described by Gauger and Buckup in 2005 in the journal Neotropical Ichthyology (volume 3, number 4, pages 509–518), in a paper titled 'Two new species of Hypoptopomatinae from the rio Paraíba do Sul basin, with comments on the monophyly of Parotocinclus and the Otothyrini.' The Catalog of Fishes (Eschmeyer, CAS) lists the species under spid 69123 with the authority Gauger & Buckup, 2005.
The species belongs to the subfamily Hypoptopomatinae, the small dwarf-suckermouth lineage of the family Loricariidae. Notably, the description paper itself raised doubts about whether the genus Parotocinclus, as currently constituted, forms a natural (monophyletic) group — a question that remains unsettled and means the generic placement of this and related species may be revised by future work.
Morphology
Parotocinclus bidentatus is a small loricariid reaching about 1.5 in in standard length. Like other members of the subfamily Hypoptopomatinae, it has a depressed, armoured body clad in rows of bony scutes and a ventral suckermouth.
Detailed diagnostic characters were given in the original 2005 description, but beyond the recorded maximum size, granular morphological data for this species are not summarised in the sources available here. No detail on coloration or distinguishing markings is published in the cached material, so none is asserted.
Habitat
The species is endemic to the Rio Paraíba do Sul basin in southeastern Brazil. It is a freshwater, demersal (bottom-associated) fish of tropical waters.
No specific data on water chemistry, temperature, current, or microhabitat for this species are published in the sources available here. Members of the genus are generally facultative air-breathers, an adaptation associated with shallow, sometimes oxygen-poor stream margins.
Feeding
No diet data specific to Parotocinclus bidentatus are published in the sources available here. Hypoptopomatines in general are small grazers that rasp algae, biofilm (aufwuchs), and fine detritus from submerged surfaces, but no feeding study for this species is cited, so its specific diet remains undocumented.
Mating
No data on courtship or mating behaviour for Parotocinclus bidentatus are published in the sources available here.
Breeding
No data on reproduction, spawning mode, clutch size, or parental care for Parotocinclus bidentatus are published in the sources available here.
In the aquarium
Parotocinclus bidentatus is not a regular fixture of the ornamental trade, and no aquarium-husbandry data for this species are published in the sources available here. Its small size and stream-margin origins are consistent with the general care profile of dwarf Hypoptopomatinae, but specific recommendations cannot be made from the available material without speculation.
Conservation
The IUCN Red List assessed Parotocinclus bidentatus as Data Deficient (DD) on 7 November 2018, indicating that there is insufficient information on its distribution, population, and threats to make a reliable assessment of extinction risk. The species is known only from the Rio Paraíba do Sul basin, a heavily populated and industrialised drainage in southeastern Brazil that faces pressures from pollution, water abstraction, and habitat alteration — factors that make targeted survey work a priority for any future reassessment.