Taxonomy & naming
Hypostomus scaphyceps was described by John Treadwell Nichols in 1919, based on a specimen from Cerqueira Cezar in São Paulo State, Brazil — a locality in the Paranapanema River drainage, itself a major tributary of the Paraná. The Catalog of Fishes (Eschmeyer, CAS) records the valid combination Hypostomus scaphyceps with species id 5178, and no synonyms are listed.
The species epithet refers to head shape: scaphyceps derives from the Greek skaphe (a trough or boat-hull) and keps (head), together suggesting a trough-shaped or deeply concave cranial profile. The significance of this character within Hypostomus — a genus with over 130 valid species — is unclear without reference to a series of adult specimens.
A critical limitation of all downstream literature is that Nichols' holotype is a juvenile measuring approximately 1.5 in standard length. Juvenile Hypostomus are notoriously difficult to assign to species, and osteological and external characters useful for species diagnosis are often incompletely expressed in small fish. No adult material referable to H. scaphyceps has been reported in the primary literature. The species is Not Evaluated by the IUCN Red List.
Morphology
The only confirmed specimen of Hypostomus scaphyceps is the juvenile holotype at approximately 1.5 in SL. FishBase records this as the maximum known length (Ref. 36817) — an unusual situation in which the catalogue entry does not represent an adult maximum but rather the size of the sole known specimen. Adult size is unknown; by comparison with other small-to-mid-sized Paranapanema basin Hypostomus, adults might be expected to reach 6–10 in TL, but this is inference from the genus, not a verified figure for H. scaphyceps.
The epithet scaphyceps implies a distinctive head shape, but without adult material available for examination or redescription, detailed morphological characterisation is not possible. General loricariid body plan — bony scutes, ventral sucker mouth, depressed head and body — applies by familial membership. Data sparse.
Habitat
The type locality, Cerqueira Cezar, lies in the Paranapanema River basin of interior São Paulo State, Brazil. The Paranapanema drains the southern plateau of São Paulo and flows westward to join the Paraná River; it encompasses a range of habitats from rocky headwater streams on the Atlantic plateau to broader, warmer lowland sections in the interior.
No habitat observations beyond the type locality are available for H. scaphyceps. Water chemistry, preferred substrate, depth range, and microhabitat use are all undocumented. The Paranapanema is a moderately warm subtropical river; temperatures in the mid-to-upper 20s °C and near-neutral pH would be typical of the region, but no measurements linked to this species are available. PlanetCatfish notes distribution across the broader La Plata, Paraná, and Paranapanema basins, but this presumably reflects inference from the type locality rather than confirmed records of identified adult specimens. Data sparse.
Feeding
No feeding data specific to H. scaphyceps exists in the literature. As a member of Hypostomus, it would be expected to function as an aufwuchs grazer and biofilm scraper, using the ventral sucker mouth to exploit periphyton, algae, and detritus on hard substrates. Whether this species has any dietary specialisations cannot be determined from available records. Data sparse.
Mating
No information on mating behaviour in H. scaphyceps is available. Cave or crevice defence by males, with odontode development during the breeding season, is the genus-wide pattern in Hypostomus, but nothing specific can be attributed to this taxon. Data sparse.
Breeding
No breeding data — captive or field — exists for H. scaphyceps. Hypostomus species are typically cave-spawners with paternal guarding of adhesive egg clutches, but this cannot be confirmed for the present species from available records. Data sparse.
In the aquarium
Hypostomus scaphyceps is not known from the aquarium trade. Given that the only confirmed specimen is a century-old juvenile holotype and adult appearance is undocumented, positive identification of this species in a retail context would be impossible. No husbandry information is available.
Conservation
Hypostomus scaphyceps has not been evaluated by the IUCN Red List. The combination of a holotype-only record, juvenile source material, and an absence of subsequent collections means that the species' current distribution, abundance, and population trend are entirely unknown. Whether H. scaphyceps occurs in any currently protected section of the Paranapanema basin cannot be determined.
The Paranapanema River has been substantially modified by hydroelectric dams over the past several decades; the basin now hosts one of the highest dam densities of any Brazilian river. The ecological consequences for benthic loricariid communities — which depend on rock and wood substrate, and are sensitive to changes in sediment load and flow regime — may be significant, but cannot be assessed for this species specifically without baseline survey data.