Pareiorhina hyptiorhachis Silva, Roxo & Oliveira 2013

This species can be diagnosed from its congeners, except Pareiorhina carrancas, by having a postdorsal ridge (vs. the absence). It can be distinguished from P. carrancas by having a more elevated postdorsal ridge, 6.7-26.8% of CP depth (vs. 4.47-9.03%). It can be further distinguished from P. cepta by having a naked abdomen (vs. having small plates covered with odontodes irregularly distributed on the abdomen); from P. brachyrhyncha and P. cepta by having unicuspid teeth (vs. teeth with a minute lateral cusp); from P. carrancas and P. rudolphi by having the anterior profile of the head rounded in dorsal view (vs. elliptical) and by having a greater suborbital depth (35.0-40.5% of HL vs. 27.4-34.2% in P. carrancas and 24.5-31.8% in P. rudolphi). This species further differs from its congeners by having head width 100.1-108.6% of HL (vs. 91.7-98.1% in P. brachyrhyncha, 82.9-96.2% in P. carrancas, 83.4-90.5% in P. cepta and 77.8-82.1% in P. rudolphi) (Ref. 93835).

Dorsal soft rays (total): 9; Analsoft rays: 6; Vertebrae: 29

Found in moderate to fast-flowing streams, with a substrate of rocks and sand and margins covered by aquatic vegetation. Occurs in association with loose stones, on the streambed. Syntopic throughout its distributional range with Astyanax sp., Characidium sp., Geophagus brasiliensis, Harttia cf. carvalhoi, Imparfinis sp., Neoplecostomus microps, Trichomycterus cf. alternatus, and Trichomycterus sp. (Ref. 93835).

Found in moderate to fast-flowing streams, with a substrate of rocks and sand and margins covered by aquatic vegetation. Occurs in association with loose stones, on the streambed. Syntopic throughout its distributional range with Astyanax sp., Characidium sp., Geophagus brasiliensis, Harttia cf. carvalhoi, Imparfinis sp., Neoplecostomus microps, Trichomycterus cf. alternatus, and Trichomycterus sp. (Ref. 93835).

Dorsal, lateral, and ventral views of the holotype of Pareiorhina hyptiorhachis.

Pareiorhina hyptiorhachis is a species of catfish in the family Loricariidae. It is native to South America, where it occurs in the basins of the Pomba River and the Paraíba do Sul in Brazil. It is typically found in small streams with moderate to fast flow, margins covered in aquatic vegetation, and a substrate composed of rocks and sand. It is known to occur alongside the species Geophagus brasiliensis and Neoplecostomus microps, as well as members of the genera Astyanax, Characidium, Harttia, Imparfinis, and Trichomycterus. The species reaches 3.9 cm (1.5 in) in standard length.

Morphometric and meristic data are given in Table 1. In lateral view, dorsal profile of body strongly convex from snout tip to distal margin of supraoccipital; straight from supraoccipital to dorsal-fin origin; slightly decreasing to end of caudal peduncle. Ventral surface of body, slightly concave at head portion, straight to convex from posterior end of head to pelvic-fin insertion, and straight but angled to posterior end of caudal peduncle. Snout tip rounded in dorsal view. Nostril small. Trunk and caudal peduncle rectangular in cross-section. Morphometric data for Pareiorhina hyptiorhachis. SD = Standard Deviation, IO = Interorbital, OD = Orbital Diameter, CP = Caudal Peduncle.
Pareiorhina hyptiorhachis n=21 Holotype Range Mean SD Standard length (SL) 33.6 26.6–38.8 31.0 3.0 Percents of Standard length (SL) Predorsal length 44.2 41.5–48.8 44.7 1.6 Preanal length 59.2 56.1–65.9 60.5 2.4 Head length 31.7 28.6–35.5 31.8 1.5 Cleithral width 32.8 30.4–36.9 33.5 1.8 Dorsal-fin unbranched ray length 21.2 20.3–24.1 22.2 1.1 Base of dorsal fin length 15.4 14.3–18.3 16.5 1.1 Thorax length 18.1 15.1–19.6 17.0 1.3 Pectoral-fin unbranched ray length 20.5 20.5–26.0 22.6 1.5 Abdomen length 27.0 22.6–30.1 26.2 1.6 Pelvic-fin unbranched ray length 22.5 17.7–26.6 22.9 2.1 Anal-fin length 15.3 13.7–17.8 15.6 0.9 Ventral unbranched caudal ray 24.9 20.3–30.5 25.2 2.8 Caudal-peduncle depth 9.0 8.3–11.0 9.39 0.7 Postanal length 34.9 31.6–38.1 33.9 1.4 Anal width 15.4 11.3–16.0 14.0 1.5 Percents of Head Length (HL) Head width 103.8 100.1–108.6 103.8 2.6 Head depth 61.7 53.5–62.8 56.9 2.3 Snout length 63.1 58.0–64.7 61.2 1.9 Interorbital width 37.7 34.8–40.7 38.0 1.4 Orbital diameter 11.4 11.1–15.5 12.7 1.6 Suborbital depth 39.2 35.0–40.5 37.3 1.6 Mandibular ramus 18.1 16.0–23.4 19.9 1.9 Other measurements (expressed as percentages) Anal width/cleithral width 47.1 32.0–49.7 42.0 5.1 IO/OD 29.5 21.6–42.1 33.5 4.5 IO/Mandibulary ramus 50.6 44.1–62.5 52.4 5.6 Predorsal length/first ds ray length 47.9 45.7–54.5 49.7 2.6 Postanal length/CP depth 25.8 24.8–31.1 27.6 1.9 Pelvic-fin length/CP depth 40.0 36.0–46.8 41.1 3.0 Ventral unbranched caudal ray/CP depth 36.2 32.1–46.0 37.5 4.3 Postdorsal ridge depth/CP depth 19.0 16.7–26.8 21.5 3.4 Greatest body depth at dorsal-fin origin. Body progressively narrowing posteriorly from cleithrum. Head flat to slightly convex between orbits; superior margin of orbits elevated. Eye small, orbital diameter 11.1–15.5% of HL, situated dorsolaterally just posterior of midpoint of head. Rostral margin of snout with minute, posteriorly-directed odontodes; numerous small odontodes on dorsal portion of head. Opening of swimbladder capsule small. Perforations of compound pterotic distributed on whole bone, greater and more concentrated on its ventral margin; its openings nearly rounded in median region, and irregular along inferior and posterior margins of bone. Lips large; oral disk rounded, papillose; premaxillary teeth 22 (1), 29 (1), 30 (1), 32 (1), 33 (1), 34 (2), 36 (1)*, 37 (2), 38 (1), 39 (2), 40 (2), 42 (2) or 44 (1). Dentary teeth 17 (1), 21 (1), 23 (1), 28 (1), 30 (2), 32 (2)*, 33 (2), 34 (2), 35 (1), 36 (1), 39 (1), or 45 (1). Teeth unicuspid. Maxillary barbel short and free distally. Dorsal-fin rays ii,7; dorsal-fin originating at vertical through posterior end of pelvic-fin base; distal margin slightly convex. Pectoral-fin rays i,6; distal margin slightly convex; unbranched pectoral-fin ray reaching middle of unbranched pelvic-fin ray; unbranched pectoral-fin ray covered with large and pointed odontodes. Pelvic-fin rays i,5; distal margin of fin slightly convex; tip of adpressed pelvic fin almost reaching anal-fin origin; unbranched pelvic-fin ray covered with conspicuously pointed and well-developed, and uniformly distributed odontodes which are larger at ventral portion. Anal-fin rays i,5; distal margin slightly convex. Caudal fin rays i,7-7,i. Adipose fin absent. Caudal fin truncated with ventral unbranched principal ray longer than dorsal ray. Body entirely covered by bony plates, except for ventral surface of head, abdomen and region overlaying swimbladder capsule. Dorsal series of plates 24–26, mid-dorsal 17–21, median perforated plates 24–26, mid-ventral 17–22, and ventral 19–22. Trunk with conspicuous, elongated, postdorsal ridge formed by 13–15 raised, unpaired, median plates; ridge continuous posteriorly with procurrent caudal-fin rays. Head lacking crest. Head and body plates covered with minute, uniformly sized and distributed odontodes. Seven pairs of ribs associated with vertebrae 8–14. Ribs slender and poorly ossified. Total vertebrae 29. Supraorbital sensory canal with four pores; pore s1 located on prenasal plate below nasal plate; pore s3 located on posterior portion of nasal; pore s6+s6 located between frontal plates, on horizontal line through anterior limits of eye; pore s8 located on division between frontals, sphenotic and supraoccipital plates, just above eye. Infraorbital sensory canals with six pores; pore io1 located on anterior portion of first infraorbital; pore io2 located in medial region between first and second infraorbitals; pore io3 located in medial region between second and third infraorbitals; pore io4 located in medial region between third and fourth infraorbitals; pore io5 located in medial region between fourth and fifth infraorbitals and pore io6 located between sixth infraorbital and sphenotic. Preopercular canal with three pores; pore pm2 located on ventral portion of cheek plate, pore pm3 located between cheek plate and preopercle; pore pm4 located between preopercle and compound pterotic. Two postotic pores; pore po2 located just above of branchial slit; pore po3 located in region of overlying opening of swim-bladder capsule.

Pareiorhina hyptiorhachis is known from Rio Pomba and one of its tributaries, the Ribeirão Fernandes, in the municipality of Santa Barbara do Tugúrio, Minas Gerais State, Brazil (Fig. 5). This species inhabits moderate to fast-flowing streams, with a substrate of rocks and sand and margins covered by aquatic vegetation. Specimens were collected in association with loose stones, on the streambed. The new species is syntopic throughout its distribution with Astyanax sp., Characidium sp., Geophagus brasiliensis, Harttia cf. carvalhoi, Imparfinis sp., Neoplecostomus microps, Trichomycterus cf. alternatus, and Trichomycterus sp.