Rhinotocinclus longirostris (Garavello, 1988), new combination

(Fig. 18; Tab. 3)

Parotocinclus longirostris Garavello, 1988:120 (Type-locality: Rio Preto da Eva, Manaus-Itacoatiara highway, km 80, Manaus, [Amazonas, Brazil]. Holotype: MZUSP 36891).

Diagnosis. Rhinotocinclus longirostris is distinguished from R. acuen, R. bockmanni, R. chromodontus, R. dani, R. dinizae, R. hera, R. jumaorum, R. pentakelis, R. marginalis n. sp., and R. loxochelis n. sp. by possessing an adipose fin (vs. adipose fin absent), and by having a Y-shaped light mark from the snout tip to each nostril (Figs. 6A,B; vs. light mark V-shaped or present as two separate lines from snout tip diverging to each nostril). It is distinguished from R. collinsae, R. halbolthi, and R. hardmanni by lacking accessory teeth on both premaxilla and dentary (Figs. 5B,C; vs. accessory teeth present); the odontodes on the ventral surface of first pelvic-fin ray bent and pointing mesially (Fig. 9A; vs. odontodes aligned with main ray axis, Fig. 9B); a triangular dark spot on the anterior portion of the dorsal-fin membrane (Fig. 8B; vs. dorsal-fin spot absent); a Y-shaped light mark from snout tip to nostrils (vs. light mark absent); and a larger orbit, 26.7–31.4% snout length (vs. orbit 18.9–24.6% snout length). Rhinotocinclus longirostris is distinguished from R. britskii and R. kwarup, by having the snout more acutely pointed (Fig. 11B; vs. snout more broadly rounded, Fig. 11A); dark bars on body wider and closer together (Fig. 7B; vs. dark bars on body narrower and more widely spaced, Fig. 7A); and 2–3 plates between the posterior border of the rostral plate and the nostril (Fig. 12A; vs. one plate). Rhinotocinclus longirostris is distinguished from R. variola, R. yaka, R. discolor n. sp., R. isabelae n. sp., and R. pilosus n. sp. by having 4–5 irregular series of middle abdominal plates (vs. 0–2, rarely 3 irregular series); and five dark bars on body (Fig. 7B; vs. four dark bars on body [bars 1+2 or 2+3 fused], Fig. 7C). It is distinguished from R. eppleyi by having more numerous premaxillary, 28–36 (mode 30) and dentary, 27–31 (mode 30) teeth (see Tabs. 1–2, vs. fewer premaxillary (22–30, mode 26) and dentary (21–27, mode 25) teeth).

Geographical distribution. Rhinotocinclus longirostris occurs in tributaries to the central Amazon, including the Madeira and Negro basins, in the states of Amazonas, Rondônia, and Roraima, Brazil (Fig. 15).

Remarks. Rhinotocinclus longirostris, from the central Amazon basin, is most similar and barely distinguishable phenotypically from R. eppleyii, which inhabits the middle Orinoco. The only morphological differences found between these species are the number of oral teeth, as R. eppleyi has 22–30 (mode 26) premaxillary and 21–27 (mode 25) dentary teeth, while R. longirostris has 28–36 (mode 30) premaxillary and 27–31 (mode 30) dentary teeth. These counts are not fully discrete and partially overlap (see Tabs. 1–2). In addition, body proportions also overlap (compare measurements in Tabs. 3–4). Rhinotocinclus longirostris, listed as Parotocinclus longirostris, is currently assessed as Least Concern (LC) in the Brazilian regional assessment by ICMBio (2018) and in the global assessment by IUCN.

Material examined: Rio Amazonas basin, Brazil: Amazonas State: DEPRJ 8484, 4, igarapé Solimõezinho, bacia do rio Unini, Barcelos, 01º39’18”S 62º58’15”W. MZUSP 36891, holotype (measured), MZUSP 36892–36894, 4 paratypes, rio Preto da Eva, km 80 on road from Manaus to Itacoatiara, Manaus, 02°41’55” 59°42’15”W. MZUSP 36895–36898, 4 paratypes, igarape Tarumãzinho, on road from Manaus to Caracaraí, Manaus, 02°40’28”S 60°02’46”W. INPA 15479, 10, igarapé Caititu, rio Uatumã, 01°42’46.1”S 59°41’58”W. INPA 25483, 25 (5 measured), creek on Fazenda Dimona (PDBFF), approx. 80 km N of Manaus, 02º19’45”S 60º04’39”W. INPA 15885, 1 + 1 cs, igarapé Tarumazinho, tributary of rio Tarumã-Açu, on km 28 of road BR-174, 02º43’31”S 60º04’62”W. INPA 30063, 11, rio Cuieiras, Fazenda DIMONA (PDBFF), Manaus, 02º12’44”S 60º03’20”W. INPA 30278, 21 (5 measured), igarapé Ajuricaba, Presidente Figueiredo, 02º07’04”S 59º56’06”W. INPA 33983, 10, igarapé Solimõezinho, tributary to rio Unini, Barcelos, 01º39’18”S 62º58’15”W. INPA 33984, 30, upper rio Unini, ca. 40 km upstream of confluence with rio Preto, Barcelos, 01º41’32”S 64º04’00”W. INPA 33986, 40, rio Preto, ca. 30 km upstream from confluence with rio Unini, Barcelos, approx. 01º47’S 63º56’W. LBP 13234, 1, igarape da Canoa near Presidente Figueiredo, 01º49’41.35”S 60º12’21.02”W. MHNG 2691.052, 1, rio Araca, tributary to rio Negro, approx. 00°11’S 63°11’W. MZUSP 85786, 18 (5 measured) + 3 cs, rio Preto da Eva, ca. 4 km upstream of Rio Preto da Eva town, 02º40’49.2”S 59º43’15.2”W. MZUSP 117500, 1, creek tributary to rio Aripuanã at Apuí, 07°11’10.10”S 59°50’01.39”W. MZUSP 117630, 1, creek tributary to rio Juma between Novo Aripuanã and km 100, Novo Aripuanã, 06°23’57.7”S 60°01’36.25”W. Rondônia State: MCP 35876, 2, rio Preto do Crespo, ca. 13 km N of Rio Crespo, 09º35’56”S 62º52’43”W. MCP 35882, 2 + 1 cs, creek tributary to rio Crespo, ca. 20 km E of highway BR-364 towards Rio Crespo, 09º42’21”S 62º55’38”W. Roraima State: MCP 46076, 2, rio Jauaperi on vicinal road near highway BR-174, ca. 47 km from Jundiá, Rorainópolis, 00º13’55”S 61º03’52”W.