Rhinotocinclus britskii ( Boeseman, 1974 ), 2022

Reis, Roberto E. & Lehmann A., Pablo, 2022, A new genus of armored catfish (Siluriformes: Loricariidae) from the Greater Amazon, with a review of the species and description of five new species, Neotropical Ichthyology (e 220002) 20 (2), pp. 1-100 : 19-22

Rhinotocinclus britskii ( Boeseman, 1974) , new combination

(Fig. 14; Tab. 3 )

Parotocinclus britskii Boeseman 1974:267 (Type-locality: Left tributary of Coppename River, 03°51’N 56°55’W, Surinam. Holotype: ZMA 106593).

Parotocinclus amazonensis Garavello, 1977:7 (Type-locality: Ilha Sorubim, Rio Solimões, Amazonas, Brazil. Holotype: MZUSP 10145). NEW SYNONYM.

Parotocinclus aripuanensis Garavello, 1988:122 (Type-locality: Ingazeiro, 20 km upstream of Boca do Rio Canumã, Aripuanã, MT [ Brazil]. Holotype: MZUSP 36899). NEW SYNONYM.

Diagnosis. Rhinotocinclus britskii 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; Figs. 6C,D and Figs. 6E,F, respectively). 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, Fig. 5A); 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 (Figs. 10B,C; vs. dorsal-fin spot absent); a Y-shaped light mark from snout tip to nostrils (vs. Y-shaped light mark absent); and a larger orbit, 27.8–39.0% snout length (vs. orbit 18.9–24.6% snout length). Rhinotocinclus britskii is distinguished from R. eppleyi , R. longirostris , R. polyochrus , R. variola , R. yaka , R. discolor n. sp., R. isabelae n. sp., and R. pilosus n. sp. by having the snout more broadly rounded (Fig. 12B; vs. snout more acutely pointed, Fig. 12A); dark bars on body narrower and more widely spaced (Fig. 7A; vs. dark bars on body wider and closer together, Fig. 7B); and one plate between the posterior border of the rostral plate and the nostril (Fig. 12B; vs. 2–4 plates, Fig. 12A). It is distinguished from R. kwarup by having fewer premaxillary teeth (15–29, mode 23, vs. 28–34, mode 32), and fewer dentary teeth (15–29, mode 20 and 25, vs. 27–33, mode 29; see Tabs. 1–2 ); and by having the color pattern with less broken marks (vs. color pattern with more broken marks, mottled).

Geographical distribution. Rhinotocinclus britskii occurs in most of eastern Greater Amazon, in both Brazilian and Guianas Shields, including the coastal rivers of the Guianas from Amapá in Brazil to the Mazaruni River in Guyana, the Orinoco tributaries Caroni and Cuyuni, and the rio Branco in northern Amazon, as well as the middle and lower portions of the Madeira, Tapajós, Xingu, and Tocantins rivers, in the states of Amazonas, Goiás, Mato Grosso, Pará, Rondônia, and Tocantins in southern Amazon ( Fig. 15 ).

Remarks. Rhinotocinclus britskii is the only species widely distributed among diverse river basins, occupying a large portion of the eastern Greater Amazon, including coastal rivers of the Guianas, the Cuyuni and Caroni rivers of the Orinoco basin, the rio Branco, and the tributaries to the eastern Amazon basin ( Fig. 15 ). Three species names are available from this region, Parotocinclus britskii , P. amazonensis and P. aripuanensis , and populations from several river basins in this region were compared and tested for morphometric distinctness. Some of these population may possess small, subtle differences that overlap when compared basinwide or across basins, and we were unable to morphologically distinguish these populations (see Figs. 16–17 for a comparison). For this reason, both P. amazonensis and P. aripuanensis are herein synonymized with Rhinotocinclus britskii .

The geographic distribution of Rhinotocinclus britskii , widely distributed in rivers draining the Guianas and Brazilian Shields of eastern Greater Amazon, is not uncommon. Other exemples of such pattern are those of the characid Poptella compressa ( Reis, 1989) , Hoplias aimara ( Mattox et al., 2006) , Roeboexodon guianensis ( Lima, Ribeiro, 2011), and Anostomus ternetzi ( Lima, Ribeiro, 2011), which corroborate the hypothesis of evolution and differentiation on the highlands of the continental shields ( Lima, Ribeiro, 2011; Dagosta, de Pinna, 2019). However, the subtle morphometric variation of this species found among river basins might be indicative of undetected biodiversity. For this reason, a wide molecular study of R. britskii , comparing populations across the entire distribution area is in order. Rhinotocinclus britskii , listed as Parotocinclus amazonensis , is currently assessed as Least Concern (LC) in the Brazilian regional assessment by ICMBio (2018).

Material examined. ZMA 106593 , holotype of Parotocinclus britskii (photos examined), left tributary of Coppename River , Suriname, approx. 03°51’N 56°55’W. MZUSP 10145 , holotype of P. amazonensis , meander of rio Solimões at ilha Sorubim , upstream of Coari , Coari, Amazonas, Brazil, approx. 03°53’S 63°21’W. MZUSP 36899 , holotype of P. aripuanensis (measured) , MZUSP 36900-36906 , 7 paratypes (3 measured), Ingazeiro, 20 km upstream of mouth of rio Canumã , Aripuanã, Mato Grosso, Brazil, approx. 10°10’S 59°27’W. Coppename River basin, Suriname: MHNG 2779.046, 124 , MCP 54760, 10 (10 measured), Kwama creek, tributary to Coppename River, Sipaliwini, approx. 04°50’N 56°07’W. MHNG 2780.072, 5 of 12 (2 measured), Gran Tibiti River, tributary to Coppename River, Sipalawini, Suriname, approx. 04°51’N 56°07’W . Essequibo River basin, Guyana: ANSP 179132, 1, Rupununi River, road crossing 5.9 km WSW of village of Sand Creek, Rupununi (Region 9), 02°58’39.54”N 59°33’54.80”W . ANSP 179133, 3, Rupununi River, 3.7 km SSE village of Massara, Rupununi (Region 9), 03°52’3.54”N 59°17’03”W. ANSP 179135, 1, Essequibo River at Kurukupari, Upper Demerara-Berbice, 04°39’33.40”N 58°40’34.89”W . ANSP 179138, 16, MCP 34708, 5 (3 measured), Rupununi River, sand beach and inlet at Karanambo Ranch, Rupununi (Region 9), 03°45’02.47”N 59°18’08.96”W . ANSP 179210, 3, Rupununi River, 4.6 km NW of village of Massara, Rupununi (Region 9), 03°55’16.54”N 59°16’26.46”W. AUM 35721, 1, Essequibo River at Kurukupari, Upper Demerara-Berbice, 04°39’41.36”N 58°40’30.68”W . AUM 35724, 4, Simoni River, 4 sites from 6.6 km SE to 3.2 km W Karanambo, UpperTakutu-Upper Essequibo (03°43’09.01” N 59°15’40.36” W) . AUM 35722, 4, Rupununi River 4.6 km NW Massara, Upper Takutu-Upper Essequibo, 03°55’33.71”N 59°16’49.33”W . AUM 35723, 2, Rupununi River 3.7 km SSE Massara, Upper Takutu-Upper Essequibo, 03°51’44.21”N 59°17’03.80”W . AUM 35725, 20, Rupununi River at Karanambo, Upper Takutu-Upper Essequibo, 03°45’00.14”N 59°18’30.06”W. INHS 49369, 1, Essequibo River at large sandbar and small cataract 31.9 mi SSW of Rockstone, Mazaruni-Potaro, 05°31’39.5”N 58°37’43.6”W . ROM 86161, 20, Rupununi River, in the vicinity of Yupukari-a stretch of river about 8 km in length, Upper Takutu-Upper Essequibo Region 9, 03°34’34.28”N 59°20’36.6”W . ROM 86412, 12, Rupununi River at Dadanawa, Upper TakutuUpper Essequibo (Region 9), 02°49’54.02”W 59°31’41.17”W . Mazaruni River basin, Guyana: ROM 101591, 1, Mazaruni River, main channel, sandy beach with rocks, Cuyuni-Mazaruni, 06°08’46.03”N 60°02’05.75”W . ROM 102068, 5, Mazaruni River, Inaku Creek mouth, CuyuniMazaruni, 06°08’49.81”N 60°01’54.84”W. ROM 102213, 1, Tamakay Creek, Cuyuni-Mazaruni, 06°20’09.96”N 60°17’25.01”W . Río Orinoco basin, Venezuela: ANSP 168171, 13, Río Miamo on Guasipati-El Miamo road ca. 20 km SW of El Miamo. Rio Yuruari/Cuyuni Drainage, Bolivar, 07°37’52.64”N 61°47’57.63”W . ANSP 168172, 14 + 2 cs, Río Botanamo, just beyond Vivero Florestal Intacmaca on road from Tumeremo to Bochinche, Río Cuyuni drainage, Bolivar, approx. 07°23’N 61°13’W. AUM 36607, 21, Río Macaruma, 134 km SE of Cuidad Guiana, 5 km SE of Guasipati, at old bridge just W of main road, Bolívar, 07°26’15.83”N 61°52’31.94”W . INHS 31733, 10 + 2 cs, Río Guanare at El Miamo, Bolivar, 07°38’29”N 61°46’39”W. MCNG 929, 1, rapids in Caño Negro, first tributary to Río Cuyuni upsteam Isla Anacoco, Bolivar, approx. 06°44’N 61°09’W . MCNG 16041, 1, Río Corumo, at bridge of Bochinche road, Bolivar, approx. 07°19’N 61°24’W . MCNG 16476, 13, Río Botanamo, at bridge of Bochinche road, Bolivar, approx. 07°25’N 61°11’W . MCNG 16656, 2, creek at bridge on km 91 of road to Santa Elena, Bolivar, approx. 06°02’N 61°27’W . MCNG 29427, 1, Río Yuruari E of El Manteco, Bolivar, approx. 07°18’N 62°21’W . MCNG 29463, 12 of 44, Río Guanare at balneario El Miamo, NW of Guasipati, Bolivar, 07°38’29”N 61°47’39”W . MCNG 29527, 1, Río Yuruari W of Guasipati near La Pastora, Bolivar, 07°30’14”N 62°07’56”W . MCNG 43374, 2, 50 m downstream bridge San Miguel de Betania, Las Claritas road, Bolivar, 06°17’42”N 61°18’00”W . Rio Branco basin, Guyana: ANSP 179139, 28, MCP 34709, 10 (5 measured), Sauriwau River, Takutu-Branco drainage, at crossing on road from Lethem to Sand Creek, 31.2 km NW Sand Creek Village, Upper Takutu-Upper Essequibo, Region 9, 03°06’41.19”N 59°46’36.43”W . ANSP 179130, 1, Pirara River, tributary to Ireng River, itself a tributary to Takutu River, 3.5 km NNW of Pirara, Upper Takutu-Upper Essequibo, Region 9, 03°38’43.36”N 59°41’21.67”W. ANSP 179131, 5, Yuora River, tributary to Ireng River, itself a tributary to Takutu River, 6.7 km NE of village of Karasabai on road to Tiger Creek village, Upper Takutu-Upper Essequibo, Region 9, 04°04’21.19”N 59°28’59.83”W . ANSP 179134, 1, Moco-Moco River, tributary to Takutu River, below dam at Moco-Moco Hydro Power Station, 18.8 km SE of Lethem, Upper Takutu-Upper Essequibo, Region 9, 03°19’30.31”N 59°41’26.36”W . ANSP 179137, 1, Ireng River, tributary to Takutu River, 6.9 km WSW village of Karasabai, Upper Takutu-Upper Essequibo, Region 9, 04°00’33.77”N 59°35’30.40”W . ANSP 179498, 6, Takutu River, ca. 2.75 km W of Saint Ignatius, Upper Takutu-Upper Essequibo, Region 9, 03°20’26.84”N 59°49’47.24”W . AUM 35730, 37, Sauriwau River, tributaqry to Takutu River, 31.2 km NW village of Sand Creek, Upper TakutuUpper Essequibo, 03°06’51.55”N 59°46’31.58”W . ROM 95997, 1, Katorwau River, downstream crossing, Upper Takutu-Upper Essequibo, Region 9, 02°53’43.14”N 59°51’20.34”W. ROM 96082, 44, Katorwau River, Kodowidpao, Upper Takutu-Upper Essequibo, Region 9, 02°52’29.64”N 59°49’50.22”W . ROM 96223, 30, Takutu River, rapids at shelf of rock, Upper Takutu-Upper Essequibo, Region 9, 02°50’09.49”N 59°59’25.55”W . Rio Branco basin, Roraima, Brazil: MCP 46094, 1, rio Anauzinho on vicinal road to highway BR-210, São Luiz, 01°12’32”N 60°09’15”W . MCP 46147, 1, rio Jauaperi on vicinal road to highway BR-210 between Caroebe and São João da Bahia, 00°48’14”N 59°49’52”W . MCP 46175, 10, rio Jauaperi on vicinal road 5, ca. 10 km from highway BR-210, Caroebe, 00°54’47”N 59°34’23”W . INPA 1641, 26, rio Uraricoera, Boa Vista, approx. 03°28’N 60°49’W . INPA 1649, 18, furo Santa Rosa, rio Uraricoera at cachoeira Tiporena, Boa Vista, approx. 03°18’N 61°23’W . INPA 1863, 8, rio Uraricoera at Beiradão, Boa Vista, approx. 03°26’N 61°08’W . INPA 6064, 18 (2 measured) + 2 cs, rio Mucajaí at cachoeira Paredão II, Mucajaí, approx. 02°52’N 61°16’W. INPA 8147, 13 + 2 cs, igarapé do Arraia, km 114 on road from Boa Vista to Bonfim, 03°21’21.2”N 59°54’12.7”W . INPA 8164, 8, rio Takutu on road from Boa Vista to Bonfim, near market in Bonfim, 03°21’19.9”N 59°49’51.5”W . INPA 12962, 6, igarapé Surrão near mouth of rio Takutu, on road from Boa Vista to Bonfim, 03°18’23.9”N 59°50’53.9”W . INPA 16419, 35 (3 measured) + 2 cs, rio Catrimani at cachoeira Arapari, upstream mouth of rio Arapari, Boa Vista, approx. 01°49’N 62°16’W . LBP 22255, 2, rio Takutu, Bonfim, 03°21’17.3”N 59°54’16.6”W . MCP 46161, 6 (2 measured), igarapé Cocó on vicinal road 3 between Caroebe and Entre Rios, Caroebe, 00°51’22”N 59°37’02”W. MZUSP 117036, 28 of 58 (3 measured), rio Cauame near mouth of igarapé Au-au, rio Branco basin, Boa Vista, 02º56’27”N 61º01’55”W. Amapá coastal rivers, Brazil: ZUEC 16446, 5 of 11, rio Cachorrinho, tributary to rio Amapari, near Cupixi, Porto Grande, Amapá, 00º41’52”N 51º53’25”W . ZUEC 16582, 16 of 35, rio Ariramba, tributary to rio Tartarugalzinho, Tartarugalzinho, Amapá, 01º21’24”N 50º57’04”W . ZUEC 16817, 9 of 19, rio Amapari, Colônia Água Branca, Água Branca do Amapari, Amapá, 00º56’59”N 52º00’23”W . Rio Trombetas basin, Brazil: MZUSP 15839, 1, beach on rio Trombetas upstrem mouth of lago Jacaré, Trombetas Biological Reserve, Oriximiná, Pará, approx. 01º21’S 56º52’W . Rio Tapajós basin, Brazil: CPUFMT 1451, 30 (3 measured), rio Teles Pires upstream from Sete Quedas rapids, Paranaíta, Mato Grosso, 09°19’00.1”S 56°46’56.7”W . LBP 22254, 3, igarapé Urubutu near Itaituba, Pará, 04°46’10”S 56°46’46”W. LIRP 7442, 1 (measured), rio Jamanxim at cachoeira da Fazenda, Morais de Almeida district, Itaituba, Pará, 06°21’07”S 55°41’06”W . LIRP 7443, 3 + 1 cs, MCP 47078, 2, rio Jamanxim at cachoeira da Fazenda, Morais de Almeida district, Itaituba, Pará, 06°21’07”S 55°41’06”W . LIRP 7444, 5 + 1 cs, rio Jamanxin at first rapids, Novo Progresso, Pará, 07°06’43”S 55°27’17”W . MCP 47077 (formerly LIRP 7444), 5, rio Jamanxim at first rapids, Novo Progresso, Pará, 07°06’43”S 55°27’17”W. INPA 6674, 4, rio Jamanxim at ilha Terra Preta, Trairão, Pará, approx. 05°27’S 55°53’W . INPA 35522, 10 (3 measured), creek on left margin of Sete Quedas rapids on rio Teles Pires, Paranaíta, Mato Grosso, 09°18’58”S 56°47’38”W . INPA 29103, 328 (4 measured), rio Juruena near Salto Augusto, Cotriguaçu, Mato Grosso, approx. 09°16’S 58°38’W. MCP 47684, 30 (5 measured), rio Juruena near Salto Augusto, Mato Grosso, 08°53’20”S 58°33’30”W . MCP 47977, 1 (measured), igarapé Santa Úrsula, rio Juruena basin, Apuí, Amazonas, 08°31’39”S 58°25’27”W. MCP 51603, 1, igarapé tributary to rio Taburari on road BR-163 between Trairão and Caracol, Trairão, Pará, 04°53’38.6”S 56°10’43.8”W. MCP 53608, 1, igarapé tributary to rio Taburari on road BR-163 between Trairão and Caracol, Trairão, Pará, 04°53’38.6”S 56°10’43.8”W . MZUSP 96096, 40 of 68, creek on left bank of rio Teles Pires, Jacareacanga, Pará, 09°18’26”S 56°47’25”W. MZUSP 99254, 11 (3 measured), rio Apiacás near mouth, Apiacás, Mato Grosso, 09°11’36”S 57°04’02”W. Rio Curuá-Una basin, Brazil : MCP 54749, 1, rio Tutuí on Transamazon road ca. 20 km E of Placas, Uruará, Pará, 03°51’33.8”S 54°03’40.5”W. Rio Madeira basin, Brazil: INPA 837, 3, rio Preto do Candeias, Costa Marques, Rondônia, approx. 09°20’S 63°33’W. INPA 1134, 2, igarapé Vertente, upper rio Formoso, serra Pacaás Novos, Ariquêmes, Rondônia, approx. 10°18’S 64°30’W . INPA 1143, 7, igarapé Boa Vista at km 54 of road BR-421 from Ariquêmes to Campo Novo, Ariquêmes, Rondônia, approx. 10°19’S 63°20’W . INPA 4590, 10, rio Machado, Cururu, Costa Marques, Rondônia, approx. 08°21’S 62°42’W . INPA 32983, 73 (6 measured), igarapé Bom Jesus, right margin tributary to rio Guariba at RESEX Guariba, Apuí, Amazonas, 08°40’16”S 60°24’30”W. LBP 10981, 36, rio Lajeado, Guajará-Mirim, Rondônia, 10°26’23.5”S 65°20’34.1”W . MCP 35879, 54 (4 measured) + 4 cs, igarapé Bananeiras on road BR-425 N of Guajará-Mirim and ca. 110 km S of road BR-364, Guajará-Mirim, Rondônia, 10°38’28”S 65°17’34”W . MCP 35883, 1, rio Branco, ca. 10 km N of Ariquemes on road BR-364, Ariquemes, Rondônia, 09°50’40”S 63°03’35”W. MCP 35884, 1, creek tributary to rio Preto do Crespo ca. 27 km E of road BR-364, Rio Crespo, Rondônia, 09°42’21”S 62°55’38”W . MCP 47128, 10 (4 measured), igarapé Karipuna downstream from rapids, Jaci-Paraná, Rondônia, 09°10’26”S 64°39’39”W. MCP 47130, 3 (2 measured), lago Três Praias on rio Jaci-Paraná, Jaci-Paraná, Rondônia, 09°27’17”S 64°25’03”W. NUP 6763, 1 (measured), creek tributary to igarapé Guaribal, rio Madeira basin, Aripuanã, Mato Grosso, 10°04’47”S 59°31’04”W. NUP 7654, 1 (measured), creek tributary to rio Praia Grande, rio Madeira basin, Aripuanã, Mato Grosso, 10°02’43”S 59°20’19”W . NUP 8550, 2 (measured), creek tributary to igarapé Guaribal, rio Madeira basin, Aripuanã, Mato Grosso, 10°04’14”S 59°30’11”W. Rio Xingu basin, Altamira, Pará State, Brazil: MCP 48608 (formerly ANSP 199559), 5 (1 measured), rio Xingu, ca. 44 km SW of Altamira, 03°36’29.3”S 52°20’57.2”W. NUP 19609, 3 (3 measured), rio Três de Maio, tributary to rio Curuá, rio Xingu basin, 08°38’53.7”S 55°01’42.55”W . INPA 30943, 1, ROM 112206, 2 tissue samples, rio Iriri at Barrinha, 04°09’05”S 53°23’28”W. INPA 30944, 4, rio Iriri, Barrinha, rapids in middle of canal, 04°09’05”S 53°23’28”W . INPA 31120, 4, rio Iriri, above mouth of rio Novo, 04°28’11”S 53°41’38”W. MZUSP 111561, 13 (4 measured), black water creek tributary to rio Xingu near cachoeira do Espelho, 03°42’32”S 52°27’11”W . MZUSP 117156, 3 (2 measured), igarapé Babaquara, tributary to rio Xingu near ilha Babaquara, 03°24’42”S 52°12’32”W. Rio Araguaia basin, Brazil: LBP 12274, 47 (7 measured), ribeirão Insula, rio das Mortes basin, Barra do Garças, Mato Grosso, 15°29’57.3”S 52°12’10”W . MCP 40477, 3, córrego Pium, on road BR-158 ca. 22 km S of Posto da Mata, Posto da Mata, Mato Grosso (11°53’58” S 51°39’26” W) . MCP 40576, 1, rio Preto on road BR-158 ca. 72 km S of Porto Alegre do Norte, Mato Grosso, 11°27’47”S 51°40’42”W . MCP 40788, 21 (1 measured), rio Paciguara on road BR- 158, 2 km N of Confresa, Confresa, Mato Grosso, 10°37’34”S 51°32’51”W . MCP 41427, 2 (measured), rio Piranhas near mouth of córrego das Pedras, Piranhas, Goiás, 16°32’03”S 51°49’58”W. MCP 43740, 4 (1 measured), rio Piranhas near mouth of córrego das Pedras, Piranhas, Goiás, 16°32’03”S 51°49’58”W . MHNG 2550.60, 1, rio Araguaia at waterfall between São João [do Araguaia] and São Bento [do Tocantins], Pará, approx. 5°42’S 48°10’W . MZUEL 7698, 2, rio Taquaral, Barra do Garças, Mato Grosso, 15°40’41.4”S 52°17’52.3”W . MZUEL 7699, 14, rio Corrente, Barra do Garças, Mato Grosso, 15°29’56.9”S 52°12’10.5”W . MZUEL 7700, 11, rio Corrente, Barra do Garças, Mato Grosso, 15°29’56.9”S 52°12’10.5”W . MZUEL 7701, 5, creek tributary to rio Insula, Barra do Garças, Mato Grosso, 15°34’19.7”S 52°13’25.6”W. MZUEL 7702, 5, rio Corrente, Barra do Garças, Mato Grosso, 15°29’56.9”S 52°12’10.5”W . MZUEL 7703, 5, córrego Fundo, Barra do Garças, Mato Grosso (15°51’32.2” S 52°19’01.0” W) . MZUEL 7704, 5 rio Corrente, Barra do Garças, Mato Grosso (15°29’56.9” S 52°12’10.5” W). MZUSP 105578, 5, creek tributary to rio Tapirapé, upstream from Bacaba Base of Tapirapé Biological Reserve, Marabá, Pará, 05°36’54”S 50°24’46”W . MZUSP 52162, 43 of 93 (1 measured), rio Água Fria at fazenda Praia Alta 2, on road TO-181 from Araguaçú to Barreira do Pequi, 27 km N of Araguaçú, Tocantins, approx. 12°43’S 49°55’W. MZUSP 89332, 24, córrego Pitomba, tributary to rio Crixás-Mirim at road GO-336, ca. 5 km S of Nova Crixás, Goiás, 14°08’35”S 50°20’13”W. NUP 9733, 1, rio Araguaia between Aragominas, Tocantins and Piçarras, Pará, 06°43’22.62”S 48°46’55.46”W. NUP 19114, 4, córrego Grande, tributary to rio Araguaia, Barra do Garças, Mato Grosso, 15°44’31.04”S 52°05’37.75”W. ZUEC 7422, 14, rio Itacaiúnas, Serra dos Carajás, Igarapé Azul, Parauapebas, Pará, Brasil, 06º04’03”S 49º54’08”W. Rio Tocantins basin, Brazil : INPA 6066, 2, igarapé Canoal, tributary to rio Tocantins, Breu Branco, Pará, approx. 03°45’S 49°33’W . MZUSP 103111, 1 (measured), rio Manuel Alves da Natividade at Porto Alegre do Tocantins, Tocantins, 11°36’41”S 47°02’39”W. MZUSP 106562, 4 (2 measured), rio Pacu near Racha Placa, Mozantinópolis, Canaã dos Carajás, Pará, 06°26’44”S 50°12’50” W.

Figures

FIGURE 15 | Geographical distribution of Rhinotocinclus species of the R. britskii group in central and northwestern South America. Rhinotocinclus britskii (white dots); R. discolor n. sp. (purple dots); R. eppleyi (orange dots); R. isabelae n. sp. (pink dots); R. kwarup (red dots); R. longirostris (blue dots); R. pilosus n. sp. (yellow dots); R. polyochrus (cyan dot); R. variola (black dots); R. yaka (light green dots). T = Type-locality; T1 = type-locality of Parotocinclus britskii, T2 = type-locality of P. amazonensis, T3 = type-locality of P. aripuanensis.

FIGURE 16 | Biplot of first and second Principal Components of morphometric proportions of standard length or head length in populations of Rhinotocinclus bristskii. Percent of variation included in PC1 is 23% and in PC2 is 17%. Head length and prepelvic distance loaded more strongly positively and head depth and interorbital distance loaded more strongly negatively on PC1. Head length and lower caudal-fin principal ray loaded more strongly positively and snout length loaded more strongly negatively on PC2.

FIGURE 17 | Box-plots of morphometric variation in populations of Rhinotocinclus bristskii as percents of standard length (A–O) or head length (P–T). A. Body depth; B. Predosal distance; C. Prepelvic distance; D. Preanal distance; E. Preadipose distance; F. Dorsal-fin spine length; G. Anal-fin unbranched ray length; H. Adipose-fin spine length; I. Pectoral-fin spine length; J. Caudal peduncle depth; K. Dorsaladipose fin distance: L. Dorsal-fin base length; M. Lower caudal-fin principal ray; N. Cleithral width; O. Head length; P. Head depth; Q. Interorbital distance; R. Orbital horizontal diameter; S. Snout length; T. Internarial distance. Number of individuals examined by geographic region: Tocantins (3), Araguaia (12), Xingu (10), Juruena (10), Tapajós (10), Madeira (10), Aripuanã (14), Branco (8), Uraricoera (10), Mazaruni (7), Essequibo (7), Coppename (12), and Amapá (8).