Rhinotocinclus chromodontus (Britski & Garavello, 2007), new combination

(Fig. 42; Tab. 9)

Hisonotus chromodontus Bristski & Garavello, 2007:414 (Type-locality: Brazil: Mato Grosso State: Diamantino, creek number 1, tributary of Rio Preto, on road to São Francisco, Rio Arinos drainage, ca. 14°18’S 56°20’W. Holotype: MZUSP 45355).

Diagnosis. Rhinotocinclus chromodontus is distinguished from congeners, except R. acuen, R. jumaorum, and R. dinizae, by having the dominant color pattern formed by a dark stripe from the snout tip, through the eye and extending to end of caudal peduncle (Fig. 7E; vs. dominant color pattern formed by dark bars separated and distinct, or dark bars wide and partially coalesced or closed together), and by having a V-shaped light mark from the snout tip to each nostril (Figs. 6C,D; vs. light mark absent, Y-shaped or present as two separate lines from snout tip diverging to each nostril). It is also distinguished from congeners, except R. acuen, R. hera, R. jumaorum, and R. dinizae, by lacking an adipose fin or platelets at the adipose-fin position (vs. adipose fin or platelets present). Rhinotocinclus chromodontus is distinguished from R. acuen, R. jumaorum, and R. dinizae by having the caudal fin mostly brown, with two hyaline spots on upper and lower lobes (Fig. 42; vs. caudal fin with a dark blotch at base and two irregular dark bands), and from R. acuen, R. dinizae, R. hera by having the oral teeth reddish brown (vs. teeth light ochre). It is further distinguished from R. acuen, R. dinizae, R. hera, and R. jumaorum by the dorsal- and pectoral-fin spines homogeneously dusky (vs. spines with 2–3 dark dots).

Geographical distribution. Rhinotocinclus chromodontus occurs in the upper rio Tapajós basin, in the state of Mato Grosso (Fig. 43).

Remarks. Two species of Hisonotus were described by Britski, Garavello (2007), H. chromodontus and H. luteofrenatus, from the upper rio Tapajós, being thus compared to other Hisonotus species. Hisonotus luteofrenatus has already been transferred to Curculionichthys and H. chromodontus is herein being transferred to Rhinotocinclus . We take this opportunity to mention that figures 3a and b are interchanged in Britski, Garavello (2007), as can be easily noticed by the single rostral plate of Rhinotocinclus (compared to the paired rostral plate of Curculionichthys) and the posteriorly projected canal cheek plate (compared to the mesially projected plate of Curculionichthys). Rhinotocinclus chromodontus, listed as Hisonotus chromodontus, is currently assessed as Least Concern (LC) in the Brazilian regional assessment by ICMBio (2018).

Material examined. Brazil, Mato Grosso State, Rio Tapajós basin: MZUSP 45255, holotype (measured), riacho Três, tributary to rio Preto on road to São Francisco, Diamantino, approx. 14°16’S 56°19’W . MCP 37636, 5 paratypes (4 measured), rio Sumidouro Grande, tributary to rio Arinos on farm Arrossensal, Nortelândia, approx. 14°05’S 56°45’W . AUM 73895, 10, INPA 59666, 10, MCP 35873, 150+ 10 cs, MHNG 2787.079, 10, ROM 111487, 10, rio Sauê-Uiná below dam on road BR-364 towards Sapezal, Sapezal, 13°32’22”S 58°50’48”W. MCP 32648, 3, creek on road MT-338, ca. 158 km N of Tapurah, Simione, 11°42’13”S 56°56’17”W. MCP 32649, 28, creek on road MT-338, ca. 33 km N of Tapurah, Tapurah, 12°29’46”S 56°40’43”W . MCP 32650, 9, creek ca. 20 km NW of São José do Rio Claro, on road to Nova Maringá, São José do Rio Claro, 13°20’29”S 56°51’07”W. MCP 32651, 6 (3 measured), creek on road MT-010, from Diamantino to São José do Rio Claro, 96 km NW of Diamantino, São José do Rio Claro, 13°37’05”S 56°34’27”W . MCP 32652, 6, ribeirão Macuco on road BR-163, ca. 74 km N of Sinop, Sinop, 11°17’35”S 55°19’10”W. MCP 32653, 1, rio Roquete on road BR-163 ca. 45 km N of Sinop, Sinop, 11°32’20”S 55°23’35”W . MCP 32654, 16, creek on road MT-338, ca. 89 km N of Tapurah, Tapurah, 12°01’49”S 56°33’59”W . MCP 32655, 2, creek on road from road MT-010 to Nova Mutum, ca. 11 km W from ferry crossing rio Arinos, São José do Rio Claro, 13°37’23”S 56°29’18”W . MCP 32656, 2, creek ca. 22 km NW of São José do Rio Claro, on road to Nova Maringá, São José do Rio Claro, 13°19’24”S 56°51’22”W. MCP 32657, 1, creek on road MT-338, ca. 46 km N of Tapurah, Tapurah, 12°23’14”S 56°41’54”W . MCP 32658, 1, creek on road MT-338, ca. 131 km N of Tapurah, Simione, 11°47’40”S 56°44’09”W . MCP 32659, 4, creek on farm Esplanada Arinos, on road from road MT-010 and ferry to Nova Mutum, São José do Rio Claro, 13°36’31”S 56°32’10”W . MCP 32660, 134 (3 measured), igarapé Ribeirão Preto, on road MT-338, ca. 26 km ESE of Porto dos Gaúchos, Porto dos Gaúchos, 11°39’27”S 57°12’07”W . MCP 32674, 1, creek tributary to rio Caibi on road MT-140 from Santa Carmen to Vera, Vera, 12°10’40”S 55°20’23”W . MCP 32675, 62 + 5 cs, rio Celeste ca. 9 km W of Nova Ubiratã, on road to Sorriso, Nova Ubiratã, 13°03’08”S 55°21’13”W . MCP 32677, 5 + 1 cs, creek tributary to rio Celeste ca. 47 km NW of Nova Ubiratã on road to Sorriso, Sorriso, 12°45’47”S 55°31’05”W . MCP 32678, 19 + 2 cs, córrego Maria (or Quinze), on road BR-163 ca. 23 km N of Sinop, Sinop, 11°43’16”S 55°27’33”W . MCP 35871, 1, córrego Água Quente, on road from Sapezal to rio Papagaio, Sapezal, 13°32’25”S 58°43’32”W. MCP 44413, 16, creek on road MT-235 from Nova Mutum to Santa Rita do Trivelato, Nova Mutum, 13°48’55”S 56°02’39”W. MCP 44419, 2, córrego Conguinha on road MT-235, from Nova Mutum to Santa Rita do Trivelato, Nova Mutum, 13°47’44”S 55°53’25”W . MCP 44447, 10, rio Criquiri, ca. 8 km from Nova Mutum, Nova Mutum, 13°48’11”S 56°09’23”W . MCP 44473, 2, rio dos Patos on road MT-235 from Nova Mutum to Santa Rita do Trivelato, Nova Mutum, 13°48’00”S 56°01’36”W. MZUEL 7882, 18, córrego Água Quente, tributary to rio Papagaio, rio Juruena basin, Sapezal, 13°32’25.5”S 58°43’34.8”W . MZUEL 9067, 7, córrego Santa Cruz, tributary to rio Papagaio, rio Juruena basin, Brasnorte, 12°48’21.7”S 58°09’21.5”W. MZUEL 9068, 10, rio do Calor, tributary to rio Papagaio, rio Juruena basin, Sapezal, 13°02’57.1”S 58°39’15.7”W . MZUEL 9070, 3, tributary to rio Norato (or Honorato), itself a tributary to rio do Sangue, rio Juruena basin, ca. 7 km S of Brasnorte, 12°11’12.9”S 57°59’33.3”W . MZUEL 9073, 3, tributary to rio Juruena at km 363 of road MT-170, Juína, 11°31’35.0”S 58°24’29.3”W. MZUSP 61115, 5, rio Criquiri, tributary to rio dos Patos, Nova Mutum, approx. 13°51’S 56°11’W.