Rhinopetitia melanohumeralis, Menezes & Netto-Ferreira, 2019

Menezes, Naércio A. & Netto-Ferreira, Andre L., 2019, A systematic review of Rhinopetitia Géry (Teleostei, Characiformes, Characidae) with descriptions of four new species and redescription of R. myersi Géry, Zootaxa 4700 (1), pp. 59-86 : 80-84

Rhinopetitia melanohumeralis , new species

Figures 22–25 , Table 5

Knodus hereresthes (not Eigenmann, 1908) – Thomaz et al., 2015 [in part, MNRJ 34678; multilocus phylogeny of the Stevardiinae ]

Holotype. MZUSP 124122 , female 40.0 mm SL, Mato Grosso, Campinápolis, Rio Culuene, Rio Xingu basin, 13°32’15’’S, 52°47’45”W, F.C.T. Lima, F.A. Machado, A.C. Ribeiro, C.L.R. Moreira, 02 October 2007

Paratypes. All from Brazil . MZUSP 98202 , 40 (22.0–40.0 mm SL, 5 C&S, 34.5–38.0 mm SL) collected with the holotype . MZUSP 98400 , 8 (25.0–40.0 mm SL), Mato Grosso, Paranaíta, left bank of Rio Teles Pires, Rio Tapajós basin, 09°27’06”S, 56°30’50”W, M.V. Loeb & A. de Castro, 20 January 2008 . INPA 59020 , 5 (40.0–44.0 mm SL) , MNRJ 51536 , (42.0–47.0 mm SL) , MPEG 38604 , 5 (38.5–46.0 mm SL) , MZUSP 96624 , 45 (25.0–47.0 mm SL) , UFRGS 27593 , 5 (40.0–43.0 mm SL), Mato Grosso, Peixoto de Azevedo, Rio Peixoto de Azevedo, tributary of Rio Teles Pires , Rio Tapajós basin, 10°13’14”S, 54°58’02”W, J. Birindelli, L. Sousa, A. L. Netto-Ferreira, M. Sabaj & N. Lujan, 16 October , 2007; MZUSP 89719 , 49 (23.0–37.5 mm SL), Mato Grosso, Paranatinga, Rio Culuene, Rio Xingu basin, 13°49’00”S, 53°15’00”W, A. Akama & J. Birindelli, 21 August 2006 . MZUSP 93242 , 18 (16.0–31.0 mm), Pará, Pimental, right bank of Rio Tapajós , 04°34’15”S, 56°15’39”W, L.M. Sousa & J.L. Birindelli, 11 November 2006 . MZUSP 74645 , 6 (28.0–35.0 mm SL), Mato Grosso, Alta Floresta, Rio Teles Pires Pesqueiro do Dentinho , 13°08’00”S, 59°50’00”W, F.A. Machado et al. July 1997 . MZUSP 96192 , 18 (19.0–28.0 mm SL) Mato Grosso ;. MZUSP 100038 , 4 (SL 29.0–32.5 mm), Mato Grosso, Paranaíta, Rio Teles Pires above Sete Quedas , 09°23’53”S, 56°34’37”W, Rio Tapajós basin, L.M. Sousa & A. L. Netto-Ferreira, 16 June 2008 . MZUSP 94123 , 36 (22.0–36.0 mm SL), Mato Grosso, Gaúcha do Norte, rio Culuene , 13°30’53”S, 53°05’40”W, F.C.T. Lima, F.A. Machado, C.A. Figueiredo, & J.L. Birindelli, May 2007 . MZUSP 91395 , 23 (20.0–32.0 mm SL), Mato Grosso, Gaúcha do Norte, Rio Curisevo, beach under bridge on road to Sorriso , about 30 km from Gaúcha do Norte , tributary of Rio Xingu , 13°12’58”S, 53°29’53”W, C. Moreira, I. Landim, A. Datovo & Oliveira, 19 October , 2004. MZUSP 124123 , 18 (26.0–34.0 mm), Pará, Jacareacanga, São Martins village, Rio Tapajós , 06°08’20”S, 57°40’02”W, F.C. Dagosta & H. Varella, 03 April 2013 . MZUSP 91396 , 3 (28.0–34.0 mm SL), Mato Grosso, Canarana, Rio Sete de Setembro, tributary of Rio Xingu , about 30 km west of Canarana , road MT 020 , 13°30’19”S, 52°25.5’57”W, C. Moreira, I. Landim, C. Nolasco & A. Datovo, 17 October 2004 . MZUSP 99939 , 3 (32.0–42.0 mm SL) and 99985 1, (35.0 mm SL), Pará, Jacareacanga, Rio Teles Pires below Sete Quedas , Rio Tapajós drainage, 09°20’38”S, 56°46’42”W, L.M. Sousa, & A.L. Netto-Ferreira, 10 June 2008 .

Diagnosis. Body depth in Rhinopetitia melanohumeralis , R. paucirastra and R. myersi (25.0–31.0% of SL, Fig. 4 , Tables 2 , 3, and 6) is deeper than in R. oligolepis , (19.1–24.0 % of SL, table 3), and R. nigrofasciata (20.0–24.8 % of SL, Table 4 ).The new species differs from R. oligolepis by having 5 versus 4 longitudinal scale rows from dorsal-fin origin to lateral line and 33–34 versus 34–35 vertebrae; from R. nigrofasciata by having 33–34 vs 35–36 vertebrae; and from R. paucirastra by having 13–17 vs 8–12 gill rakers on the external row on first gill arch and 35–38 vs 33–35 lateral line scales. Finally, R. melanohumeralis differs from R. myersi in having 35–38 vs 32–34 lateral line scales and 13–14 vs 12 longitudinal scale rows around caudal peduncle, and from R. potamorhachia by the lower number of teeth cusps on both jaws (4–5 vs. 7–9).

Description. Morphometrics of holotype and paratypes in Table 5 . Body small (largest examined specimen 47.0 mm SL). Head and body elongate and laterally compressed; greatest body depth at dorsal-fin origin. Profile distinctly convex from upper jaw to posterior nostril, slightly convex from latter point to dorsal-fin origin, straight along dorsalfin base, nearly straight to slightly concave from latter point to adipose-fin origin, and concave from latter point to anteriormost dorsal procurrent ray. Ventral body profile convex from tip of lower jaw to isthmus, nearly straight from that point to vertical through pectoral-fin origin, convex from latter point to pelvic-fin origin, and straight from that point to anal-fin origin. Ventral profile along anal-fin base straight and concave on caudal peduncle.

Mouth sub-terminal to nearly inferior; lower jaw short, included in upper jaw when mouth closed. Posterior tip of maxilla reaching slightly beyond vertical through anterior border of pupil. Outer premaxillary tooth row with 4 (31), 5 (163), 6 (60*), or 7 (2) teeth, each with four to five cuspidate teeth (5), inner row with 4 (256) five (5) cuspidate teeth ( Fig. 23 ). Maxillary ( Fig. 23 ) with 1 (1), 2 (93*), 3 (139), or 4 (23) teeth, all teeth about equally developed with five (3) to six cusps (2). Dentary ( Fig. 23 ) with 4 (256) anterior large teeth with five cuspidate teeth (5) followed by 2 (3), 3 (60), 4 (129*), 5 (46), 6 (10), or 7 (1) smaller three (3) to five (2) cuspidate teeth, gradually decreasing in size posteriorly. First gill arch with external and internal rows of gill rakers; external row with 13 (25), 14 (69*), 15 (100), 16 (54), or 17 (8) gill rakers. Branchiostegal rays 4 (5); 3 originating on anterior and 1 on posterior ceratohyal.

Scales cycloid. Lateral line complete; perforated scales 35 (75), 36 (131*), 37 (44), or 38 (1). Predorsal scales 11 (62), 12 (177*), or 13 (15). Scale rows between lateral line and dorsal-fin origin 5 (256); rows between lateral line and pelvic-fin origin 3 (15), or 4 (241*); circumpeduncular scales 13 (97*), or 14 (149). Single series of scales with sinuous posterior borders forming sheath along base extending to about 13 th anal-fin ray.

Pectoral-fin rays i, 10 (7), i, 11 (124*), i, 12, (114), or i,13 (11). Distal tip of longest pectoral-fin ray not reaching pelvicfin origin. Pelvic-fin rays i,6,i (225*) or i,7,i (19); tip of fin extending to anal-fin origin. Supraneurals 4 (1), 5 (2) or 6 (2), rod-shaped, or with discrete enlargement of dorsal portion; last supraneural located anterior to neural spines of 8 th (2) or 9 th (3) vertebral centra. Dorsal-fin rays ii,7, i (256). First dorsal-fin pterygiophore inserting behind neural spine of 10 th (1) or 11 th (4) centrum. Distal margin of extended dorsal fin straight to slightly convex. Dorsal-fin origin closer to caudal-fin base than to snout tip. Base of last dorsal-fin ray situated slightly anterior to vertical through anal-fin origin. Anal-fin rays iv–v, 15 (12), 16 (82*), 17 (105), 18 (55), or 19 (1), posterior most ray adnate. Anal fin with short, inconspicuous, anterior lobe including last unbranched ray plus first 5–6 branched rays. Distal margin of anal fin concave.

First anal-fin pterygiophore inserting behind haemal arch of centra 16 th (2), or 17 th (3). Adipose fin present. Principal caudal-fin rays 10/9 (256). Dorsal and ventral procurrent rays 10 (4), 11 (1) and 10 (5) respectively. Vertebrae 33 (2), or 34 (3).

Color in alcohol. Ground color pale to yellowish brown. Small dark chromatophores densely distributed on snout extending up on head until tip of supraoccipital spine leaving a light area on the anterior part of fontanel. Larger dark chromatophores on fourth and fifth infraorbital bones and upper median portions of opercle. Small dark chromatophores scattered over upper part of body above lateral line and above anal-fin base until below lateral line, fewer on anterior lower part of body.

Dark inconspicuous mid-lateral body stripe in freshly preserved specimens sometimes obscured by guanine extending from about vertical through dorsal-fin origin to caudal-fin base, enlarged over caudal peduncle. Very conspicuous dark humeral blotch slightly elongate vertically occupying three longitudinal scale rows. Mid-dorsal and adjacent scale rows densely pigmented with small dark chromatophores distributed over distal part of scales, but leaving light areas on basal and marginal portions of each scale. Larger dark chromatophores on central part of anterior half of midline predorsal scales.

All fins hyaline with few scattered dark chromatophores on dorsal, caudal, and anal fins and very few on pectorals, and pelvic fins.

Sexual dimorphism. Anal fin of sexually mature males ( Fig. 24 ) with bilateral hooks on largest unbranched ray and first four branched rays. Pelvic-fin ( Fig. 25 ) with hooks distributed on the six anteriormost branched rays.

Etymology. The specific name melanohumeralis is from the Latin words “melano” meaning black, dark and “humerus” meaning shoulder, is in reference to the conspicuous dark blotch on the humeral region on the sides of the body of this species.

Distribution. This species is so far known from small streams tributaries of the rivers Teles Pires, and Tapajós in the states of Mato Grosso and Pará, and Culuene, Curisevo and Sete de Setembro, flowing into the Xingu river basin, in the states of Mato Grosso and Pará, Brazil ( Fig. 9 )

Figures

FIGURE 4. Body depth as a function of standard length for the species of Rhinopetitia.

FIGURE 9. Map of northern South America showing collecting sites and type localities (star symbols) of the species of Rhinopetitia. Red, R. myersi; white, R. paucirastra; light blue, R. oligolepis; yellow, R. nigrofasciata; green, R. melanohumeralis. Some symbols may represent more than one locality.

FIGURE 22. Rhinopetitia melanohumeralis, new species, MZUSP 124122, holotype, female, 40.0 mm SL, Brazil, Mato Grosso, Paranatinga, Rio Culuene, Rio Xingu basin.

FIGURE 23. Rhinopetitia melanohumeralis, MZUSP 98202, 37.0 mm SL C&S, jaws and dentition, lateral view, lateral side, anterior at left.

FIGURE 24. Rhinopetitia melanohumeralis, MZUSP 98202, 37.0 mm SL C&S, sexually mature male; anal-fin rays, lateral view, left side, showing anal-fin hooks.

FIGURE 25. Rhinopetitia melanohumeralis, MZUSP 98202, 37.0 mm SL C&S, sexually mature male; pelvic-fin rays, ventral view, left side, showing pelvic-fin hooks.