A new Hyphessobrycon (Ostariophysi: Characiformes: Characidae) from the middle Amazon basin, Brazil Author Lima, Flávio C. T. Author Coutinho, Daniel P. Author Wosiacki, Wolmar B. text Zootaxa 2014 3872 2 167 179 journal article 10.11646/zootaxa.3872.2.3 f8b084ec-ebaa-47a8-a34a-bcd2547aa521 1175-5326 226263 7886E4B9-C2A3-45A6-83D1-3D2C969325CB Hyphessobrycon montagi , new species Figures 1–2 Holotype . MPEG 29970, 1, 31.1 mm SL , Brazil , Pará, Juruti, Igarapé Socó Barroso (trib. rio Arapiuns), 2°27’54”S , 56°0’25”W , L.F.A. Montag, 3 April 2006 . Paratypes . All from Brazil , Pará, Juruti. MPEG 10340, 36, 17.7–27.9 mm SL , same data as holotype . Following lots from Igarapé Socó Barroso (trib. rio Arapiuns), 2°27’54”S , 56°0’25”W : MPEG 14730, 24, 11.3–22.4 mm SL , W.B. Wosiacki, 21 Feb 2008 ; MPEG 14735, 193, 11.4–25.9 mm SL , W.B. Wosiacki, 1 Dec 2007 ; MPEG 24852, 7, 20.5–25.7 mm SL , W.B. Wosiacki, 21 Feb 2008 ; MPEG 13860, 21, 18.1–25.9 mm SL , W.B. Wosiacki, 16 May 2007 ; MPEG 26055, 48, 10.8–27.7 mm SL ; MPEG 26053, 108, 10.4–25.7 mm SL , M. Mendonça, 5 Dec 2012 . Following lots from Igarapé Mutum (trib. rio Aruã , trib. rio Branco, trib. rio Arapiuns), 2°36’44.8”S , 56°11’37.3”W : MPEG 10449, 80, 13.1–26.5 mm SL , W.B. Wosiacki, 8 Sept 2002 ; MPEG 10344, 43, 17.2–30.8 mm SL ; ZUEC 8319, 20, 20.6–28.8 mm SL , W.B. Wosiacki & A. Bezerra, 6 Aug 2004 ; MPEG 24846, 11, 15.8–27.0 mm SL , W.B. Wosiacki, 19 Feb 2008 ; MPEG 24865, 28, 17.6–26.6 mm SL ; MPEG 24841, 12, 9.0– 25.7 mm SL : R. Raiol, 19–20 Nov 2010 ; MPEG 14734, 333, 9.5–28.0 mm SL , A. Hercos, 27 Nov 2007 ; MPEG 10336, 15, 18.6–30.4 mm SL ; ZUEC 8318, 10, 21.4–27.9 mm SL , L.F.A. Montag, 3 March 2006 ; MPEG 10458, 4, 12.4–25.5 mm SL , W.B. Wosiacki & A.S. Bezerra, 2 Aug 2004 ; MPEG 24858, 89, 14.6–27.4 mm SL , W.B. Wosiacki, 3 Jun 2010 ; MPEG 24830, 17, 8.5–22.4 mm SL , R. Raiol, 4 Dec 2008 ; MPEG 14740, 354, 12.3–28.2 mm SL ; ANSP 197188, 10, 18.0– 21.6 mm SL ; INPA 45068, 20, 19.8–28.5 mm SL ; MCP 48264, 10, 16.7–26.0 mm SL , A. Hercos, 27 Nov 2007 ; MPEG 24824, 147, 16.2–29.4 mm SL , W.B. Wosiacki, 19 Feb 2008 ; MPEG 30361, 13, 13.3–27.1 mm SL , M.B. Mendonça, L.A.W. Peixoto & F.L Felier, 0 6 Dec 2013 . Following lots from Igarapé Rio Branco, trib. rio Arapiuns, 2°28’13.9”S , 56°0’12.3”W : MPEG 10464, 8, 16.2–24.0 mm SL , W.B. Wosiacki & A.S. Bezerra, 8 Aug 2004 ; MPEG 10342, 10, 19.7–29.4 mm SL , W.B. Wosiacki, 8 Aug 2004 . Following lots from Igarapé Rio Branco, trib. rio Arapiuns, 2°20’57.9”S , 56°1’22.5”W : MPEG 10470, 26, 15.8–25.5 mm SL , W.B. Wosiacki & A.S. Bezerra, 9 Aug 2004 ; MPEG 26056, 54, 17.7–25.0 mm SL , M. Mendonça, 27 Nov 2012 ; MPEG 24869, 83, 10.6–26.3 mm SL , W.B. Wosiacki, 27 Nov 2010 ; MPEG 24863, 4, 19.6–23.8 mm SL , R. Raiol, 6 June 2010 ; MPEG 24840, 24, 10.7–27.2 mm SL , R. Raiol, 18 Sept 2009 . Following lots from Igarapé São Francisco (trib. rio Arapiuns), 2°34’51.5”S , 55°54’14.5”W : MPEG 7914, 92, 13.3–29.1 mm SL ; MZUSP 115389, 10, 21.3–26.5 mm SL , W.B. Wosiacki, 12 Aug 2004 ; MPEG 24857, 6, 18.2–26.6 mm SL , MPEG 24859, 6, 17.2–28.1 mm SL , R. Raiol, 4 June 2010 ; MPEG 24839, 31, 13.6–27.2 mm SL , R. Raiol, 24 Sept 2009 . Not types . All from Brazil , Pará, Juruti: Following lots from Igarapé Socó Barroso (trib. rio Arapiuns), 2°27’54”S , 56°0’25”W : MPEG 12884, 59, 10.3–26.4 mm SL ; MPEG 12873, 30, 10.3–18.1 mm SL ; MPEG 12890, 16, 17.9–26.8 mm SL ; MPEG 12877, 51, 10.2–26.2 mm SL ; MPEG 12876, 144, 9.2–26.4 mm SL , L.F.A. Montag, 12–13 Dec 2006 . MPEG 10455, 14, 14.0– 18.4 mm SL , L.F.A. Montag, 4 Mar 2006 ; MPEG 11050, 30, 11.3–22.2 mm SL ; MPEG 11041, 1, 13.3 mm SL ; MPEG 11052, 17, 15.1–24.4 mm SL ; MPEG 11049, 22, 15.0– 25.3 mm SL , A. Hercos, 18–19 Aug 2006 ; MPEG 12978, 15, 12.2–24.1 mm SL , L.F.A. Montag, 19 Aug 2006 ; MPEG 10338, 136, 17.1–25.5 mm SL ; 10, 20.1–27.9, CS, L.F.A. Montag, 4 Mar 2006 ; MPEG 24829, 1, 19.3 mm SL , W.B. Wosiacki, 20 Feb 2008 ; MPEG 24860, 16, 14.7–23.3 mm SL , R. Raiol, 0 5 Jun 2010 ; MPEG 24844, 34, 13.7–25.8 mm SL , R. Raiol, 23 Sep 2009 ; MPEG 24851, 5, 10.6–22.6 mm SL , W.B. Wosiacki, 21 Feb 2008 ; MPEG 24838, 119, 15.7–17.1 mm SL , R. Raiol, 11 Dec 2008 ; MPEG 24850, 6, 17.021. 5 mm SL , W.B. Wosiacki, 21 Feb 2008 ; MPEG 24861, 6, 15.0– 23.5 mm SL , R. Raiol, 5 June 2010 ; MPEG 24867, 18, 17.4–27.2 mm SL , R. Raiol, 21 Nov 2010 ; MPEG 24843, 40, 10.3–25.4 mm SL , R. Raiol, 23 Sep 2009 ; MPEG 13796, 12, 18.1–23.2 mm SL , W.B. Wosiacki, 16 May 2007 . Following lots from igarapé Mutum (trib. rio Aruã , trib. rio Branco, trib. rio Arapiuns), 2°36’44.8”S , 56°11’37.3”W : MPEG 10459, 23, 11.6–22.7 mm SL , W.B. Wosiacki, 9 Sept 2002 ; MPEG 10473, 1, 12.2 mm SL , W.B. Wosiacki, 6 Aug 2004 ; MPEG 14752, 29, 14.2–25.6 mm SL ; MPEG 24848, 9, 20.9–22.8 mm SL ; MPEG 24847, 9, 14.9–23.3 mm SL , W.B. Wosiacki, 19 Feb 2008 ; MPEG 12875, 150, 8.9–28.4 mm SL ; MPEG 12881, 60, 9.7–27.8 mm SL ; MPEG 13003, 12, 9.9–16.6 mm SL ; MPEG 13005, 25, 9.4–15.9 mm SL ; MPEG 12882, 1, 25.0 mm SL ; MPEG 12977, 16, 11.4–16.5 mm SL , L.F.A. Montag, 11–12 Dec 2006 ; MPEG 10461, 15, 20.1–24.5 mm SL ; MPEG 10460, 14, 19.5–25.1 mm SL ; MPEG 10453, 49, 18.6–32.1 mm SL , L.F.A. Montag, 3 March 2006 ; MPEG 11048, 3, 18.1–20.9 mm SL ; MPEG 11046, 3, 16.8–20.3 mm SL ; MPEG 11044, 44, 17.5–28.9 mm SL ; MPEG 11045, 13, 11.6–21.1 mm SL , A. Hercos, 17 Aug 2006 ; MPEG 11042, 5, 22.5–28.4 mm SL ; MPEG 11054, 1, 15.0 mm SL ; MPEG 10454, 8, 16.9–26.2 mm SL , A. Hercos, 3 March 2006 ; MPEG 14388, 13, 9.3–19.1 mm SL ; MPEG 14360, 1, 26.1 mm SL ; MPEG 14363, 2, 14.0– 15.7 mm SL , A. Hercos, 27 Nov 2007 ; MPEG 24855, 7, 16.3–26.5 mm SL , R. Raiol, 3 June 2010 ; MPEG 24864, 1, 19.3 mm SL ; MPEG 24866, 7, 17.8–22.8 mm SL , R. Raiol, 19 Nov 2010 ; MPEG 24831, 1, 16.1 mm SL , R. Raiol, 4 Dec 2008 ; MPEG 26054, 7, 13.6–24.6 mm SL , M. Mendonça, 28 Nov 2012 ; MPEG 24842, 19, 21.3–27.0 mm SL , R. Raiol, 20 Sep 2009 ; MPEG 24832, 88, 17.3–29.0 mm SL , R. Raiol, 0 4 Dec 2008 ; MPEG 26057, 31, 13.8–28.3 mm SL , M. Mendonça, 28 Nov 2012 ; Following lots from Igarapé Rio Branco, trib. rio Arapiuns, 2°20’57.9”S , 56°1’22.5”W : MPEG 10472, 21, 13.5–23.2 mm SL , W.B. Wosiacki & A.S. Bezerra, 11 Aug 2004 ; MPEG 10463, 6, 16.9–20.9 mm SL , W.B. Wosiacki & A. Bezerra, 14 Aug 2004 ; MPEG 10465, 2, 20.1–22.0 mm SL , W.B. Wosiacki, 12 Aug 2004 ; MPEG 10466, 7, 13.6–20.9 mm SL , W.B. Wosiacki & A.S. Bezerra, Aug 2004 ; MPEG 10469, 13, 11.1–19.2 mm SL , W.B. Wosiacki & A.S. Bezerra, 8 Aug 2004 ; MPEG 10456, 29, 14.1–20.0 mm SL , W.B. Wosiacki & A. Bezerra, 11 Aug 2004 ; MPEG 10462, 2, 14.2–19.2 mm SL , W.B. Wosiacki & A.S. Bezerra, 9 Aug 2004 ; MPEG 15090, 5, 18.3–23.0 mm SL , W.B. Wosiacki, 18 Feb 2008 ; MPEG 24833, 20, 13.3–23.7 mm SL , R. Raiol, 6 Dec 2008 ; MPEG 24834, 25, 18.0– 24.3 mm SL , R. Raiol, 6 Dec 2008 ; MPEG 24862, 4, 20.4–26.0 mm SL , R. Raiol, 6 Jun 2010 ; MPEG 24854, 1, 22.5 mm SL , R. Raiol, 18 Sep 2009 ; MPEG 24870, 48, 17.3–25.5mm SL , R. Raiol, 27 Nov 2010 ; MPEG 24823, 5, 21.8–24.6 mm SL , W.B. Wosiacki, 18 Feb 2008 ; MPEG 26508, 42, 16.2–21.0 mm SL , M. Mendonça, 27 Nov 2012 . Following lots from Igarapé Rio Branco, trib. rio Arapiuns, 2°28’13.9”S , 56°0’12.3”W : MPEG 10467, 1, 19.3 mm SL , W.B. Wosiacki & A.S. Bezerra, 8 Aug 2006 ; MPEG 10471, 7, 16.0– 24.1 mm SL , W.B. Wosiacki & A.S Bezerra, 8 Aug 2004 . Following lots from Igarapé São Francisco (trib. rio Arapiuns), 2°34’50.7”S , 55°54’14.5”W : MPEG 12880, 66, 12.2–21.7 mm SL , L.F.A. Montag, 15 Dec 2006 ; MPEG 11057, 97, 10.7–26.3 mm SL ; MPEG 11053, 133, 11.5–26.4 mm SL , A. Hercos, 19–20 Aug 2006 ; MPEG 12886, 78, 12.2–22.6 mm SL , W.B.Wosiacki, 14 Dec 2006 ; MPEG 13815, 5, 19.0– 26.7 mm SL , W.B. Wosiacki, 15 May 2007 ; MPEG 13751, 17, 20.0– 27.8 mm SL , W.B. Wosiacki, 15 May 2007 ; MPEG 24856, 4, 18.7–20.0 mm SL , R. Raiol, 4 June 2010 ; MPEG 24825, 9, 17.9–23.9 mm SL , W.B. Wosiacki, 20 Feb 2008 ; MPEG 24868, 75, 16.5–30.6 mm SL , R. Raiol, 21 Nov 2010 ; MPEG 24835, 60, 10.2–22.0 mm SL , R. Raiol, 10 Dec 2008 ; MPEG 24836, 32, 14.2–25.5 mm SL , R. Raiol, 10 Dec 2008 . Following lots from Igarapé São Francisco (trib. rio Arapiuns), 2°27’54.0”S , 56°0’25.2”W : MPEG 24827, 26, 13.0– 23.1 mm SL , W.B. Wosiacki, 21 Feb 2008 ; MPEG 24826, 8, 18.7–22.5 mm SL , W.B. Wosiacki, 20 Feb 2008 ; MPEG 24837, 25, 12.5–22.6 mm SL , R. Raiol, 11 Dec 2008 ; MPEG 14377, 74, 9.1–23.2 mm SL , A. Hercos, 1 Dec 2007 ; MPEG 14501, 1, 12.2 mm SL , Igarapé da Ponte, 2°10’49”S , 56°4’40”W ; A. Hercos, 30 Nov 2007 . Diagnosis. Hyphessobrycon montagi , new species , can be diagnosed from all its congeners, with exception of H. balbus Myers , H. bifasciatus Ellis , H. columbianus Zarske & Géry , H. condotensis Regan , H. flammeus Myers , H. griemi Hoedeman , H. isiri Almirón, Casciotta & Körber , H. itaparicensis Lima & Costa, H. savagei Bussing , H. sebastiani Garcia-Alzate, Román-Valencia & Taphorn , H. togoi Miquelarena & López , H. tortuguerae Böhlke , and H. weitzmanorum Lima & Moreira by the possession of two well-defined humeral blotches. It can be diagnosed from all these species by the presence of a well-defined caudal peduncle blotch (vs. caudal peduncle blotch absent in all aforementioned species, with the exception of H. isiri and H. togoi ), by an horizontally-elongated oval, very well-defined first humeral blotch (vs. first humeral blotch moderately conspicuous, vertically elongated, and approximately rectangular in shape), and by the fact that the first and second humeral blotches are connected via a narrow, short stripe (vs. humeral blotches not connected). Description. Morphometric data of holotype and selected paratypes presented in Table 1 . Body compressed, moderately high. Greatest body depth at dorsal fin origin. Dorsal profile of head convex from upper lip to vertical through middle of orbit; straight from latter point to tip of supraoccipital spine. Predorsal profile of body slightly convex, posteroventrally inclined along dorsal-fin base. Body profile straight to slightly convex from dorsal-fin base terminus to adipose fin; slightly concave between latter point to origin of anteriormost procurrent caudal-fin ray. Ventral profile of head and body convex from lower lip to anal-fin origin. Body profile along anal-fin base straight and posterodorsally inclined. Ventral profile of caudal peduncle slightly concave. TABLE 1. Morphometric data of Hyphessobrycon montagi , new species . N = Number of specimens measured.
N Holotype Range Mean
Standard length (mm) 82 31.1 21.6–31.1 -
Percents of standard length
Depth at dorsal-fin origin 82 36.7 28.3–37.7 32.0
Snout to dorsal-fin origin 82 50.8 47.7–52.6 49.9
Snout to pelvic-fin origin 82 47.9 42.1–49.7 46.6
Snout to anal-fin origin 82 63.7 57.3–64.8 60.8
Dorsal-fin length 76 29.9 24.8–33.6 29.5
Pectoral-fin length 80 22.2 18.6–26.6 22.9
Pelvic-fin length 76 17.7 15.0–22.8 18.7
Anal-fin base length 82 29.6 25.3–33.9 29.7
Caudal-peduncle depth 82 6.8 6.1–8.8 7.3
Caudal-peduncle length 81 11.6 10.3–16.3 13.8
Bony head length 82 27.7 26.1–29.8 27.9
Percents of head length
Horizontal eye diameter 82 43.0 38.2–50.0 43.8
Snout length 82 25.6 20.3–30.0 24.4
Least interorbital distance 82 31.4 26.1–34.2 30.9
Upper jaw length 82 54.7 43.1–55.7 49.2
FIGURE 1. A) Hyphessobrycon montagi , new species , holotype, MPEG 29970, 31.1 mm SL: Brazil, Pará, Juruti, Igarapé Socó Barroso. B) Hyphessobrycon montagi new species , paratype, ZUEC 8319, 28.8 mm SL; Brazil, Pará, Juruti, Igarapé Mutum. C) Hyphessobrycon montagi , new species , paratype, MPEG 10344, 29.4 mm SL: Brazil, Pará, Juruti, Igarapé Mutum. FIGURE 2. Hyphessobrycon montagi , new species , MPEG 30361, 27.1 mm SL, living specimen photographed immediately after collection; Brazil, Pará, Juruti, Igarapé Mutum. FIGURE 3. Hyphessobrycon montagi , new species , paratype, scanning electron micrographs (SEM) showing lateral view of left premaxillary (A), maxillary (B), and dentigerous portion of maxillary (B1), MPEG 24832, 28.6 mm SL; mesial view of left dentary (C), MPEG 24842, 27.2 mm SL. Jaws equal, mouth terminal. Posterior terminus of maxilla reaching vertical through middle of orbit. Premaxillary teeth in two rows ( Fig. 3 ). Outer row with 2*(31), 3(49), or 4(5) relatively compressed, tricuspidated, elongated teeth. Inner row with 5*(85) or 6(1) relatively compressed, tri- to pentacuspidated teeth. Maxilla with 2(1), 3(1), 4(4), or 5(4) uni- to tricuspidated teeth. Anteriormost teeth larger. Dentary with 13(4), 14(4), or 16(2) teeth, three anteriormost teeth larger, relatively bulky, pentacuspidated, fourth teeth smaller, tricuspidated. Remaining dentary teeth considerably smaller, cylindrical, all unicuspidated ( Figure 3 ). Scales cycloid, with 4 to 7 radii strongly marked, from focus to posterior border of scales; circuli weakly marked proximally, but absent distally (‘‘ Hemigrammus type’’ of Cockerell, 1914 ). Lateral line slightly decurved ventrally, incompletely pored, with 5(9), 6(28), 7(27), 8*(14), or 9(1) perforated scales. Lateral series scales including lateral line scales 27(2), 28(7), 29(17), 30*(19), 31(13), 32(7), 33(9), or 34(7). Horizontal scale rows between dorsal-fin origin and lateral line 5*(82). Horizontal scale rows between lateral line and pelvic-fin insertion 3*(82). Scales along middorsal line between distal tip of supraoccipital process and origin of dorsal fin 8–10. Horizontal scale rows around caudal peduncle 10*(28), 11(43), or 12(10). Single row of 3–5 scales covering base of anteriormost anal-fin rays. Caudal fin not scaled. Dorsal-fin rays ii, 9* (ii, 8 in a single specimen, out of 82), not including small ossification anterior to first unbranched ray, discernible only in CS specimens, present in eight out of nine CS individuals. Dorsal fin pointed, last unbranched and two anteriormost branched rays considerably more elongated than remaining rays, forming roughly a falcated tip. Dorsal-fin origin slightly anterior to middle of standard length. Base of posteriormost dorsalfin ray at vertical through anal-fin origin. First dorsal-fin pterygiophore inserting posterior to neural spine of 8(8) or 9(1) vertebrae. Adipose fin present. Anal-fin rays iii, 18(7), 19*(36), 20(29), 21(9), or 22(1). Anal fin with moderately developed anterior fin lobe, last unbranched and anteriormost 4–5 branched fin rays longer than remaining anal-fin rays. Anteriormost anal-fin pterygiophore inserting behind haemal spine of 13(1) or 14(8) vertebrae. Pectoral-fin rays i, 9(11), 10*(58), or 11(13). Pectoral fin pointed, its tip reaching vertical through pelvic-fin insertion. Pelvic-fin rays i,7(82). Pelvic fin pointed, its tip reaching vertical through anal-fin origin. Caudal fin forked, lobes slightly rounded, similar in size. Principal caudal-fin rays 10+9(6), 10+8(2). Dorsal procurrent caudal-fin rays 9(1), 10(4), or 11(4), and ventral procurrent caudal-fin rays 7(1), 8(5), or 9(3). First gill arch with 1(2), 2(6), or 3(1) hypobranchial, 8(7) or 9(2) ceratobranchial, 1(9) on cartilage between ceratobranchial and epibranchial, and 5(7) or 6(2) epibranchial gill-rakers. Vertebrae 31(9), 32(8), 33(1), or 34(1). Supraneurals 3(1), or 4(17). Branchiostegal rays four; three branchiostegal rays originating from anterior ceratohyal and one from posterior ceratohyal. Color in alcohol. Ground color tan, slightly darker dorsally. Silvery pigmentation in specimens retaining guanine present on opercular and infraorbital bones. Lower lip, snout, and top of head densely covered by small dark chromatophores, resulting in overall dark pigmentation. Opercle and infraorbital bones with large, numerous dark chromatophores. Gular area clear to tan. Mid-dorsal scale row with dense concentration of dark chromatophores, forming a discrete, blurred line. First to second and upper half of the third lateral scale rows anterior to, and first and upper half of second lateral scale row posterior to, dorsal-fin terminus, with dense concentration of dark chromatophores on scale margins, forming a distinctive reticulated pattern. Fourth lateral scale row clear, with few scattered, small dark chromatophores, forming a distinctive clear lateral band extending from immediately above humeral area to caudal peduncle. Some specimens retaining guanine with an elongated silvery blotch at the upper half of caudal peduncle. Two humeral spots, both very conspicuous and connected to each other via a short stripe. First humeral blotch large, roughly oval in shape, intensely dark-pigmented, situated at the lateral-line level, extending longitudinally from first to fourth or fifth lateral line scales and horizontally two scales rows high. Second humeral blotch smaller than first humeral blotch, roughly shovel-shaped, slightly less pigmented than first one, extending longitudinally from sixth to seventh or eighth lateral-line scales, situated in scale row immediately above lateral line. Specimens retaining guanine with silvery pigmentation surrounding first humeral blotch. Narrow midlateral dark stripe formed by chromatophores at myosepta between hypaxial and epaxial bundles of muscles from blotch terminus to anterior portion of caudal peduncle. Lateral surfaces of body below midlateral line and posterior to second humeral blotch with dense concentration of small dark chromatophores, forming an overall smoky pattern. Lower portion of abdominal region and anal-fin basis clear, with few dark chromatophores. Narrow, subjacent stripe of dark pigmentation located dorsal to anal-fin base, extending approximately along region where hypaxial musculature and muscles of anal fin meet, sub-parallel to anal-fin base. Caudal peduncle blotch large, rounded, situated on middle and lower portions of caudal peduncle and extending into middle caudal-fin rays. Caudal-fin lobes and remaining fins hyaline, with scattered, small dark chromatophores on interradial membranes, except for distal portion of anteriormost dorsal- and anal-fins, which possess a slightly more dense concentration of dark chromatophores. Color in life. Overall color pattern clear, light beige dorsally, plumbeous gray on anterior portion of lower half of body. Tip of snout and dentary light beige; upper half of eye dark red; a narrow longitudinal straight red line extending from area immediately above first humeral blotch to caudal peduncle, where red pigmentation extends across most of its upper half, above the dark caudal peduncle blotch. Yellowish pigmentation over pelvic fin, scattered across anterior portion of anal fin and dorsal fin ( Figure 2 ). Sexual dimorphism. None detected. Bony hooks on anal and pelvic fins of mature males, a common dimorphic feature among characids ( Malabarba & Weitzman, 2003 ) were not found in any specimens. Since a large sample of the species was examined (n = 4402), with specimens collected spanning most months of the year (February–June, August–December), it seems safe to assume that Hyphessobrycon montagi never develops fin hooks. See “Ecological notes”, from observations on the development of the urogenital papilla in males and females. Distribution. So far only known from the headwaters of the rio Arapiuns (rio Branco and rio Aruã ), lower rio Tapajós basin, and from a small direct tributary of the Rio Amazonas (igarapé da Ponte), Juruti municipality, Pará state, Brazil ( Figure 4 ). FIGURE 4. Map of middle Amazon, showing the distribution of Hyphessobrycon montagi , new species (type locality indicated by a red dot). Ecological notes. Hyphessobrycon montagi was exclusively collected at clear-water terra firme streams, i.e., streams dissecting the uplands, above the periodically flooded igapó forest, as the Igarapé Socó Barroso, the type locality ( Figure 5 ). Streams where Hyphessobrycon montagi specimens were collected range from 0.80 to 20 meters wide, with a maximum depth of 1.65 meters, and present moderate water current ( 0.1–0.7 m /s), with clear, sandy bottom with pebbles, mud, leaf litter, and submerged logs, often also presenting aquatic macrophytes. The pH ranged from 5.8 to 7.44, and the water temperature from 24.9 to 29.1°C. All collecting sites are within an unbroken, continuous primary/selectively logged forest area. Dissection revealed that females collected in March (MPEG 10336, 25.0– 30.4 mm SL) and August (MPEG 10344, 27.7 mm SL) presenting a relative large, pointed urogenital papilla, presented ripe oocytes. Mature males also display a pointed papilla, which seems to be, however, slightly smaller than the one presented by mature females (MPEG 10344, 25.4–27.6 mm SL). Etymology. The specific name, montagi , is in honor to our colleague and friend Luciano F.A. Montag (“Miúdo”), who collected part of the material of the species, and is in recognition of his contributions to the knowledge of the ichthyofauna from the lower portion of the Amazon basin. A genitive noun.