Cheirodontinae (Malabarba, 1998)

Malabarba, Luiz R. & Jerep, Fernando C., 2014, Review of the species of the genus Serrapinnus Malabarba, 1998 (Teleostei: Characidae: Cheirodontinae) from the rio Tocantins-Araguaia basin, with description of three new species, Zootaxa 3847 (1), pp. 57-79 : 75-76

Key to the species of the Cheirodontinae occurring in the Atlantic drainages of northeastern Brazil, from the rio Tocantins-Araguaia to the rio Paraguaçú drainages

1. Lower lobe of caudal fin of males covered with cone shaped or papilla-like organs (see Malabarba et al., 2004: figs. 1 to 4). A conspicuous small black spot present at midlength of first branched anal-fin ray of males (see Malabarba et al., 2004: figs. 5–6 and 8). A dark brown nearly isosceles triangular shaped mark present in the area covering pelvic bone in males (see Malabarba et al., 2004: fig. 9)....................................................................2 ( Kolpotocheirodon )

1´. Lower lobe of caudal fin of males not covered with cone shaped or papilla-like organs. Conspicuous black spots lacking on branched anal-fin rays. Triangular mark in area covering pelvic bone absent....................................... 3

2. Dorsal fin lacking conspicuous black spots. 3–5 very small, vertical bars crossing lateral body stripe between pseudotympanum and area ventral to dorsal fin (see Malabarba et al., 2004: fig. 8). Twelfth to the 14 th or 15 th principal caudal-fin rays of males bearing hooks................................................................................................... Kolpotocheirodon theloura (headwaters of São Francisco and Paraná river basins near Brasília, DF, Brazil)

2´. Conspicuous small black spot present on soft tissue between midlength of first and second, and second and third dorsal-fin branched rays (see Malabarba et al., 2004: figs. 5 and 6). Vertical bars crossing lateral body stripe and hooks on caudal fin absent................................................. Kolpotocheirodon figueiredoi (Paraguaçu River drainage)

3. Base of lower caudal-fin lobe with hypertrophied group of scales forming small pouch................................ Compsura heterura (São Francisco River basin and northeastern coastal drainages; absent in Tocantins-Araguaia River basin)

3´. Base of lower caudal-fin lobe without hypertrophied scales................................................... 4

4. Ventral procurrent caudal-fin rays not hypertrophied or exposed along ventral margin of caudal peduncle of mature males. Thirteenth to 14 th caudal-fin rays bearing hooks associated with hypertrophied skin flaps in mature males ( Malabarba & Weitzman, 1999: figs. 3–6).................... Acinocheirodon melanogramma (São Francisco and Jequitinhonha river basins)

4´. Ventral procurrent caudal-fin rays hypertrophied and exposed ventrally in mature males. Caudal-fin rays without hooks or hypertrophied skin flaps in mature males.................................................................. 5

5. First through fourth or fifth branched anal-fin rays of mature males slab-shaped ( Malabarba & Jerep, 2012: fig. 3). Distal tip of ventral procurrent caudal-fin rays conical in mature males ( Malabarba & Jerep, 2012: fig. 3). Anal-fin rays iv–v, 14–17. Lateral line completely pored with 32–36 scales................... Ctenocheirodon pristis (Tocantins-Araguaia River basin)

5´. First through sixth or eighth branched anal-fin rays of mature males slab-shaped ( Fig. 4 ). Distal tip of ventral procurrent caudal-fin rays spatulate or scimitar-shaped in mature males ( Fig. 2 ). Anal-fin rays iii–iv,16–21.............. 6 ( Serrapinnus )

6. Three central cusps of dentary teeth expanded relative to other cusps and form a sharp-cutting edge. Lateral line completely pored.................... Serrapinnus heterodon (São Francisco River basin and northeastern Atlantic coastal drainages)

6´. Three central cusps of dentary teeth similar in shape to remaining cusps ( Figs. 3 , 7 , 9 , 11 ). Lateral line incomplete, with 5–10 pored scales (variable in S. tocantinensis , ranging from 6–36 scales)............................................. 7

7. Longitudinal black stripe wide and conspicuous, one or one and half scale deep, extending from posterior margin of opercle to caudal spot ( Fig. 8 ).................................................. S. sterbai (Tocantins-Araguaia River basin)

7´. Longitudinal black stripe narrow, extending from region below dorsal-fin base to caudal spot......................... 8

8. Longest unbranched dorsal- and pelvic-fin rays of males prolonged as filament ( Fig. 10 )........................................................................................... S. tocantinensis (Tocantins-Araguaia River basin).

8´. Longest unbranched dorsal- and pelvic-fin rays of males not prolonged as filament.................................. 9

9. Ventral procurrent caudal-fin rays 17–19................................ S. lucindai (Tocantins-Araguaia River basin)

9´. Ventral procurrent caudal-fin 16 or fewer.................................................................. 10

10. Ventral procurrent caudal-fin rays of mature males spatulate, forming keel along posterior ventral margin of caudal peduncle...................................... S. piaba (São Francisco River basin and northeastern coastal Atlantic drainages)

10´. Ventral procurrent caudal-fin rays of mature males scimitar-shaped and forming semicircle, with portion of ventral procurrent caudal-fin rays having resultant star-shape form with multiple points ( Fig. 2a ).................................... 11

11. Premaxillary teeth with 7 to 9 cusps ( Fig. 3a )............................... S. aster (Tocantins-Araguaia River basin).

11´. Premaxillary teeth with 5 cusps (see Jerep & Malabarba, 2014: fig. 3).......................................................................................... S. potiguar ( Ceará-Mirim River basin in Rio Grande do Norte state) .

Figures

FIGURE 2. Ventral procurrent caudal-fin rays of species of Serrapinnus from the rio Tocantins-Araguaia basin. (a) Serrapinnus aster, male, UFRGS 12023, 26.9 mm SL; (b) S. aster, female, UFRGS 12023, 35.7 mm SL; (c) S. lucindai, male, UFRJ 1260, 24.9 mm SL; (d) S. lucindai, female, UFRJ 1260, 25.9 mm SL; (e) S. sterbai, male, UFRGS 16447, 28.7 mm SL; (f) S. sterbai, female, UFRGS 16447, 29.6 mm SL; (g) S. tocantinensis, male, MCP 40417, 31.6 mm SL; (h) S. tocantinensis, female, MCP 40417, 33.4 mm SL. Lateral view, anterior to left. Scale bar = 1 mm.

FIGURE 3. Serrapinnus aster, MZUSP 115012, 25.2 mm SL; Scanning Electron Microscopy images showing (a) left side premaxilla; (b) maxilla; (c) dentary, and (d) detail of dentary teeth.

FIGURE 4. Anal fin of mature males of the species of Serrapinnus from rio Tocantins-Araguaia basin showing hypertrophied anal-fin rays and hooks shape and distribution. (a) Serrapinnus aster, male, UFRGS 12023, 26.9 mm SL; (b) S. lucindai, male, UFRJ 1260, 24.9 mm SL; (c) S. sterbai, male, UFRGS 16447, 29.7 mm SL; (d) S. tocantinensis, male, MCP 40417, 31.6 mm SL. Lateral view, anterior to left. Arrow head pointing to ligaments connecting approximately midlength of posterior face of proximal segment of lepidotrichia to proximal anterior face of lepidotrichia of the subsequent ray. Scale bar = 1 mm.

FIGURE 7. Serrapinnus lucindai, UFRJ 1260, 25.1 mm SL; Scanning Electron Microscopy images showing (a) left side premaxilla; (b) maxilla; (c) dentary, and (d) detail of the dentary teeth.

FIGURE 8. Serrapinnus sterbai (a) male, MZUSP 40359, 22.8 mm SL, Município de Arraias, periodic lake in the confluence of rio Paraná and rio Bezerra, Tocantins drainage, Tocantins State, Brazil; (b) male, MZUSP uncat., not measured, and (c) female, MZUSP uncat., not measured.

FIGURE 9. Serrapinnus sterbai, UFRGS 16447, 28.7 mm SL; Scanning Electron Microscopy images showing (a) left side premaxilla; (b) maxilla; (c) dentary, and (d) detail of dentary teeth.

FIGURE 10. Serrapinnus tocantinensis, (a) holotype, male, UFRGS 16442, 32.5 mm SL, córrego Fundo, tributary of rio das Garças, Município de Barra do Garças, Mato Grosso, Brazil; (b) paratype, female, UFRGS 12021, 29.9 mm SL, same data as holotype.

FIGURE 11. Serrapinnus tocantinensis, INPA 20986, 36.2 mm SL; Scanning Electron Microscopy images showing (a) right side premaxilla; (b) maxilla; (c) dentary, and (d) detail of dentary teeth.