Melanorivulus flavipinnis, Costa, Wilson J. E. M., 2017

Costa, Wilson J. E. M., 2017, Three new species of the killifish genus Melanorivulus from the central Brazilian Cerrado savanna (Cyprinodontiformes, Aplocheilidae), ZooKeys 645, pp. 51-70 : 55-59

Melanorivulus flavipinnis sp. n. Figs 4, 5, Table 2

Holotype.

UFRJ 6881, male, 28.5 mm SL; Brazil: Mato Grosso state: Rondonópolis municipality: stream tributary of Rio Anhumas, Rio São Lourenço drainage, Rio Paraguai basin, 16°48'16"S, 54°40'52"W, altitude approximately 420 m asl, road BR-070; W. J. E. M. Costa et al., 13 August 2016.

Paratypes.

UFRJ 6882, 2 males, 25.0-26.6 mm SL, 5 females, 22.3-39.4 mm SL; UFRJ 6883, 2 males, 22.5-25.6 mm SL, 2 females, 24.2-26.4 mm SL (C&S); CICCAA00279, 1 male, 25.7 mm SL, 1 female, 25.3 mm SL; collected with holotype.

Diagnosis.

Melanorivulus flavipinnis differs from all other species of the Melanorivulus dapazi group by the presence, in males, of seven or eight narrow red bars on the caudal fin, irregularly shaped and sometimes interconnected (vs. five or six dark red-brown regularly shaped and never interconnected bars in Melanorivulus regularis ; four or fewer short rudimentary bars, sometimes absent, in Melanorivulus dapazi ; bars always absent in Melanorivulus ignescens ) and by the caudal fin, in females, being yellow on the middle portion and reddish orange on marginal region (vs. yellow to pale pink on the whole fin in the remaining species). Also distinguished from all other congeners of the Melanorivulus dapazi group by the following combination of character states: 5-6 pelvic-fin rays (vs. 7 in Melanorivulus dapazi and Melanorivulus regularis ); 30-32 scales in longitudinal series (vs. 35-37 in Melanorivulus regularis ); female caudal spot inconspicuous in live fish (vs. conspicuous in Melanorivulus dapazi and Melanorivulus regularis ); caudal fin, in males, without distinctive orange margin (vs. with broad bright orange band along the whole margin in Melanorivulus dapazi ); anal fin, in males, yellow (vs. reddish orange in Melanorivulus ignescens ); in females, ventral surface of head with dark grey spots, often forming short stripe on chin (vs. without dark grey spots in Melanorivulus dapazi ); caudal-fin long, its length 34.1-38.7% SL (vs. short, length 26.8-33.1% SL in Melanorivulus ignescens ). Also distinguished from all other species of the Melanorivulus dapazi by the fourth ceratobranchial teeth arranged in two separate sections along the bone surface (vs. continuously arranged).

Description.

Morphometric data appear in Table 2. Body slender, sub-cylindrical anteriorly, slightly deeper than wide, compressed posteriorly. Greatest body depth at vertical just in front of pelvic-fin base. Dorsal and ventral profiles of trunk almost straight to slightly convex in lateral view; dorsal and ventral profiles of caudal peduncle nearly straight. Head moderately wide, sub-triangular in lateral view, dorsal profile nearly straight, ventral profile convex. Jaws short, snout weakly pointed in lateral view. Jaw teeth numerous, conical, irregularly arranged, outer teeth larger and slightly curved, inner teeth straight.

Dorsal and anal fins short, tip slightly pointed in males, rounded in females. Caudal fin oval, longer than deep. Pectoral fin rounded, posterior margin reaching vertical at approximately 80-90% of length between pectoral-fin and pelvic-fin bases. Pelvic fin small, tip reaching between base of first and third anal-fin rays in males, reaching urogenital papilla in females; pelvic-fin bases medially in close proximity. Dorsal-fin origin on vertical through base of 8th anal-fin ray. Dorsal-fin rays 9-10; anal-fin rays 14-15; caudal-fin rays 30-31; pectoral-fin rays 13; pelvic-fin rays 5-6. No contact organs on fins.

Scales small, cycloid. Body and head entirely scaled, except anterior ventral surface of head. Body squamation extending over anterior 25% of caudal-fin base; no scales on dorsal and anal-fin bases. Frontal squamation F-patterned, rarely E-scale anteriorly overlapping F-scale; E-scales not overlapping medially; scales arranged in regular circular pattern around A-scale without exposed margins. Longitudinal series of scales 30-32; transverse series of scales 8; scale rows around caudal peduncle 16. No contact organs on scales. Cephalic neuromasts: supraorbital 3 + 3, parietal 1, anterior rostral 1, posterior rostral 1, infraorbital 1 + 10-11 + 1, preorbital 2, otic 1, post-otic 1, supratemporal 1, median opercular 1, ventral opercular 1, pre-opercular 2 + 4, mandibular 2-3 + 1, lateral mandibular 1, paramandibular 1.

Jaw teeth numerous, conical, irregularly arranged, outer teeth larger and slightly curved, inner teeth straight. Ventral process angulo-articular short, pointed. Ventral process of palatine short, slightly contacting quadrate. Mesopterygoid slender, posterior tip not reaching metapterygoid. Metapterygoid sub-rectangular, with constriction on middle portion. Dorsal portion of preopercle short and pointed, channel rudimentary. Basihyal sub-triangular, greatest width about 50% of length; basihyal cartilage about 15-25% of total basihyal length. Six branchiostegal rays. Second pharyngobranchial teeth absent. Interarcual cartilage rudimentary. Fourth ceratobranchial teeth present, continuously arranged. Gill-rakers on first branchial arch 1 + 8. Vomerine teeth 2. Dermosphenotic present. Ventral process of posttemporal absent. Second proximal radial of dorsal fin between neural spines of 19th and 21st vertebrae, first proximal radial of anal fin between pleural ribs of 13th and 15th vertebrae. Total vertebrae 30-31.

Colouration.

Males. Flank metallic green-blue to metallic light blue, sometimes purple-blue above anal fin; oblique narrow orangish red bars irregularly arranged, often forming chevron-like marks anteriorly directed; short light red stripe on humeral region; horizontal rows of reddish orange dots on antero-ventral part of flank, between bases of pectoral and pelvic fins; pale dark grey blotches on postorbital region mainly visible when fish is exposed to strong light. Dorsum light yellowish-brown with black dots, venter white. Dorsal portion of head side light brown, ventral portion white; pale golden iridescence on opercular region. Jaws dark grey. Iris pale yellow, sometimes with dark brown bar on anterior and posterior portions. Dorsal fin light yellow with seven or eight narrow oblique red bars, often forming reticulate pattern on distal portion of fin. Anal fin pale blue on its proximal half, with faint oblique red bars, light yellow in its distal half, distal region becoming gradually dark reddish brown on marginal border, distal margin with high concentration of melanophores. Caudal fin bright yellow, more intensely pigmented on dorsal and ventral portions, with seven or eight narrow red bars, irregularly shaped and sometimes interconnected. Pectoral fin yellowish hyaline. Pelvic fin light blue with orangish brown anterior margin.

Females. Side of trunk and head similar to males, but with paler colours. Ventral surface of head white, with dark grey spots often forming short stripe on chin. Dorsal fin pale yellow, with oblique grey bars; broad dark grey to black band on distal margin. Anal fin green-yellow, basal portion light blue with small red spots. Caudal fin pale yellow on middle portion, reddish orange on marginal region, with five to seven dark grey bars, often interconnected; small black spot, smaller than pupil, on dorso-basal portion of fin overlapping anterior-most bar, conspicuous only in preserved specimens; broad dark grey to black band on whole fin margin.

Distribution.

Known only from the type locality, a small stream tributary to the Rio Anhumas, Rio São Lourenço drainage, Rio Paraguai basin, central Brazil, altitude approximately 420 m asl (Fig. 3).

Etymology.

From the Latin, flavipinnis (yellow fins), referring to the bright yellow colouration of the caudal fin in males.