Rivulus rutilicaudus, Costa, 2005

Rivulus rutilicaudus View in CoL , new species

Figs. 8-9 View Fig View Fig

Rivulus pictus View in CoL ( non Costa, 1989). - Costa, 1995a: 216 (misidentification, specimens from Mineiros).

Holotype. UFRJ 5965 , male,22.9 mmSL; Brazil: EstadodeGoiás: Município de Serranópolis, rio Verde floodplains, rio Paraná basin , road BR-060, 18 o 22’31.5”S 52 o 0’59.5”W, altitude 531 m; by W. J. E. M. Costa, B. B. Costa and C. P. Bove, 15 January 2004.

Paratypes. Brazil: Estado de Goiás: rio Verde drainage, rio Paraná basin : UFRJ 5966 , 4 males, 15.8-20.9 mm SL, 4 females, 15.4-22.8 mm SL, 3 juveniles of undetermined sex, 11.5-15.1 mm SL ; MCP 36124 ; 1 male, 16.3 mm SL, 1 female, 15.4 mm SL ; UFRJ 5967 , 2 males, 17.5-17.6 mm SL, 1 female, 18.5 mm SL (c&s); collected with the holotype .

Additional material (non type specimens). UFRJ 2208 , 9 ex.; stream tributary to the upper rio Verde drainage , rio Paraná basin , road BR-364, 19 km SE from the city of Mineiros, Município de Mineiros; W. J. E. M. Costa, A. Sarraf, R. D’Arrigo and G. Carvalho, 16 Sep 1994 .

Diagnosis. Distinguished from its congeners in possessing a dark orangish red caudal fin in females ( vs. caudal fin hyaline or pale colored). Also distinguished from all other species of the R. punctatus group by the following combination of features: 10-12 dorsal fin rays ( vs. 8-10), 34-35 scales on the longitudinal series ( vs. 29-31), dorsal-fin origin at vertical between base of eighth and ninth anal-fin ray ( vs. between base of seventh and eighth or ninth and eleventh anal-fin ray), frontal squamation E-patterned ( vs. F-patterned), flank with striking iridescent colors in male, contrasting metallic blue to greenish blue on middle of flank with light purplish blue above anal fin and brownish golden on anterior dorsolateral portion of body ( vs. never a similar color pattern), flank with narrow pale red chevron-like oblique bars with anteriorly directed vertex ( vs. never a similar pattern), and no distinctive dark stripe along midline of flank ( vs. stripe present).

Description. Morphometric data in Table 5. Largest specimen 22.9 mm SL, male. Dorsal profile slightly convex from snout to end of dorsal-fin base, approximately straight to slightly concave on caudal peduncle. Ventral profile convex on head, weakly convex from anterior portion of venter to end of analfin base, nearly straight to gently concave along caudal peduncle. Body slender, subcylindrical anteriorly, slightly deeper than wide, to compressed posteriorly. Greatest body depth at level of pelvic-fin base.

Dorsal and anal fins weakly pointed to rounded in male, rounded in female. Caudal fin almost circular. Pectoral fin rounded, posterior margin on vertical just anterior to pelvicfin base. Tip of pelvic fin reaching urogenital papilla in male, and anus in female. Pelvic-fin bases in close proximity. Dorsal-fin origin on vertical through base of 8th or 9th anal-fin ray, and between neural spines of 17th and 19th vertebrae. Anal-fin origin between pleural ribs of 13th and 15th vertebrae. Dorsal-fin rays 10-12; anal-fin rays 14-5; caudal-fin rays 32-34; pectoral-fin rays 12-13; pelvic-fin rays 7.

Scales large, cycloid. Trunk scaled; head scaled except on its anteroventral surface. Body scales slightly extending over caudal-fin base; no scales on dorsal and anal fins. Frontal squamation E-patterned; E-scales not overlapping medially; scales arranged in circular pattern around central A-scale without exposed margins. Longitudinal series of scales 34- 35; transverse series of scales 10; scale rows around caudal peduncle 16. Contact organs absent. Supraorbital neuromasts 3 + 3. Six branchiostegal rays. Gill rakers of first branchial arch 1 + 7. Two vomerine teeth. Total vertebrae 29-30.

Coloration. Male: Side of body light metallic blue to light greenish blue, with narrow red chevron-like oblique bars with anteriorly directed vertex; rectangular dark red blotch on humeral region.Anterior dorsolateral portion of flank light brownish golden. Dorsum light yellowish brown, venter white. Opercular region light golden with two oblique dark red bars. Opercular and humeral red marks becoming brown when exposed to light. Infraorbital region and ventral surface of head white. Lower jaw gray. Iris light yellow. Dorsal fin yellow with five faint red bars. Anal fin pale yellow, base white to pale blue with six short red bars. Caudal fin yellow with four or five red bars on middle. Pelvic fin pale yellow. Pectoral fin yellowish hyaline.

Female: Side of body pale metallic greenish blue, with narrow red chevron-like oblique bars with anteriorly directed vertex; dark red blotch on humeral region. Anterior dorsolateral portion of flank pale golden. Dorsum light brown with gray blotches, venter white. Opercular region pale golden with two oblique dark red bars and blotches. Dark red marks on opercle and anterior portion of flank becoming black when exposed to light. Infraorbital region and ventral surface of head white. Lower jaw reddish gray. Iris light yellow. Dorsal fin dark yellow with three dark gray bars; broad dark gray distal stripe. Anal fin light yellow, base light blue with red dots; broad dark gray distal stripe. Caudal fin dark orangish red with four or five dark gray bars on middle; margins dark gray; black spot on subdorsal portion of caudal fin base. Pelvic fin pale blue, anterior margin dark gray. Pectoral fin hyaline.

Distribution. rio Verde drainage, rio Paraná basin, central Brazil ( Fig. 2 View Fig ). Rio Verde here assigned is a right affluent to the rio Paraná, situated between rio Correntes and rio Claro, Estado de Goiás.

Etymology. From the Latin rutilis (bright red, rufous) and caudus (tail), in reference to the diagnostic orangish red caudal fin in females.