Rivulus, Poey, 1860

Costa, Wilson J. E. M., 2005, Seven new species of the killifish genus Rivulus (Cyprinodontiformes: Rivulidae) from the Paraná, Paraguay and upper Araguaia river basins, central Brazil, Neotropical Ichthyology 3 (1), pp. 69-82 : 70-71

Key to the species of Rivulus from the Paraná-Paraguay river basins and adjacent headwaters

1. Never distinctive stripe along midline; often red bars on caudal fin in male (except in R. pinima and R. egens ); frontal squamation usually E-patterned (except in R. litteratus ); flank with intense iridescent colors in male, usually 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 ....................................................................................... 5

1'. Always distinctive stripe along midline, more conspicuous when exposed to light, but also visible in preserved specimens; never red bars on caudal fin; frontal squamation F-patterned, except in a few specimens of R. dapazi with E-patterned squamation; iridescent colors present or not, when present not intense, whole flank metallic green ....................................................................................... 2

2. Scales on longitudinal series 30-32; oblique rows of red dots on flank; anal fin never with orange distal stripe; caudal-fin never with entire margin dark orange with black ventral outline ................................................................ 3

2'. Scales on longitudinal series 34-35; oblique red bars on flank; anal fin with dark orange distal stripe in male; entire caudal-fin margin dark orange with black ventral outline in male .................................................................. R. dapazi

3. Caudal-fin rays 27-29; never anal fin blue with red bars; caudal fin with distinctive colors at least on dorsal and anal fin margins in male .................................................. 4

3'. Caudal-fin rays 29-31; whole anal fin blue with oblique red bars in both sexes; caudal fin yellow, without distinctive colors on margins in male ........................ R. cyanopterus

4. Gill rakers on first arch 1+6; narrow orange stripe on anterior portion of dorsal and ventral margins of caudal fin in male ................................................................... R. rossoi

4'. Gill rakers on first arch 1+8; white stripe on entire caudal fin margin in male......................................... R. punctatus

5. Frontal squamation E-patterned ..................................... 6

5'. Frontal squamation F-patterned ................... R. litteratus

6. 29-32 scales on the longitudinal series ......................... 11

6'. 32-36 scales on the longitudinal series ...........................7

7. 10-12 dorsal-fin rays .......................................................8

7'. 8-10 dorsal-fin rays ............................................ R. pictus

8. Ventral portion of caudal fin with a distinctive dark yellowish gray zone .................................................................. 9

8'. Ventral portion of caudal fin without a distinctive dark colored zone ...................................................................... 10

9. Dorsal and anal fins rounded in male; tip of pelvic fin reaching between urogenital papilla and base of first anal-fin ray in male; never oblique red bars on flank; no dark marks on opercular and humeral regions; red dots or no red marks on caudal fin in males, dark gray spots in female ......................................................................... R. pinima

9'. Dorsal and anal fins pointed in male; tip of pelvic fin reaching between base of second and fourth anal-fin rays in male; oblique red bars on flank; dark reddish brown marks on opercular and humeral regions; broad bars on caudal fin, red in males, dark gray in female ........................................................................ R. vittatus

10. Dorsal-fin origin at vertical between base of eighth and ninth anal-fin ray; flank light metallic blue with narrow red chevron-like oblique bars in males; caudal fin dark orangish red in females ........................................... R. rutilicaudus

10'. Dorsal-fin origin at vertical between base of seventh and eighth anal-fin ray; flank intense metallic blue with broad red chevron-like oblique bars in males; caudal fin pale yellow in females ................................................. R. scalaris

11. 11-12 pectoral-fin rays; caudal fin with narrow red bars in males, and dark gray bars in females ............. R. apiamici

11'. 13-14 pectoral-fin rays; caudal fin without red marks in males, and with vertical rows of dark gray spots in females ........................................................................... R. egens