Simpsonichthys (Spectrolebias)

Wilson J. E. M. Costa, 2007, Taxonomic revision of the seasonal South American killifish genus Simpsonichthys (Teleostei: Cyprinodontiformes: Aplocheiloidei: Rivulidae)., Zootaxa 1669, pp. 1-134 : 42

Subgenus Spectrolebias Costa & Nielsen, 1997

Spectrolebias Costa & Nielsen, 1997: 258 (type species Spectrolebias semiocellatus Costa & Nielsen, by original designation; first proposed as a genus).

Diagnosis

Distinguished from all other cynolebiatins by two unambiguous synapomorphies (Costa, 2006a): a long (vs. short) hyomandibula and a narrowed (vs. wide) proximal tip of the fourth ceratobranchial.

Included species

Simpsonichthys chacoensis (Amato), S. semiocellatus (Costa & Nielsen), S. filamentosus Costa, Barrera & Sarmiento, S. costai (Lazara), and S. reticulatus Costa & Nielsen.

Distribution

Southern Amazonian river drainages, including rio Madeira, Xingu, Araguaia and Tocantins, and Paraguayan Chaco, río Paraguay basin (Figs. 1 and 4).

Key to species of the subgenus Spectrolebias

1a. Dorsal fin rounded in males; dark suborbital and postorbital bars........................................................2

1b. Dorsal fin pointed in males; no bars on head........................................................................................3

2a(1a). Dorsal-fin rays 23-25 in males, 13-15 in females; flank greenish blue with dark red crimson scale margins in males................................................................................................................. S. reticulatus

2b(1a). Dorsal-fin rays 21-23 in males, 16-19 in females; flank dark brown to black with light blue dots in males.......................................................................................................................................... S. costai

3a(1b). Anal-fin rays 23-25 in males; flanks light orange to translucent, unpaired fins pale red in males........................................4

3b(1b). Anal-fin rays 26-28 in males; flanks and unpaired fins dark bluish gray in males............................... S. chacoensis

4a(3a). Frontal squamation E-patterned; anal fin pointed and with long filaments in males; no black spot on anal fin in males.............................................................................................................. S. filamentosus

4b(3a). Frontal squamation F-patterned; anal fin rounded and without filaments in males; black and blue spot on posterior portion of distal edge of anal fin in males................................................. S. semiocellatus