Simpsonichthys

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 : 7

Simpsonichthys Carvalho, 1959

Simpsonichthys Carvalho, 1959: 2 (type species: Simpsonichthys boitonei Carvalho; type by original designation).

Diagnosis

Differs from all other rivulids by having a small pointed process on the dorsal portion of the autopalatine (vs. process absent), and rays on the tip of the dorsal and anal fins unbranched in males (vs. branched), features hypothesized to be unambiguous synapomorphies of the genus by Costa (2006a).

Key to subgenera of Simpsonichthys

1a. No filamentous rays on posterior margin of anal fin in females; caudal fin rounded to subtruncate in males; bar on posterior portion of caudal peduncle never extending onto dorsal and ventral margins of caudal fin in males; most dorsal-fin rays unbranched in males ............................................................ 2

1b. Filamentous rays on posterior margin of anal fin in females; caudal fin lanceolate and asymmetric in males; bar on posterior portion of caudal peduncle extending onto dorsal and ventral margins of caudal fin in males; dorsal-fin rays branched, except for rays on anterior part of fin and rays on fin tip .... ............................................................................................................................................ Xenurolebias

2a(1a). Eyes placed dorsolaterally on head; anterior and posterior sections of supraorbital series of neuromasts continuous; anal fin hyaline in females .................................................................................................. 3

2b(1a). Eyes placed laterally on head; anterior and posterior sections of supraorbital series of neuromasts separated by interspace; anal fin pink in females.. ........................................................... Ophthalmolebias

3a(2a). Anterodistal portion of anal fin of females not distinctively thickened; small blue spot never present on posterior portion of anal fin in females .................................................................................................. 4

3b(2a). Anterodistal portion of anal fin of females distinctively thickened; small blue spot often present on posterior portion of anal fin in females ............................................................................... Hypsolebias

4a(3a). Pelvic fin and pelvic-girdle well-developed; red bars never present on opercle in males .................... Spectrolebias

4b(3a). Pelvic fin and pelvic-girdle vestigial or absent; red bars present on opercle in males ................. Simpsonichthys