Simpsonichthys notatus

Wilson J. E. M. Costa & Gilberto C. Brasil, 2004, Simpsonichthys radiosus sp. n. (Teleostei: Cyprinodontiformes: Rivulidae): a new annual killifish from the upper Rio Tocantins basin, central Brazil., Zootaxa 737, pp. 1-7 : 5-6

Key to species of the S. notatus group

1 Dorsal and anal fins pointed in male; 3 + 8-10 gill-rakers on first branchial arch; never bars on caudal fin in male; flank with rounded dark gray spots and without iridescent marks in female ............................................................................................................. 2

- Dorsal and anal fins rounded in male; 4 + 13 gill-rakers on the first branchial arch; caudal fin with blue bars in male; flank with dark gray bars, silver bars on median portion and anterocentral black blotch with wide bluish silver to light golden contour in female ....................................................................................................................... S. ocellatus

2 Black blotch on anterocentral portion of flank in male.................................................4

- No black blotch on flank in male..................................................................................3

3 Distal dark gray to black stripe on anal fin in male; bright blue spots alternating with black interspace on dorsal-fin base in male; caudal fin brownish red in male; anal-fin origin between pleural ribs of vertebrae 7 and 9 in male, and 9 and 10 in female......... ........................................................................................................................ S. stellatus

- No distal stripe on male anal fin; bright blue dots on entire dorsal fin in male; caudal fin brownish yellow in male; anal-fin origin between pleural ribs of vertebrae 9 and 10 in male, and 11 and 12 in female......................................................................... S. rufus

4 Anal fin with bright dots and no bars in male; no distal stripe on dorsal fin in male ... 6

- Anal fin with oblique dark gray bars and no bright dots in male; bright blue stripe on distal edge of dorsal fin in male....................................................................................5

5 Caudal fin with blue dots and marginal blue stripe on dorsal half in male; blue dots over entire flank in male; tip of pectoral fin reaching between base of 5th and 7th analfin rays in male................................................................................................ S. notatus

- Caudal fin with light blue stripes parallel to fin rays, alternating with subdistal rounded light blue spots in male; tip of pectoral fin reaching between base of 1st and 3rd anal-fin rays in male................................................................................ S. radiosus

6 Anterior portion of flank bright golden in male; humeral dark brown blotch in male ... ...................................................................................................................................... 7

- Anterior portion of flank dark metallic yellow ochre in male; no humeral marks.......... ........................................................................................................................... S. similis

7 Five pelvic-fin rays; three purplish brown stripes on posterior portion of flank in male; no dark brown blotch on anteroventral portion of flank in male................ S. trilineatus

- Six pelvic-fin rays; purplish brown bars on posterior portion of flank in male; dark brown blotch on anteroventral portion of flank in male.................................. S. auratus

Discussion

Monophyly of the S. notatus species group is supported by a single synapomorphy, the A- pattern frontal squamation (Costa, 2003). This pattern differs markedly from the pattern of other congeners by the median A-frontal scale having all margins free, while in other species the whole scale margin is free in the paired E-frontal scale. The A-pattern never occurs in genera closely related to Simpsonichthys such as Cynolebias Steindachner , Megalebias Costa , Austrolebias Costa , Cynopoecilus Regan , Campellolebias Vaz-Ferreira & Sierra , and Leptolebias Myers (Costa, 1998, 2001, 2002), thus considered an unambiguous synapomorphy of the S. notatus species group (Costa, 2003). However, relationships among species of the S. notatus group are still not clear at the present, with some potentially informative characters having great variability in outgroups. An exception is the distal blue stripe on the dorsal fin in males uniquely shared by S. notatus and S. radiosus , the only two species of the S. notatus group endemic to the upper Rio Tocantins basin, suggesting a sister group relationship between these two taxa. However, since a phylogenetic analysis is beyond the scope the present study, variability of all character states necessary to erect hypotheses of relationships of S. radiosus with other congeners is not discussed here.