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: 68-70
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Simpsonichthys radiosus ZBK Costa & Brasil, 2004: 1 ( type locality: rio Crixas floodplains, about 6 km from the confluence with rio Parana , Formosa , Estado de Goiás, Brazil, about 15°20’S 47°20’W, altitude about 800 m; holotype: UFRJ 6017GoogleMaps ).
Brazil: Estado de Goiás, rio Tocantins drainage, rio Amazonas basin: UFRJ 6017, holotype, male, 23.4 mm SL; UFRJ 6018, 9 paratypes; UFRJ 6019, 6 paratypes (c&s); UFRJ 6020, 6 paratypes; UFRJ 6021, 5 paratypes; Formosa, rio Crixas floodplains, about 6 km from the confluence with rio Parana , about 15°20’S 47°20’W; altitude about 800 m; G. C. Brasil, 10 May 2004.GoogleMaps
Distinguished from all congeners by possessing a unique color pattern on caudal fin in males, consisting of three to five light blue stripes crossing fin, parallel to fin rays, alternating with subdistal rounded light blue spots (vs. never a similar color pattern).
Morphometric data appear in Table 4. Largest specimen examined 27.6 mm SL. Dorsal profile straight to slightly convex on head, convex from nape to end of dorsal-fin base, approximately straight on caudal peduncle. Ventral profile convex from lower jaw to end of anal-fin base, nearly straight on caudal peduncle. Body moderately deep, compressed, greatest body depth at level of pelvic-fin base. Eye positioned on dorsal portion of side of head. Snout blunt. Urogenital papilla cylindrical and short in males, pocket-shaped in females.
Tip of dorsal fin slightly pointed in both sexes, tip of anal fin slightly pointed in males, rounded in females. Tip of dorsal and anal fins with minute filamentous rays in males. Median dorsal-fin rays branched, anterior and posterior rays unbranched. Caudal fin subtruncate. Pectoral fins elliptical. Posterior margin of each pectoral fin reaching vertical between base of 1st and 3rd anal-fin rays in males, between anus and urogenital papilla in females. Tip of each pelvic fin reaching base of 2nd or 3rd anal-fin ray in males, between urogenital papilla and base of 1st anal-fin ray in females. Pelvic-fin bases in close proximity. Dorsal-fin origin anterior to anal-fin origin; anal-fin origin on vertical between base of 4th and 6th dorsal-fin rays in males, between base of 1st and 3rd dorsal-fin rays in females; dorsal and anal-fin origins between neural spines of 7th and 8th vertebrae in males, 9th and 10th vertebrae in females. Dorsal-fin rays 23-26 in males, 17-19 in females; anal-fin rays 21-23 in males, 18-22 in females; caudal-fin rays 25-26; pectoral-fin rays 12-13; pelvic-fin rays 5-6.
Frontal squamation A-patterned; E-scales medially overlapped; no scale anterior to G-scale. Longitudinal series of scales 25-27; transverse series of scales 10; scale rows around caudal peduncle 12. Minute contact organ on each scale of anteroventral portion of flank in males. Small papillate contact organs on dorsal surface of dorsalmost pectoral-fin ray in males.
Cephalic neuromasts: supraorbital 3-4 + 8-10, parietal 2-4, anterior rostral 1, posterior rostral 1, infraorbital 2 + 17-20, preorbital 3, otic 2, post-otic 2-3, supratemporal 1, median opercular 1, ventral opercular 1, preopercular13-14, mandibular 10-12, lateral mandibular 5-6, paramandibular 1. One neuromast on center of each scale of lateral line. Two neuromasts on caudal-fin base.
Basihyal subtriangular, width about 85% of length; basihyal cartilage about 30% of total length of basihyal. Six branchiostegal rays. Second pharyngobranchial teeth 3. Gill-rakers on first branchial arch 3 + 9. Vomerine teeth absent. Dermosphenotic absent. Ventral process of posttemporal long. Total vertebrae 27- 28.
Males. Sides of body light purplish brown to reddish brown on anteroventral portion, with 8-9 gray bars, and few pale blue dots irregularly arranged on dorsal portion; black rounded blotch on lateral midline, overlapping third bar, at vertical through dorsal-fin origin. Opercular region golden, with light blue spots. Iris light yellow, with dark brown bar. Dorsal fin reddish brown, with subbasal row of light blue spots, and similar slightly smaller spots on posterior region; distal bright blue stripe with black dorsal outline. Anal fin reddish brown, with five faint gray bars. Caudal fin dark reddish brown, with 3-5 light blue stripes parallel to fin rays, alternating with subdistal rounded light blue spots. Pectoral fins hyaline. Pelvic fins reddish brown, tip dark gray.
Females. Sides of body light purple, with small dark gray spots; spot on anterocentral portion of flank black. Opercular region light golden, with gray dots. Iris light yellow, with dark gray bar. Unpaired fins hyaline, with small gray spots on basal portion; small light blue spot on posterior portion of anal fin. Paired fins hyaline.
Rio Crixás floodplains, rio Paranã drainage, upper rio Tocantins basin, central Brazil (Fig. 1).
Temporary pools in the Cerrado.
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