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: 64-66
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Simpsonichthys nielseni ZBK Costa, 2005: 58 ( type locality: temporary pool in Pirapora, rio Sao Francisco floodplains , 17°21’59.6”S 44°56’32.3”W, altitude 500 m, Estado de Minas Gerais, Brazil; holotype: UFRJ 6060GoogleMaps ).
Brazil: Estado de Minas Gerais, rio São Francisco floodplains: UFRJ 6060, holotype, male, 37.0 mm SL; UFRJ 6061, 7 paratypes; UFRJ 6062, 5 paratypes (c&s); MCP 37306, 2 paratypes; temporary pool in Pirapora , 17°21’59.6”S 44°56’32.3”W; altitude 500 m; W. J. E. M. Costa & C. P. Bove, 22 Jan. 2005.GoogleMaps
Distinguished from all other congeners by having six or seven light greenish yellow stripes on caudal fin in males, parallel to fin rays, between fin base and fin margin, each stripe distally terminating in sharp tip and alternating with elongate spots of the same color on subdistal portion of fin.
Morphometric data appear in Table 4. Largest specimen examined 40.5 mm SL. Dorsal profile convex from snout to end of dorsal-fin base, nearly straight on caudal peduncle. Ventral profile convex from lower jaw to end of anal-fin base, approximately straight on caudal peduncle. Body moderately deep, compressed, greatest body depth at level of pelvic-fin base. Eye positioned on dorsal portion of head side. Snout blunt. Urogenital papilla cylindrical and short in males, pocket-shaped in females.
Tip of dorsal fin pointed. Tip of anal fin pointed in males, rounded in females. Short filamentous rays on tip of dorsal and anal fins in males; tip of filaments reaching vertical through caudal-fin base. Anterior and posterior rays of dorsal fin, including rays on tip of fin, unbranched; median rays branched. Caudal fin subtruncate in males, rounded in females. Pectoral fins elliptical. Posterior margin of each pectoral fin reaching vertical between base of 4th and 6th anal-fins ray in males, and through pelvic-fin base in females. Tip of pelvic fin reaching between base of 3rd and 4th anal-fin rays in males, and between urogenital papilla and base of 1st anal-fin ray in females. Pelvic-fin bases medially in contact. Dorsal-fin origin anterior to anal-fin origin in males, anal-fin origin on vertical between base of 2nd and 4th dorsal-fin rays; dorsal-fin origin slightly anterior to slightly posterior to anal-fin origin in females. Dorsal-fin origin between neural spines of vertebrae 8 and 9 in males, between neural spines of vertebrae 9 and 11 in females. Anal-fin origin between pleural ribs of vertebrae8 and 9 in males, between pleural ribs of vertebrae 9 and 11 in females. Dorsal-fin rays 21-22 in males, 16-17 in females; anal-fin rays 19-21 in males, 17-18 in females; caudal-fin rays 25-27; pectoral-fin rays 12-13; pelvic-fin rays 6.
Frontal squamation usually A-patterned; E-scales medially overlapping; no scale anterior to G-scale. Longitudinal series of scales 26-27; transverse series of scales 9-10; scale rows around caudal peduncle 12- 13. Minute contact organ on each scale of anteroventral portion of flank in males. Small papillate contact organs on upper surface of dorsalmost ray of pectoral fins in males.
Cephalic neuromasts: supraorbital 13, parietal 2-3, anterior rostral 1, posterior rostral 1, infraorbital 2-3 + 19-21, preorbital 3, otic 2, post-otic 1-2, supratemporal 1, median opercular 1, ventral opercular 2, preopercular plus mandibular 26-27, lateral mandibular 4-5, paramandibular 1. One neuromast on center of each scale of lateral line. Two neuromasts on caudal-fin base.
Basihyal subtriangular, width about 60% of length; basihyal cartilage about 35% of total length of basihyal. Six branchiostegal rays. Second pharyngobranchial teeth 3. Gill-rakers on first branchial arch 2 + 10. Vomerine teeth absent. Dermosphenotic absent. Ventral process of posttemporal long. Total vertebrae 27.
Males. Sides of body dark yellow ochre, with 9-11 dark purplish gray bars and light blue dots; venter yellowish white. Sides of head yellow ochre to bright greenish blue on opercular and infraorbital region. Scales on posterodorsal of head side and anterodorsal portion of flanks red. Iris light purplish yellow, with dark brown bar through center of eye. Dorsal fin greenish brown; greenish yellow elongate spots forming short bars on basal region, alternating with dark gray to black elongate spots; row of greenish blue short lines along distal margin of fin. Anal fin greenish brown, with light greenish yellow bars. Caudal fin greenish yellow, with greenish blue margin; light greenish yellow stripes, parallel to fin rays, diverging from fin base to all fin margins, each stripe distally terminating in sharp tip, and alternating with elongate spots of identical color on subdistal portion of fin. Pelvic fins purplish brown. Pectoral fins hyaline.
Females. Sides of body light yellowish brown, with dark gray spots; spots above anal-fin base sometimes elongate, forming short bars; 2-3 spots on anterocentral portion of flank black; venter pale golden. Opercular region greenish golden. Iris light yellow, with gray bar through center of eye. Unpaired fins hyaline, with black small spots on basal region; small light blue spot on posterior margin of anal fin, just posterior to fin base. Paired fins hyaline.
Middle rio São Francisco floodplains, Pirapora, Estado de Minas Gerais, Brazil (Fig. 1).
Temporary pools in the Cerrado.
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