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: 116-120
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Simpsonichthys marginatus ZBK Costa & Brasil, 1996: 94 ( type locality: Barro Alto, temporary pool near rio dos Patos, a tributary of rio Maranhao , rio Tocantins basin , Estado de Goiás, Brazil [approximately 15°00’S 49°00’W]; holotype: MNRJ 12440GoogleMaps ).
Brazil: Estado de Goiás, rio Tocantins drainage, rio Amazonas basin: MNRJ 12440, holotype, male, 23.1 mm SL; MNRJ 12441, 1 paratype; MZUSP 50163, 2 paratypes; UFRJ 3536, 7 paratypes; UFRJ 3537, 4 paratypes (c&s); UFRJ 3922, 1; Barro Alto, temporary pool close to rio dos Patos, rio Maranhao drainage ; W. J. E. M. Costa, G. C. Brasil, M. I. Landim & C. L. Moreira, 12- 13 Feb. 1996. MNRJ 18418, 12; pools close to rio dos Patos, Barro Alto ; D. F. Moraes & D. Lin, 10 Feb. 1999.
Differs from all congeners in possessing long pelvic fins in larger males, reaching base of 10th anal-fin ray (vs. reaching base of most anterior anal-fin ray). Distinguished from all other species of Hypsolebias by having flanks dark red, with blue bars anteriorly and vertical rows of blue dots posteriorly in males (vs. never a similar color pattern).
Morphometric data appear in Table 7. Largest specimen examined 37.9 mm SL. Dorsal profile slightly concave 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 both dorsal and anal fins pointed in males, rounded in females. Tip of both dorsal and anal fins with filamentous rays in males, tip of dorsal-fin filaments reaching vertical posterior to caudal fin. Caudal fin rounded. Pectoral fins elliptical. Posterior margin of pectoral fins reaching vertical through base of 9th analfin ray in males, and through base of 5th anal-fin ray in females. Tip of each pelvic fin reaching between base of 3rd and 10th anal-fin ray in males, and between urogenital papilla and base of 6th anal-fin ray in females. Pelvic-fin bases separated by interspace equal to pelvic-fin base in width. Anal-fin origin on vertical through base of 3rd dorsal-fin ray in males, and through dorsal-fin origin in females. Dorsal-fin origin between neural spines of vertebrae 6 and 7 in males, and neural spines of vertebrae 10 and 11 in females. Anal-fin origin between pleural ribs of vertebrae 7 and 8 in males, and pleural ribs of vertebrae 9 and 10 in females. Dorsalfin rays 20-22 in males, 15-17 in females; anal-fin rays 21-23 in males, 18-19 in females; caudal-fin rays 24; pectoral-fin rays 13-14; pelvic-fin rays 6.
Frontal squamation E-patterned; E-scales medially overlapped; no scale anterior to G-scale; supraorbital scales 2. Longitudinal series of scales 24-26; transverse series of scales 9-10; scale rows around caudal peduncle 12. Contact organ on each scale of anteroventral portion of flanks in males. Small papillate contact organs on inner surface of dorsalmost ray of pectoral fins in males.
Cephalic neuromasts: supraorbital 15, parietal 2, anterior rostral 1, posterior rostral 1, infraorbital 3 + 23- 24, preorbital 4-5, otic 1-2, post-otic 2, supratemporal 1, median opercular 1, ventral opercular 2, preopercular plus mandibular 30-32, lateral mandibular 8, paramandibular 1. One neuromast on center of each scale of lateral line. Two neuromasts on caudal-fin base.
Basihyal subtriangular, width about 55% of length in females, 75% in males; basihyal cartilage about 35% of total length of basihyal. Six branchiostegal rays. Second pharyngobranchial teeth 1-3. Gill-rakers on first branchial arch 3 + 10-11. Vomerine teeth absent. Dermosphenotic absent. Ventral process of posttemporal short. Total vertebrae 26-27.
Males. Sides of body brownish red, with 7-9 light greenish blue bars, posterior bars interrupted forming vertical rows of small spots.,Dorsal portion of head light purplish brown, scale margin red. Sides of head light purplish brown, metallic green on opercular region. Iris yellow with dark brown bar through center of eye. Unpaired fins brownish red, with light greenish blue dots; distal margin of dorsal and anal fin dark gray to black, bordered by light greenish blue subdistal stripe. Pelvic fins brownish red, with bright blue edge. Pectoral fins hyaline.
Females. Sides of body light brown, with 8-10 gray bars; one or two black blotches on anterocentral portion of flanks. Venter pale yellow. Head light brown, opercular region pale greenish blue. Iris light yellow, with dark brown bar through center of eye. Dorsal and anal fins hyaline, with dark gray spots. Caudal and pelvic fins gray. Pectoral fins hyaline.
Known only from the type locality region, rio dos Patos floodplains, rio Maranhão drainage, rio Tocantins basin, Estado de Goiás, central Brazil (Fig. 4).
Temporary pools within Mata de Galeria in the Cerrado.
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