Simpsonichthys auratus

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 : 79-80

Simpsonichthys auratus Costa & Nielsen. 2000

(Fig. 52)

Simpsonichthys auratus Costa & Nielsen, 2000: 8 ( type locality: temporary pool close to rio Taboca, a tributary of rio Paracatu, rio Sao Francisco basin, Lagoa Grande , Minas Gerais, Brazil [approximately 17º50’S 46º40’W; altitude about 680 m]; holotype: MZUSP 52912 ).

Material examined

Brazil: Estado de Minas Gerais, rio Paracatu drainage, rio São Francisco basin: MZUSP 52912 , holotype, male, 30.3 mm SL; MZUSP 52913 , 3 paratypes; UFRJ 4666 , 3 paratypes; UFRJ 4667 , 10 paratypes (c&s); UMMZ 234240 , 2 paratypes; UFRJ 4635 , 5; lagoa Grande, temporary pool close to rio Taboca ; W. J. E. M. Costa, D. Belote, G. Neves and D. Almeida, 10 Apr. 1998. UFRJ 4668 , 10 paratypes; UFRJ 4669 , 8; same locality ; D. T. B. Nielsen & A. Carletto, 1 May 1996.

Diagnosis

Similar to S. trilineatus and S. virgulatus , and distinguished from all other congeners by having the anterior portion of the flanks bright golden in males (vs. dark metallic yellow ochre) and by the presence of a humeral dark brown blotch in males (vs. absence). It differs from S. trilineatus and S. virgulatus by the following characters in combination: 3-4 black blotches on anterior portion of flanks in males (vs. 7-13), pectoral fins pale red (vs. hyaline), six pelvic-fin rays (vs. five), and caudal peduncle without conspicuous dark marks in males (vs. stripes or bars).

Description

Morphometric data appear in Table 4. Largest specimen examined 32.6 mm SL. Dorsal profile convex from snout 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 head side. 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. Short to moderately elongate filamentous rays on tip of dorsal and anal fin in males, tip reaching vertical through middle of caudal fin. Dorsalfin rays unbranched. Caudal fin rounded. Pectoral fins elliptical. Posterior margin of each pectoral fin reaching vertical through base of 6th anal-fin ray in males and urogenital papilla in females. Tip of each pelvic fin reaching base of 3rd anal-fin ray in males and base of 1st or 2nd anal-fin ray in females. Pelvic-fin bases in close proximity. Anal-fin origin on vertical through base of 2nd or 3rd dorsal-fin ray in males and 1st ray in females. Dorsal-fin origin between neural spines of vertebrae 7 and 9 in males and neural spines of vertebrae 11 and 13 in females. Anal-fin origin between pleural ribs of vertebrae 7 and 9 in males and pleural ribs of vertebrae 10 and 11 in females. Dorsal-fin rays 19-21 in males, 13-15 in females; anal-fin rays 18-20 in males, 16-17 in females; caudal-fin rays 25-28; pectoral-fin rays 13-14; pelvic-fin rays 6.

Frontal squamation A-patterned; E-scales slightly overlapping medially; no row of scales anterior to Fiscale; single supraorbital scale. Longitudinal series of scales 27; transverse series of scales 8; scale rows around caudal peduncle 12. Contact organ on each scale of anteroventral portion of flank in males. Small papillate contact organs on inner surface of dorsalmost ray of pectoral fin in males.

Cephalic neuromasts: supraorbital 13-14, parietal 2-3, anterior rostral 1, posterior rostral 1, infraorbital 2 + 19-20, preorbital 3, otic 2, post-otic 2, supratemporal 1, median opercular 1, ventral opercular 1, preopercular16-19, mandibular 12-13, lateral mandibular 6, paramandibular 1. One neuromast on each scale of lateral line. Two neuromasts on caudal-fin base.

Basihyal subtriangular, width about 60% of length; basihyal cartilage about 20% of total length of basihyal. Six branchiostegal rays. Second pharyngobranchial teeth 3. Gill-rakers on first branchial arch 3 + 10. Vomerine teeth absent. Dermosphenotic absent. Ventral process of posttemporal long. Total vertebrae 26- 28.

Coloration

Males. Anterior third of side of body golden, with three or four rounded black blotches, posterior two thirds light purplish brown, with dark purplish brown bars and six to eight horizontal rows of light greenish blue dots; venter golden. Sides of head golden, with small dark brown spots. Iris light yellow, with dark reddish brown bar through center of eye. Unpaired fins dark reddish brown, with white dots. Pelvic fins dark reddish brown, with white dot on base. Pectoral fins hyaline, ventral edge pale reddish orange.

Females. Sides of body light gray, with dark gray spots, often coalescent on posterior half of flank forming bars; venter pale golden; two rounded black blotches on anterocentral portion of flank. Opercular region pale golden. Iris light yellow, with gray bar through center of eye. Fins hyaline; small light blue spot on posterior margin of anal fin, just posterior to fin base.

Distribution

Rio Taboca floodplains, rio Paracatu drainage, middle rio São Francisco basin, Estado de Minas Gerais, Brazil (Fig. 1).

Habitat

Temporary pools in the Cerrado.