Pituna xinguensis Costa & Nielsen, 2007

Wilson J. E. M. Costa, 2007, Taxonomy of the plesiolebiasine killifish genera Pituna, Plesiolebias and Maratecoara (Teleostei: Cyprinodontiformes: Rivulidae), with descriptions of nine new species., Zootaxa 1410, pp. 1-41 : 18-20

Pituna xinguensis Costa & Nielsen , new species

(Figs. 11-12)

Material examined. Holotype. UFRJ 6400 (male, 28.6 mm SL); Brazil: Estado do Pará: temporary pool in island, rio Xingu, in front of Altamira, 3°13’34.6”S, 52°12’26.1”W, altitude 39m; J. L. Diniz, 5 May 2003.

Paratypes. UFRJ 6401 (1 female, 30.1 mm SL) ; UFRJ 6402 (1 male, 26.5 mm SL; 1 female, 25.2 mm SL [c&s]); collected with holotype .

Diagnosis. Distinguished from all other congeners by the following combined morphological features: 25-29 scales in longitudinal series (vs. 23-24), pectoral fins with vertical rows of small dark gray spots or dark gray bars in males (vs. pectoral fins without dark marks), frontal squamation F-patterned (vs. D-patterned), anterior section of supraorbital series of neuromasts continuous (vs. interrupted), dark marks on flanks mainly obliquely arranged in females (vs. mainly longitudinally or irregularly arranged), 1 + 1+ 17-21 + 1 infraorbital neuromasts (vs. 1 + 1+ 13-17 + 1), caudal-fin rays 26-27 (vs. 28-31), and oblique rows of dark brown dots forming oblique bars on flanks in females (vs. never forming bars).

Description. Morphometric data appear in Table 2. Largest male examined 28.6 mm SL; largest female examined 30.1 mm SL. Dorsal profile gently convex from snout to end of dorsal-fin base, approximately straight on caudal peduncle. Ventral profile slightly convex from lower jaw to anal-fin origin, nearly straight along caudal peduncle. Body slender, subcylindrical, slightly deeper than wide, greatest body depth at level of pelvic-fin base. Jaws short, snout blunt.

Dorsal and anal fins pointed in both sexes, but longer and reaching to vertical through caudal-fin base in males. Caudal fin rounded. Pectoral fins rounded, their posterior margin reaching vertical between pelvic-fin base and anus in males, through pelvic-fin base in females. Pelvic fins short, slightly pointed, tip reaching base of 5th anal-fin ray in males, and base of 3rd or 4th anal-fin ray in females. Pelvic-fin bases medially in close proximity. Dorsal-fin origin at vertical through base of 10th or 11th anal-fin rays, between neural spines of vertebrae17 and 19. Anal-fin origin between pleural ribs of vertebrae 11 and 13. Dorsal-fin rays 9-10; anal-fin rays 14-15; caudal-fin rays 26-27; pectoral-fin rays 14-15; pelvic-fin rays 7.

Scales large, cycloid. Body and head entirely scaled, except on anteroventral surface of head. No scales on dorsal and anal-fin bases. Scales extending onto anterior 50 % of caudal fin. Frontal squamation F-patterned, frontal scales circularly arranged around A-scale without free margins; E-scales not overlapping; row of scales anterior to H-scale; supraorbital scales 6. Longitudinal series of scales 26; transverse series of scales 8; scale rows around caudal peduncle 16. Two or three contact organs on posterior margin of each scale of flank. No contact organs on fin rays.

Cephalic neuromasts: supraorbital 5-7 + 4-5, parietal 2, anterior rostral 1, posterior rostral 1, infraorbital 1 + 1 + 15 + 1, preorbital 3-4, otic 1-2, post-otic 2, supratemporal 1, median opercular 1, ventral opercular 2, preopercular 10, mandibular 8, lateral mandibular 3, paramandibular 1. One neuromast per scale of lateral line. Two neuromasts on caudal-fin base.

Basihyal subtriangular, greatest width about 55 % of length; basihyal cartilage about 35 % of total length of basihyal. Six branchiostegal rays. Second pharyngobranchial teeth 2. Gill-rakers on first branchial arch 1 + 9. Vomerine teeth 1. Dermosphenotic present. Ventral process of posttemporal short. Total vertebrae 28-29.

Coloration. Males. Sides of body reddish brown, with oblique rows of small golden spots; vertically elongated, metallic blue blotch on humeral region. Dorsum light brown. Venter light gray. Sides of head light greenish golden, scale borders purplish brown; dark gray to black infraorbital bar, adjacent to narrow preorbital light gray bar. Jaws purplish brown. Iris orangish yellow, with dark brown bar through center of eye. Exposed part of branchiostegal membrane dark gray. Dorsal fin bright greenish blue, distal portion of median rays red, posterior portion of fin yellow, with 3 short orangish brown bars. Anal fin dark orangish brown, with row of 5-6 yellow spots along fin base and posterior margin, and two transverse rows of pale greenish yellow spots, sometimes fused to form stripes, on middle and subdistal portion of fin. Caudal fin dark brown. Pectoral fins hyaline, with 4-6 transverse series of alternating, small light greenish yellow and dark gray spots. Pelvic fins orangish brown, with pale yellow spots on basal portion.

Females. Sides of head and trunk light gray, with oblique rows of small dark brown spots, often coalesced to form oblique bars. Dorsum light brown. Venter light gray. Opercular region pale greenish golden. Dark gray infraorbital bar, adjacent to narrow preorbital light gray bar. Jaws dark gray. Iris yellow, with dark brown bar through center of eye. Unpaired fins hyaline, with faint small brown spots on basal portion. Paired fins hyaline.

Etymology. The name xinguensis is an allusion to the occurrence of the new species in the rio Xingu.

Distribution and habitat. Known only from the type locality, a temporary swamp on a rio Xingu island near Altamira (Fig. 1), Brazilian Amazonian forest.