Plesiolebias filamentosus Costa & Brasil, 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 : 27-29

Plesiolebias filamentosus Costa & Brasil , new species

(Figs. 18-19)

Plesiolebias xavantei non P. xavantei (Costa, Lacerda & Tanizaki) ; Costa, 1998c: 330 (misidentification of specimens from Itaguatins, Tocantins, Brazil).

Material examined. Holotype. UFRJ 6367 (male, 18.3 mm SL); Brazil: Estado do Tocantins: Sampaio, temporary pool in rio Tocantins floodplains, about 1.5 km from the left river bank, 5°16’58”S, 47°53’30”W, altitude102 m; G. C. Brasil, 3 June 2000.

Paratypes. Brasil: Estado do Tocantins: UFRJ 5135 (6 males, 16.7-19.6 mm SL, 7 females, 16.8-17.5 mm SL) ; UFRJ 6368 (3 males, 16.1-18.9 mm SL [c&s]); collected with holotype . UFRJ 4089, 3 males, 17.5-19.9 mm SL, 8 females, 16.9-20.7 mm SL; Itaguatins, temporary pool near left bank of rio Tocantins, about 5°30’S, 47°30’W, altitude about 130 m; G. C. Brasil, 20 Apr 1997 .

Diagnosis. Distinguished from all its congeners by the following morphological features in combination: filamentous ray on each pelvic fin in males (vs. filamentous ray absent); pelvic-fin rays 8 (vs. 7); eye yellow in males (vs. bright green); flanks with oblique black bars in males (vs. black bars absent); red stripe on anterior portion of flanks not anteriorly reaching orbit in males (vs. red stripe reaching orbit or absent); basal portion of dorsal fin red in males (vs. with transverse rows of dark red and white spots); a black spot on posterior portion of anal fin in males (vs. black spot absent); body depth 28.6-30.8 % SL in males, 26.4-29.3 % SL in females (vs. 23.2-25.7 % SL in males, 23.0-26.0 % SL in females); oblique rows of bright dots on flank in males (vs. sparse bright dots on flank); 4 white bars on basal portion of anal fin in males (vs. 3); a black bar on preopercle (vs. black bar absent); dorsal fin-origin in vertical between base of 5th and 6th anal-fin rays (vs. between base of 3 rd and 5th or between base of 7th and 8th anal-fin rays); 15-16 anal-fin rays (vs. 17-18); red pigmentation restricted to basal third of dorsal fin in males (vs. extending to basal two thirds of dorsal fin); small white spots on dorsal-fin base in males (vs. white bars).

Description. Morphometric data given in Table 2. Largest male examined 19.9 mm SL, largest female examined 20.7 mm SL. Dorsal profile slightly convex from snout to end of dorsal-fin base, approximately straight on caudal peduncle. Ventral profile gently convex from lower jaw to end of anal-fin base, nearly straight on caudal peduncle. Body moderately slender, compressed. Greatest body depth at level of pelvic-fin base. Jaws short, snout blunt.

Tip of both dorsal and anal fins rounded. Caudal fin rounded. Pectoral fins elliptical, posterior margin reaching vertical through base of 2nd anal-fin ray in male, through anus in female. Pelvic fins pointed in males, terminating in long filament, with tip reaching between base of 10th and 13th anal-fin ray; tip of each pelvic fin reaching base of 2nd anal-fin ray in females. Pelvic-fin bases medially united. Dorsal-fin origin on vertical through base of 7th or 8th anal-fin ray, and between neural spines of 10th and 12th vertebrae. Anal-fin origin between pleural ribs of 9th and 11th vertebrae. Dorsal-fin rays 11-13; anal-fin rays 15-16; caudal-fin rays 23- 25; pectoral-fin rays 12; pelvic-fin rays 8.

Scales large, cycloid. Body and head entirely scaled, except anterior ventral surface of head. Body squamation extending onto anterior 20 % of caudal fin; no scales on dorsal and anal-fin bases. Frontal squamation G-patterned; E-scales overlapping medially; scales arranged in regular transverse pattern. Two supraorbital scales. Longitudinal series of scales 23; transverse series of scales 8; scale rows around caudal peduncle 12. Three to five minute contact organs on posterior margin of each scale of ventral portion of flank in males.

Cephalic neuromasts: supraorbital 6 + 5, parietal 2, anterior rostral 1, posterior rostral 1, infraorbital 1 + 20-25 + 1, preorbital 3, otic 1, postotic 2, supratemporal 1, median opercular 1, ventral opercular 2, preopercular2 + 8-10, mandibular 4 + 2, lateral mandibular 2. One neuromast on center of each scale of lateral line of trunk. Two neuromasts on caudal-fin base.

Basihyal subtriangular, narrow, width about 30 % of length; basihyal cartilage about 30 % of basihyal length. Five branchiostegal rays. Five teeth on second pharyngobranchial. Gill-rakers of first branchial arch 1 + 8. No vomerine tooth. Ventral process of posttemporal minute or absent. Total vertebrae 24-25.

Coloration. Males: Sides of body pale pink, with 8-9 oblique dark purplish to black bars, alternating with two or three oblique rows of white dots on anterior half of flanks and with single similar row on posterior portion of flanks; red stripe on anterior portion of laterodorsal region of trunk, between vertical through posterior margin of opercle and vertical just posterior to pelvic-fin base. Dorsum light purplish brown. Venter pinkish white, with transverse dark gray marks. Sides of head pale pink, with oblique dark gray oblique bars; opercular region golden with two dark gray to black bars, anterior bar adjacent to posterior orbital margin, posterior bar on preopercle, posterior edge on opercle black. Jaws pale pink. Iris yellow, with black bar through center of eye. Dorsal fin red on basal third, with three white dots on fin base, hyaline on distal two thirds. Anal fin reddish black, distal third dark gray with blue iridescence; four white oblique bars on basal two thirds of fin. Caudal fin grayish hyaline to reddish hyaline on basal portion, with transverse rows of faint light gray dots. Pectoral fins hyaline. Pelvic fins black, with two white bars, anterior bar near anterior margin of fin and posterior bar on posterior margin; blue iridescence on anterior margin of each fin.

Females: Sides of body light brownish gray, with 8-9 oblique rows of dark brown closely positioned dots. Dorsum light brown. Venter white. Sides of head light brown, pale greenish yellow on opercle. Jaws gray. Iris pale yellow, with gray bar through center of eye. Fins hyaline.

Distribution and habitat. Temporary pools in the southeastern portion of the Amazonian forest, middle rio Tocantins floodplains, between Itaguatins and Sampaio, Estado do Tocantins, Brazil (Fig. 13).

Etymology. From the Latin filamentosus (filamentous), an allusion to the long filamentous pelvic-fin ray in male.