Cyphocharax meniscaprorus Vari 1992

Cyphocharax meniscaprorus

DIAGNOSIS.—Cyphocharax meniscaprorus is distinguished from its congeners by the combination of 29 to 32 lateral-line scales to the hypural joint, the complete poring of the lateral line in all but juveniles, the 30 to 32, typically 31 vertebrae, the relative body depth (0.33–0.39 of SL), the relative depth of the caudal peduncle (0.12–0.14 of SL), the relative length of the postorbital portion of head (0.34–0.39 of HL), the relative length of the head (0.31–0.34 of SL), the relative width of the orbit (0.32–0.36 of HL), the absence of multiple series of longitudinal dark stripes or small dark spots in longitudinal rows on the body, the absence of a discrete patch of dark pigmentation on the dorsal fin, the presence of a triangular patch of dark pigmentation on the midlateral surface of the caudal peduncle not preceded by 4 or 5 large midlateral dark spots on the body, the absence of a stripe of dark pigmentation across the middle rays of the caudal fin in moderate to large-sized specimens, the lack of a reticulate pattern on the body in adults, the relatively rotund anterior dorsal profile of the head, and the possession of 9 branched dorsal-fin rays.

DESCRIPTION.—Body moderately elongate, more so in larger specimens; moderately compressed laterally in all examined specimens. Dorsal profile of head distinctly convex from margin of upper lip to vertical line through posterior nostril, straight or very slightly convex from that line to posterior terminus of head. Dorsal profile of body smoothly curved from tip of supraoccipital spine to origin of dorsal fin; straight and slightly posteroventrally slanted at base of dorsal fin, very genüy convex from base of last dorsal-fin ray to caudal peduncle. Dorsal surface of body with barely distinct median keel anterior to dorsal fin, smoothly rounded transversely posterior to fin. Ventral profile of body gently curved from tip of lower jaw to caudal peduncle. Prepelvic region barely flattened transversely, with median series of scales comparable in size to those on adjoining surfaces of body. Obtuse median keel posterior to pelvic-fin origin; secondary keels on the postpelvic portion of body not evident.

Greatest body depth at origin of dorsal fin, depth 0.33–0.39 [0.33]; snout tip to origin of dorsal fin 0.51–0.55 [0.52]; snout tip to origin of anal fin 0.82–0.87 [0.84]; snout tip to origin of pelvic fin 0.57–0.62 [0.57]; snout tip to anus 0.79–0.86 [0.80]; origin of dorsal fin to hypural joint 0.51–0.55 [0.55]. Distal margin of dorsal fin rounded; last unbranched and first branched dorsal-fin rays approximately three and one-half times length of ultimate ray. Distal margin of pectoral-fin profile somewhat pointed; length of pectoral fin 0.20–0.23 [0.22], extending to slightly beyond vertical line through origin of dorsal fin, about two-thirds of distance to origin of pelvic fin. Distal margin of pelvic fin slightly rounded; length of pelvic fin 0.22–0.26 [0.22], reaching nearly to anus in all examined specimens, falling distinctly short of origin of anal fin. Caudal fin forked. Adipose fin well developed. Distal margin of anal fin emarginate, anteriormost branched rays approximately two and one-half times length of ultimate ray. Least depth of caudal peduncle 0.12–0.14 (0.12 and 0.14 rare) [0.13].

Head profile rounded anteriorly, but pointed overall; head length 0.31–0.34 [0.31]; upper jaw longer than lower, mouth barely subterminal; upper jar somewhat fleshy; snout length 0.29–0.35 [0.30]; nostrils of each side very close, anterior irregularly circular, posterior crescent-shaped with aperture closed by thin flap of skin separating nares; orbital diameter 0.32–0.36 [0.35]; adipose eyelid present but poorly developed, with broad opening over eye; length of postorbital portion of head 0.34–0.39 [0.36]; gape width 0.23–0.27 [0.27]; interorbital width 0.40–0.45 [0.41].

Pored lateral-line scales from supracleithrum to hypural joint 29 to 32 [32]; all scales of lateral line pored, canals in lateral-line scales straight; 3 or 4 series of pored scales extend beyond hypural joint onto caudal-fin base; 5 or 5 (5 rare) [5] scales in transverse series from origin of dorsal fin to lateral line; 4 or 5 (5 rare) [4] scales in transverse series from lateral line to origin of anal fin.

Dorsal-fin rays ii,9 [ii,9]; anal-fin rays ii,7 or iii,7 (when three unbranched rays present, first very short) [ii,7]; pectoral-fin rays 13 to 15 [15]; pelvic-fin rays i,8 [i,8].

Total vertebrae 30 (5), 31 (18), 32 (5).

COLOR IN ALCOHOL.—All examined specimens lacking guanine on scales, overall ground coloration tan. Upper lip, snout, and dorsal portions of head with field of small dark chromatophores. Scattered larger dark chromatophores on dorsal half of opercle, and over infraorbital series posterior and posteroventral to orbit. Lateral, dorsolateral, and dorsal surfaces of body with field of small dark chromatophores; overall intensity of field more pronounced dorsally. Pigmentation on those portions of body form irregular reticulate pattern. Deep-lying dusky stripe extending along midlateral surface of body from below dorsal fin to hypural joint in specimens under 40 mm SL; stripe extending forward to supracleithrum in two larger specimens examined (47.9–57.0 mm SL); stripe most obvious posteriorly. Deep-lying stripe becoming notably wider on posterior portion of caudal peduncle. Wider portion of deep-lying stripe overlain by roughly triangular patch of more superficially located dark chromatophores; patch of superficial chromatophores extending posteriorly onto basal portions of middle rays of caudal fin; posterior portion of superficial patch of chromatophores distinctly darker in some individuals, giving appearance of vertical bar on basal portion of caudal fin. Dorsal, adipose, and caudal fins somewhat dusky, with scattered small, dark chromatophores. Anal, pectoral, and pelvic fins hyaline.

DISTRIBUTION.—Known only from the type locality, the Río Aro of the Río Orinoco basin (Figure 80, locality 1).

ETYMOLOGY.—The species name, meniscaprorus, from the Greek meniskos, crescent, and prora, prow, refers to the rounded anterior portion of the head in this species.

ECOLOGY.—The type locality is a stream in gallery forest with muddy water with the bottom consisting of sand, gravel, boulder, and detritus.

TYPE MATERIAL EXAMINED.—31 specimens (31, 29.4–57.0).

HOLOTYPE.—VENEZUELA. Bolívar: Río Aro, about 3 km downstream from bridge at Rt. 19, about 85 km from Ciudad Bolívar (approx. 8°0′N, 64°15′W), collected by J. Baskin et al., 4 Nov 1979, MBUCV V-20333, 1 (57.0).

PARATYPES.—VENEZUELA. Bolívar: Río Aro, about 3 km downstream from bridge at Rt. 19, about 85 km from Ciudad Bolívar (approx. 8°0′N, 64°15′W); 30 specimens collected with holotype: MBUCV V-20334, 15 (29.4–37.8); USNM 235484, 15 (30.0–47.9; 2 specimens cleared and counterstained for cartilage and bone).

NON-TYPE MATERIAL EXAMINED.—151 specimens (11, 22.1–32.9).

VENEZUELA. Bolívar: Río Aro, about 3 km downstream from bridge at Rt. 19, about 85 km from Ciudad Bolívar (approx. 8°0′N, 64°15′W) (collected with holotype), USNM 309288, 75 (10, 22.1–29.8); MBUCV V-20335, 75; USNM 235461, 1 (32.9).