Comprehensive Description
(
anglais
)
fourni par Smithsonian Contributions to Zoology
Cyphocharax vexillapinnus
DIAGNOSIS.—The combination of 28 to 31 scales in a longitudinal series along the body, the black spot on the central portion of the anterior rays of the dorsal fin, and the limitation of the pores of the laterosensory canal system of the body to the 5 to 8 anterior scales of the midlateral scale series distinguishes Cyphocharax vexillapinnus from all congeners, and indeed all curimatids.
The only other Cyphocharax species with a distinct patch of dark pigmentation on the dorsal fin is C. notatus, in which the distal rather than central portions of the fin are intensely pigmented. The two species also differ in the degree of development of pores along the lateral-line scale series (pores developed only on anterior 5 to 8 scales in vexillapinnus versus along entire series in notatus), relative body depth (0.38–0.47 of SL versus 0.31–0.37 respectively), and relative depth of caudal peduncle (0.14–0.16 of SL versus 0.11–0.13).
DESCRIPTION.—Body moderately deep, more so in larger individuals (compare Figures 20–22); compressed laterally. Dorsal profile of head convex from tip of snout to vertical line through posterior nostril, straight or slightly convex from that line to tip of supraoccipital spine. Dorsal profile of body smoothly curved from tip of supraoccipital spine to origin of dorsal fin; straight and posteroventrally slanted at base of dorsal fin, straight from base of last dorsal-fin ray to caudal peduncle. Dorsal surface of body with indistinct 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 somewhat flattened, with regular median series of scales that are not enlarged relative to those of adjoining portions of body. Median scale series flanked on each side by series of scales matching obtuse lateral angles of prepelvic region of body. Obtuse median keel posterior to origin of pelvic fin. Secondary obtuse keel on each side of postpelvic portion of body about two scales dorsal of ventral midline.
Greatest body depth at origin of dorsal fin, depth 0.38–0.47 [0.46], specimens larger than 20 mm SL with distinctly deeper bodies; snout tip to origin of dorsal fin 0.51–0.55 [0.53]; snout tip to origin of anal fin 0.86–0.92 [0.90]; snout tip to origin of pelvic fin 0.54–0.60 [0.58]; snout tip to anus 0.82–0.88 [0.86]; origin of dorsal fin to hypural joint 0.53–0.59 [0.58]. Dorsal fin pointed in profile anterodistally; last unbranched and first branched rays about three times length of ultimate ray. Pectoral fin pointed in profile distally; length of pectoral fin 0.19–0.23 [0.20], extends about two-thirds distance to vertical line through origin of pelvic fin. Pelvic fin pointed in profile distally, length of pelvic fin 0.25–0.30 [0.27], tip of fin falling short of origin of anal fin. Caudal fin forked. Adipose fin well developed. Anal fin emarginate, anteriormost branched rays about two and one-half times length of ultimate ray. Least depth of caudal peduncle 0.14–0.16 (0.16 rare) [0.15].
Head pointed, head length 0.29–0.35 [0.29]; upper jaw somewhat longer than lower, mouth subterminal; snout length 0.24–0.30 [0.28]; nostrils of each side very close, anterior circular, posterior crescent-shaped with aperture closed by thin flap of skin separating nares; orbital diameter 0.33–0.36 [0.34]; adipose eyelid weakly developed, with broad opening over eye; length of postorbital portion of head 0.40–0.45 [0.43]; gape width 0.26–0.31 [0.27]; interorbital width 0.41–0.45 [0.43].
Scales in longitudinal midlateral series from supracleithrum to hypural joint 28 to 31 (most often 29 or 30) [29]; anterior 5 to 8 scales of midlateral scale series pored [5], canals in pored scales straight; 2 or 3 scales in horizontal series continuous with that including pored portion of lateral line extend beyond hypural joint onto caudal-fin base; 512 to 612 scales in transverse series from origin of dorsal fin to horizontal scale series including pored scales [612]; 412 scales in transverse series below horizontal scale series including pored scales to origin of anal fin; 12 to 1312 [13] scales in transverse series from origin of dorsal fin to midventral line.
Dorsal-fin rays ii,9 or iii,9 (iii,9 much less common, when three unbranched fin rays present, first very short) [iii,9]; anal-fin rays ii,7 or 8 or iii,7 (when three unbranched rays present, first very short) [ii,8]; pectoral-fin rays 13 or 14 [14]; pelvic-fin rays i,8 [i,8].
Total vertebrae 30 (4), 31 (25), 32 (2).
COLOR IN ALCOHOL.—Overall coloration of specimens retaining guanine on scales silvery. Ground coloration of specimens lacking guanine on scales yellowish-tan, darker on dorsal portions of head and body. Head without pronounced pigmentation pattern. Scale margins on dorsal and dorsolateral portions of body with margins outlined by series of small chromatophores; dark chromatophore fields along scale margins more pronounced dorsally. Dorsal fin with prominent rotund patch of dark pigmentation extending from anterior margin of fin across unbranched and anterior branched rays. Dark pigmentation located on basal half of fins, but with ventral margin of pigmentation patch distinctly separated ventrally from dorsal surface of body by a horizontally elongate unpigmented region along ventral margin of fin (see Figures 20–22). Dark pigmentation on dorsal fin particularly intense and distinct in smaller specimens. This pigmentation not as dark or discrete in larger individuals. Remainder of dorsal fin and caudal fin with fin rays outlined by series of small dark chromatophores. Other median fins and paired fins hyaline.
AUTAPOMORPHIES OF Cyphocharax vexillapinnus.—The form of the patch of dark pigmentation on the dorsal fin in C. vexillapinnus is unique to that species in the Curimatidae. Dark spots of pigmentation on the dorsal fin are found in some other curimatids, most notably Cyphocharax notatus and various species of Steindachnerina. The pigmentation in those species differs, however, in the distribution of dark chromatophores on the fin. In C. vexillapinnus, contrary to C. notatus, the central rather than distal portions of the anterior rays of the dorsal fin are dark (compare Figures 20–22 and 23, 24). The dark spot of pigmentation in many species of Steindachnerina, in turn, occurs on the basal portions of the middle rays of the fin (see figures in Vari, 1991). The dark dorsal fin pigmentation in Cyphocharax vexillapinnus is consequently hypothesized to be an autapomorphy for the species.
As noted in the discussion of the infraorbital ossifications under “Phylogenetic Comments” there is a pronounced reduction in the development of the infraorbital series and the associated segments of the laterosensory canal in Cyphocharax vexillapinnus. The absence of the laterosensory canal segment in the first infraorbital and the pronounced reduction of the sixth infraorbital are derived features shared with some other members of the genus. Cyphocharax vexillapinnus is unique in the genus, however, in the pronounced reduction in the degree of development of the laterosensory canal segments in infraorbitals 2 through 4. Contrary to the situation in other curimatids, the laterosensory system associated with these elements is not enclosed in ossified canals, but rather, is at the most superficial to the lateral surface of the bone with a dorsal ridge of bone abutting the upper margin of the sensory canals.
DISTRIBUTION.—Middle and upper portions of Amazon basin (Figure 18).
ETYMOLOGY.—The specific name, vexillapinnus, from the Latin for flag and fin, is in reference to the prominent black spot on the dorsal fin.
TYPE MATERIAL EXAMINED.—22 specimens (22, 41.0–63.0).
HOLOTYPE.—PERU. Loreto: Rio Itaya, main river channel and mouth of caños entering river, 10 km upstream of Belén (Iquitos) (approx. 3°51′S, 073°12′W), collected by R.P. Vari, H. Ortega, and A. Gerberich, 20 Aug 1986, USNM 296394, 1 (63.0).
PARATYPES.—PERU. Loreto: Río Itaya, main river chanel and mouth of caños entering river, 10 km upstream of Belén (Iquitos) (approx. 3°51′S, 073°12′W), collected by R.P. Vari, H. Ortega, and A. Gerberich, 20 Aug 1986; 15 specimens collected with holotype: USNM 296361, 8 (41.6–62.2); MUSM 2721, 4 (47.1–58.6); MZUSP 41761, 3 (46.4–52.4). Río Corrientes drainage, Teniente López, pool in forest on right bank opposite military camp, S.O. Kullander et al., 30 Jul 1986, NRM 26569, 6 (41.0–48.3).
NON-TYPE MATERIAL EXAMINED.—438 specimens (19, 22.4–41.3).
BRAZIL. Amazonas: Lago Terra Preta, Januari, USNM 229174, 1 (41.3); USNM 229173, 4. Rio Solimões, Lago de Marchantaria, INPA uncat., 16 (10, 22.4–28.7). Lake near Manaus, USNM 296232, 3 (29.7–35.9). Rio Solimōes, Lago de Marchantaria, USNM 268045, 5 (23.3–27.8); USNM 313443, 8 (2 specimens cleared and counterstained for cartilage and bone). Mouth of Rio Negro, NMW 68815, 1.
PERU. Loreto: Río Itaya drainage, Quebrada Tocón Grande and nearby pools, at km 33 on carretera Iquitos-Nauta, NRM 26570, 2. Río Corrientes, Teniente López, NRM 26619, 396.
ECUADOR. Napo: Jatuncocha, BMNH 1970.4.3:92–93, 2.
- citation bibliographique
- Vari, Richard P. 1992. "Systematics of the Neotropical characiform genus Cyphocharax Fowler (Pisces:Ostariophysi)." Smithsonian Contributions to Zoology. 1-137. https://doi.org/10.5479/si.00810282.529
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