Hookfin Tetra

description

Description. Morphometric data for Hyphessobrycon otrynus are summarized in Table 1. Body fusiform. Greatest body depth at dorsal-fin origin. Dorsal profile of head straight or slightly convex. Dorsal profile of body slightly convex from posterior tip of supraoccipital spine to dorsal-fin origin, straight or slightly convex and posteroventrally slanted along dorsal-fin base, straight or slightly convex from end of dorsal-fin base to end of adipose-fin, and slightly concave along caudal peduncle. Ventral body profile convex from anterior tip of lower jaw to caudal-peduncle origin, slightly concave along caudal peduncle. Pelvic region transversally flattened, more so proximal to pelvic-fin insertion, becoming somewhat obtuse toward anal-fin origin. Mouth terminal. Jaws equal or lower jaw slightly longer than upper jaw. Most posterior margin of maxilla trespassing vertical through anterior margin of orbit. Premaxillary teeth in two rows; outer tooth row with 3 (4), 4 * (6) conical to tricuspid teeth, midcentral cusps longer than others; inner tooth row with 5 tri to pentacuspid teeth in all specimens, midcentral cusps longer than others. Maxillary with 0 (2) and 1 * (8) conical tooth.

A new species of Hyphessobrycon (Characiformes: Characidae) from río Portuguesa, río Orinoco basin, Venezuela

diagnosis

Diagnosis. This species is distinguished from all other known congeners, except for H. diancistrus, by the presence of two very large bony hooks (in adult males) curving dorsally on each side of anal fin, and caudalfin rays black at distal third of their length (distal tips of caudal-fin rays hyaline). Hyphessobrycon otrynus is promptly distinguished from H. diancistrus by possessing iv, 19 – 21 anal fin rays, versus iv, 14 anal-fin rays in the latter. Adult males of H. otrynus are also distinguished from H. diancistrus by presenting very small analfin hooks, lacking from the latter species. Moreover, in H. otrynus, the very large bony hooks are located on the fourth or fifth segments of the last unbranched anal-fin ray and on the fifth segment of the first branched anal-fin ray, whereas in H. diancistrus the bony hooks are located on the first and third segments of the last unbranched and first branched anal-fin rays. Among small characins, Hyphessobrycon otrynus is most similar to Moenkhausia bonita and Hemigrammus marginatus, from which it differs in having a naked caudal-fin (vs. a scaled caudal-fin), by presenting two large hooks on anal-fin of adult males (not observable in l

A new species of Hyphessobrycon (Characiformes: Characidae) from río Portuguesa, río Orinoco basin, Venezuela

discussion

Comments. According to Ellis (in Eigenmann, 1918), Hyphessobrycon is distinguished from Hemigrammus only by presenting a naked caudal fin in opposition of the scaled caudal fin in the last genus. However, Weitzman (1977) affirmed that these genera cannot be distinguished either phylogentically or typologically as separate taxa because, as Böhlke (1955) pointed out, there are species which are intermediate in their caudalfin squamation. Even so, this author recognized his new species as belonging to Hyphessobrycon rather than Hemigrammus, employing a practical, typological procedure (amount of caudal-fin squamation), and based on the traditional definitions of these genera provided by Ellis (in Eigenmann, 1918). Hyphessobrycon otrynus shares with H. diancistrus the identical color pattern and the presence of two large hooks on each side of the caudal fin, which are indicative of a close relationship. Thus, we follow Weitzman (1977) in recognizing this new species in the genus Hyphessobrycon, emphasizing the putatively close relationship between these species. Weitzman (1977) discussed that large anal-fin hooks are known in other species of Hyphessobrycon and Hemigrammus and cited He

A new species of Hyphessobrycon (Characiformes: Characidae) from río Portuguesa, río Orinoco basin, Venezuela

distribution

Distribution. Known only from tributaries of the río Portuguesa, río Orinoco drainage, Venezuela (fig. 5).

A new species of Hyphessobrycon (Characiformes: Characidae) from río Portuguesa, río Orinoco basin, Venezuela