Brycon stolzmanni

description

Description. Morphometric data are presented in Table 1. Relatively small-sized species, largest examined specimen 214.0 mm SL. Body moderately high. Largest body height at dorsal-fin level. Dorsal body profile slightly convex from upper lip margin to vertical through anterior naris, slightly concave to slightly convex from latter point to basis of supraoccipital process, and moderately convex from latter point to dorsal-fin origin, straight along dorsal-fin basis, straight to slightly convex from dorsal-fin terminus to adipose-fin origin. Dorsal profile of caudal peduncle slightly concave. Ventral profile slightly convex from lower lip to pelvic-fin insertion, slightly convex to straight from this point to anal-fin origin and approximately straight along anal-fin base. Ventral profile of caudal peduncle slightly concave. Head profile rounded to slightly acute anteriorly, mouth terminal. Maxillary extending posteriorly to vertical slightly anterior to middle of pupil. Adipose eyelid well developed. Premaxillary teeth in three rows; teeth of third row largest. Five (7), 6 (16), 7 (10) or 8 (1) tricuspidate teeth in outer series. Two (4), 3 (25), or 4 (7) tri- to pentacuspidate teeth

A revision of the cis-andean species of the genus Brycon Müller & Troschel (Characiformes: Characidae)

diagnosis

Diagnosis. Brycon stolzmanni can be distinguished from all remaining cis-andean Brycon species, except B. coxeyi, by possessing a distinct patch of dark pigmentation on the opercle (vs. patch of dark pigmentation on the opercle absent in the remaining cis-andean Brycon species) and infraorbital series not closed, with the orbital margin partially delimited by the frontal bone (vs. infraorbital series closed, frontal excluded from the orbital series by the contact between the supraorbital and the sixth infraorbital bone). Brycon stolzmanni can be distinguished from B. coxeyi by possessing the dark patch of pigmentation on the opercle diffuse and covering the upper half of the bone (vs. dark patch of pigmentation on opercle very conspicuous and typically lying at its center).

A revision of the cis-andean species of the genus Brycon Müller & Troschel (Characiformes: Characidae)

discussion

Remarks. Steindachner (1879 a: 152) succinctly described Brycon stolzmanni, a complete description and a illustration of the species appearing a little later (1879 b: 22). The species was described based on two specimens collected at Chota, upper Río Marañon basin, Departamento Cajamarca, Peru. The two syntypes (NMW 62731) were examined, the largest of which is herein designated as the lectotype of the species. There have been almost no subsequent published information on the species, and in fact, Pearson (1937) report of the species for several localities in the upper Río Marañon basin in Peru was the sole paper to add original information on the species up to now.

A revision of the cis-andean species of the genus Brycon Müller & Troschel (Characiformes: Characidae)

distribution

Distribution. Brycon stolzmanni is known from the upper Río Marañon and its tributaries at the Departamentos Cajamarca, Lambayeque, and Amazonas, Peru (Fig. 10). Fowler (1943: 4) and Howes (1982: 44) incorrectly assigned the species for the Pacific slope of the Andean cordillera. Ecological notes. Brycon stolzmanni is recorded from Andean rivers in altitudes ranging at least from 870 – 1087 meters high. The type locality, Chota, is situated in the headwaters of the Río Chamaya, a tributary of the upper Río Marañon, at a considerably higher altitude (2400 meters high). However, its is uncertain whether the type specimens were collected at Chota itself or in a neighboring river valley, and consequently we did not included this record in the altitudinal range cited above. The Río Marañon and its tributaries at the area of occurrence of Brycon stolzmanni are swift-flowing, white-water rivers possessing coarse gravel and rocky substrates running over braided channels, deeply entrenched in valleys crossing the mountains.

A revision of the cis-andean species of the genus Brycon Müller & Troschel (Characiformes: Characidae)