Cynopotamus xinguano

description

Description. Morphometric data of holotype and additional specimens summarized in Table 1. Meristic and morphometric data based on all lots examined since no statistical differences were found among populations studied from different localities. Body comparatively large (SL = 84 – 180 mm SL) and anteriorly deep. Dorsal body profile concave at nape, rising sharply in supraoccipital region, strongly convex from this point to dorsal-fin origin, nearly straight along dorsal-fin base, and very slightly convex from dorsal-fin termination to caudal peduncle. Ventral body profile continuously convex from tip of lower jaw to anal-fin origin, straight or nearly so and dorsally inclined along anal-fin base, slightly concave from anal-fin termination to origin of procurrent caudal-fin rays. Snout conical, shorter than orbital diameter. Lower jaw included in upper jaw when mouth is entirely closed. Maxilla extending slightly beyond vertical crossing posterior border of orbit. Dorsal-fin rays ii, 9. Posteriormost ray branched. Adipose fin present. Anal-fin unbranched rays iv – v (iv), usually iv, branched rays 39 – 45 (43), 41.4, posteriormost ray split to its base and counted as 1. Weakly devel

A new species of Cynopotamus Valenciennes, 1849 (Characiformes, Characidae) with a key to the species of the genus

diagnosis

Diagnosis. Cynopotamus xinguano belongs to the group of species characterized by ii, 9 dorsal-fin rays [versus ii, 10 in C. argenteus (Valenciennes)] and 91 – 125 perforated lateral-line scales (versus 85 – 90 in C. juruenae Menezes) (Menezes, 1976, 1987). It is most similar to C. essequibensis, in number of horizontal rows of scales below lateral line ranging from 17 – 21, but differs by having more developed gill-rakers on first branchial arch (10 – 11 versus 8 – 9 in C. essequibensis), and the black humeral blotch wider (compare Tables 1 and 2). In C. xinguano the first pleural rib and the opening anterior to it are entirely covered by fibers of the obliquus superioris muscle, but the second pleural rib and the obliquus inferioris muscle are visible. In C. essequibensis the first pleural rib and opening anterior to it are visible and the second pleural rib and the obliquus inferioris muscle are totally covered by fibers of the obliquus superioris muscle (compare Figures 2 A and 2 B).

A new species of Cynopotamus Valenciennes, 1849 (Characiformes, Characidae) with a key to the species of the genus

distribution

Distribution. Cynopotamus xinguano is so far known only from tributaries of the rio Xingu basin (Figure 3).

A new species of Cynopotamus Valenciennes, 1849 (Characiformes, Characidae) with a key to the species of the genus

etymology

Etymology. This species is named after the Xinguano an Amerindian tribe living in Parque Indígena do Xingu, a national park in the rio Xingu basin. A noun in apposition.

A new species of Cynopotamus Valenciennes, 1849 (Characiformes, Characidae) with a key to the species of the genus