Leporinus santosi

description

Description. Morphometric data in Table 1. Middle-sized, when compared to congeners; largest examined specimen 155.0 mm SL (MZUSP 32307). Head and body moderately compressed and relatively deep. Dorsal profile convex from snout tip to dorsal-fin origin, somewhat straight along dorsal-fin base, straight and descending slightly from dorsal-fin end to adipose-fin origin, and usually concave from adipose-fin origin to anteriormost procurrent ray of caudal fin. Ventral profile convex from lower jaw to pelvic-fin origin, straight from latter point to anal-fin origin, convex along anal-fin base, and concave from anal-fin end to anteriormost procurrent ray of caudal fin. Greatest body depth at or slightly anterior to dorsal-fin origin. Mouth terminal, its cleft longitudinally aligned with middle of orbit in specimens up to approximately 60 mm SL, or to ventral margin of eye in larger specimens. Snout rounded, anteriorly blunt. Premaxilla with four (24) incisiform teeth gradually decreasing in size from symphyseal tooth. Dentary with four (24) incisiform teeth also gradually decreasing in size posterolaterally (Fig. 2). Scales cycloid, with 5 (1) or 7 (2) radii. Lateral line complete with 3

A new species of Leporinus Agassiz, 1829 (Characiformes: Anostomidae) from the rio Tocantins, Brazil

diagnosis

Diagnosis. Leporinus santosi is distinguished from all congeners, except for L. gomesi, L. granti, and L. nijsseni, for having three prominent dark midlateral blotches, smaller blotches formed by dermal pigment, five of which form an interrupted “ X ” between head and first midlateral blotch, small dark spots formed by epidermal pigment, terminal mouth with four teeth on premaxilla and four on dentary, and relatively few scales on lateral line (less than 36). Leporinus santosi is further distinguished from all congeners, except L. gomesi, by having a conspicuous dark spots on the center of scales on anterolateral portion of the body (Figs. 1 a, b and 5 a). Leporinus santosi is distinguished from L. gomesi by having 16 (vs. 12) scale rows around the caudal peduncle, and the second midlateral dark blotch rounded and not extended posteriorly to the vertical through the posterior margin of the adipose fin (vs. second midlateral dark blotch elongate, extended posteriorly to the vertical through the posterior margin of the adipose fin).

A new species of Leporinus Agassiz, 1829 (Characiformes: Anostomidae) from the rio Tocantins, Brazil

distribution

Geographic distribution. Leporinus santosi is known from a tributary of the rio Tocantins, at the stretch now inundated by the Tucuruí reservoir, and a tributary of the rio Itacaiúnas, a large tributary of the lower rio Tocantins (Fig. 3).

A new species of Leporinus Agassiz, 1829 (Characiformes: Anostomidae) from the rio Tocantins, Brazil

etymology

Etymology. Named in honor of Geraldo Mendes dos Santos, a researcher from INPA, for his important contributions to our knowledge of the fish fauna of the lower rio Tocantins, through his studies on the species of Anostomidae (Santos & Jégu, 1989), and on the impacts of the Tucuruí dam (Santos et al., 1984; Santos et al., 2004). An noun.

A new species of Leporinus Agassiz, 1829 (Characiformes: Anostomidae) from the rio Tocantins, Brazil