A new species of Hemigrammus (Characiformes: Characidae) from western Amazon River basin, Colombia.

A new species of Hemigrammus is described from the Amazon Basin near Leticia, Departamento Amazonas, Colombia. In common with some congeners and some Hyphessobrycon spp., the new species colour pattern lacks a humeral blotch but has a caudal-peduncle blotch. It can be distinguished from congeners with a similar colour pattern by having: a relatively deep body (30.2%-39.0% LS ), 20-24 branched anal-fin rays, 6-8 perforated scales of the lateral line, anal-fin base without a conspicuous black stripe, 3-5 maxillary teeth, maxillary teeth with 1-3 cusps, a thin longitudinal midlateral line and a well-defined oval shaped caudal blotch, extending from caudal peduncle into the lower caudal-fin rays. Comparisons with congeners and with Hyphessobrycon species sharing the same general colour pattern are presented.