title: A new species of Moenkhausia Eigenmann, 1903 (Characiformes, Characidae) from the rio Amazonas basin, Brazil.
abstract: Moenkhausia abyss is herein described from the rio Amazonas basin lowlands. The new species can be distinguished from the congeners by presenting the combination of the following characters: a dark blotch located on the upper caudal-fin lobe and the lower lobe hyaline, 25-29 branched anal-fin rays, humeral spot rectangular, vertically oriented, extending horizontally through two or two and a half scales and located over the third to the fifth lateral line scales, five longitudinal scale rows above the lateral line, predorsal scales arranged in a single not interrupted median row and 30-34 perforated lateral line scales. Brief comments on Moenkhausia megalops are provided.
authors.affiliation: Universidade Santa Cecília, Rua Oswaldo Cruz 277, Boqueirão, CEP 11045-907, Santos, SP, Brazil.; Email: gu_darlim@hotmail.com.
authors.forename: Gustavo D
authors.initials: GD
authors.lastname: Oliveira
authors.affiliation: Museu de Zoologia da Universidade de São Paulo, Avenida Nazaré 481, Ipiranga, CEP 04203-001, São Paulo, SP, Brazil; Email: manumfm@yahoo.com.br.
authors.forename: Manoela M F
authors.initials: MM
authors.lastname: Marinho
mesh_terms: D063147:Animal Distribution; D000825:Animal Structures / Q000033:anatomy & histology / Q000254:growth & development; D000818:Animals; D049628:Body Size; D001938:Brazil; D060126:Characidae / Q000033:anatomy & histology / Q000145:classification* / Q000254:growth & development; D017753:Ecosystem; D005260:Female; D008297:Male; D009929:Organ Size