title: Two new species of Hyphessobrycon (Characiformes: Characidae) from the headwaters of the Tapajós and Xingu River basins, Pará, Brazil.
abstract: Two new species of Hyphessobrycon are described from the headwaters of the Tapajós and Xingu River basins, Pará, Brazil. Both new species can be distinguished from congeners by the presence of a vertically elongate humeral blotch, a conspicuous round to vertically oblong caudal-peduncle blotch not extending onto the distal portions of the middle caudal-fin rays, a conspicuous blotch on the central portion of the third infraorbital immediately ventral to the eye, the lack of a conspicuous longitudinal stripe and the lack of sexual dimorphism in the extension of the caudal-peduncle blotch. Hyphessobrycon delimai n. sp. can be distinguished from Hyphessobrycon krenakore n. sp. by the extent of the caudal-peduncle blotch which extends across most of the caudal-peduncle depth (v. restricted to the middle portion of the caudal peduncle), the presence of dark chromatophores uniformly scattered along the length of the interradial membranes of the dorsal, anal and caudal fins (v. concentrated on the distal one-half or one-fourth of the interradial membranes) and the absence of small bony processes on the pelvic and anal fins of mature males (v. small bony processes present).
authors.affiliation: Museu de Zoologia da Universidade de São Paulo, Caixa Postal 42494, 04218-970, São Paulo, SP, Brazil.
authors.forename: T F
authors.initials: TF
authors.lastname: Teixeira
authors.affiliation: Museu Paraense Emílio Goeldi, Avenida Perimetral, 1901, caixa postal 399, 66077-530, Belém, Pará, Brazil.
authors.forename: A L
authors.initials: AL
authors.lastname: Netto-Ferreira
authors.affiliation: Departamento de Biologia Animal e Vegetal, Universidade Estadual de Londrina, Caixa Postal 10011, 86057-970, Londrina, PR, Brazil.
authors.forename: J L O
authors.initials: JL
authors.lastname: Birindelli
authors.affiliation: Faculdade de Ciências Biológicas, Universidade Federal do Pará, campus Universitário de Altamira, 68372-040, Altamira, PA, Brazil.
authors.forename: L M
authors.initials: LM
authors.lastname: Sousa
mesh_terms: D058500:Animal Fins / Q000033:anatomy & histology; D000818:Animals; D001938:Brazil; D060126:Characidae / Q000033:anatomy & histology* / Q000145:classification*; D005260:Female; D008297:Male; D045483:Rivers; D014070:Tooth / Q000033:anatomy & histology
keywords: Neotropical; fresh water; sexual dimorphism; taxonomy