title: Redescription of Hysteronotus megalostomus (Characiformes: Characidae: Stevardiinae), a poorly known characid from tributaries of the Rio São Fancisco, Brazil with comments on the conservation of the species.
abstract: Originally described from the upper Rio das Velhas, a tributary of the Rio São Francisco, state of Minas Gerais, Brazil, Hysteronotus megalostomus was recently collected in many tributaries of the Rio São Francisco north of the type locality. The specimens of the population samples collected outside the type locality share the morphological features present in the type material except for the presence of an adipose fin found only in two specimens within the more recently collected material. Presence or absence of the adipose fin has been extensively used by fish taxonomists to characterize different species and even genera, but in H. megalostomus the character is not consistent, indicating its use alone is not diagnostic. The species is redescribed and its phylogenetic relationships and conservation status are briefly discussed.
authors.affiliation: Museu de Zoologia, Universidade de São Paulo, P. O. Box 42494, CEP 04218-970, São Paulo, SP, Brazil.
authors.forename: N A
authors.initials: NA
authors.lastname: Menezes
authors.affiliation: Smithsonian Institution, Division of Fishes, P. O. Box 37012, Washington, D.C., U.S.A.
authors.forename: S H
authors.initials: SH
authors.lastname: Weitzman
authors.affiliation: Museu de Zoologia, Universidade de São Paulo, P. O. Box 42494, CEP 04218-970, São Paulo, SP, Brazil.
authors.forename: T F
authors.initials: TF
authors.lastname: Teixeira
mesh_terms: D000818:Animals; D001938:Brazil; D060126:Characidae / Q000033:anatomy & histology* / Q000145:classification / Q000502:physiology; D003247:Conservation of Natural Resources; D005260:Female; D008297:Male; D010802:Phylogeny; D012727:Sex Characteristics; D013045:Species Specificity
keywords: conservation; fresh water; neotropical; sexual dimorphism; systematics