A new species of Rhinonastes (Monogenoidea, Dactylogyridae), nasal parasite of Prochilodus argenteus (Actinopterygii, Characiformes) from Brazil.

A new species of Rhinonastes, hitherto monotypic, is described and illustrated from the nasal cavity of 'curimat', Prochilodus argenteus from São Francisco River, Brazil. Rhinonastes curimatae n. sp. presents a male copulatory organ with more than five rings while the type species of the genus is characterized by male copulatory organ with less than two rings. This is the first record of a nasal parasite in P. argenteus.