A new species of Anacanthoroides and redescription of Apedunculata discoidea (Monogenoidea) parasitizing Prochilodus argenteus (Actinopterygii) from the São Francisco River, Brazil.

Anacanthoroides sanctifrancisci n. sp. from the gills of 'curimatã-pacú', Prochilodus argenteus from the São Francisco River, Brazil, is described and illustrated. Anacanthoroides, monotypic, is represented by Anacanthoroides mizellei. The new species can be distinguished from A. mizellei by the presence of a pair of muscular pseudosuckers in the anterior region of the body, an accessory piece not articulated to the male copulatory organ and the number of rings in the male copulaty complex. Apedunculata discoidea is redescribed and recorded in the gills of P. argenteus. The generic diagnosis of Apedunculata is amended. Both genera are recorded for the first time in the São Francisco River basin.