Male worms of Ancylostoma braziliense, A. ceylanicum, A. kusimaense, A. malayanum, A. duodenale, A. caninum, A. tubaeforme, Agriostomum vryburgi and Cyclodontostomum purvisi have the external appendages beside the anogenital aperture. These anogenital structures are morphologically similar and are assumed to be homologous among the species with three pairs of teeth or more. In hookworms with two pairs of teeth, the anogenital structures are complex. Anogenital features can be used as a taxonomic character in separating the species.