Parapedocotylinae, a new subfamily, is proposed to accommodate the gen. n. et sp. n. Parapedocotyle prolatili (Monogenea: Diclidophoridae), a gill parasite of the Pacific sandperch, Prolatilus jugularis (Valenciennes) (Pinguipedidae) from northern Chile (30 degrees 56'S; 71 degrees 20'W). Among the Diclidophoridae Cerfontaine, 1895, the species of the Pedocotylinae Yamaguti, 1963 are unique by bearing the first pair of clamps (most posteriorly) in a haptoral projection. Pedocotyle MacCallum, 1913, the only genus in the Pedocotylinae, is characterised by the first pair of clamps non-pedunculate, modified and non-functional, without accessory suckers, and clamps of pairs 2-4 being pedunculate and functional. In contrast, the first pair of clamps in Parapedocotyle is well developed and functional at the terminal end of a long haptoral appendix and having clamp pairs 2-4 pedunculated, modified and apparently not functional. Seminal receptacle is preovarian in Parapedocotyle in opposition to its postovarian position in Pedocotyle. These differences justified the erection of the new subfamily Parapedocotylinae. The new subfamily is also supported by genetic analyses (18S rDNA, 28S rDNA and cox1 sequences) demonstrating that the Pedocotylinae and Parapedocotylinae belong to different clades in the Diclidophoridae.