Ancylocoelium typicum Nicoll, 1912 (Digenea: Monorchiidae), a poorly known parasite of Trachurus spp. (Teleostei: Carangidae) from the western Mediterranean and north-eastern Atlantic, and observations on its taxonomic position.

The monorchiid digenean Ancylocoelium typicum Nicoll, 1912, a parasite of the horse mackerel Trachurus trachurus (Carangidae), was essentially known from two descriptions based, respectively, on one and three specimens. It is redescribed and figured in detail based on numerous specimens from the rectum of three Trachurus spp. off Corsica in the western Mediterranean. It is compared with the type-species of the genus Lasiotocus Looss in Odhner, 1911, L. mulli (Stossich, 1883), for which new illustrations are provided, and, although they are easily distinguishable, they are not considered distinct at the generic level. The new combination Lasiotocus typicus is formed. It is also compared with the type-species of Chrisomon Manter & Pritchard, 1961, C. tropicus (Manter, 1940), for which new illustrations of the type-specimen are provided, and is found to be distinguishable, but not at the generic level. Chrisomon is, therefore, synonymised with Lasiotocus and the new combination L. tropicus is formed. It is not clear whether all nominal species of Chrisomon are also congeneric with Lasiotocus species.