The present study describes a new species, Ligophorus uruguayense, parasitizing the gills of Mugil platanus Günther, 1880 from the coast of Uruguay. It differs from all other species of the genus mainly in the shape of the ventral bar, the thick process at the distal end of the inner root of ventral anchors, the J-shaped penis accessory piece and the vaginal tube showing transverse annulations at its distal end, the host species, and geographical distribution. This is the first description of a species of Ligophorus from a mullet in the South Atlantic Ocean.
Two types of metacercariae with 37 and 43 collar spines were obtained from Diplodon chilensis (Unionacea, Pelecypoda). They were fed to chicken and mice and mature adults with eggs were only obtained from the latter. These are described as a new species, Echinoparyphium megacirrus sp. n.