Lamellodiscus crampus sp. nov. (Monogenea, Diplectanidae) is described from the gills of Dentex maroccanus (Valenciennes) collected from the Gulf of Gabès (Tunisia) in the oriental part of Mediterranean Sea. The new species belongs to the “ignoratus” group (sensu Oliver 1987) characterized by a lamellodisc with complete lamellae and a “lyre” shaped male copulatory organ, and the “ignoratus” sensu stricto subgroup, characterized by a haptor with simple lateral dorsal bars, as proposed by Amine and Euzet (2005). Lamellodiscus crampus can be easily distinguished from all the congeneric species of the subgroup “ignoratus” by the presence, in the “lyre” male copulatory organ, of five spines in the distal portion on the axial side of the paired piece.