Empruthotrema stenophallus n. sp. (Monogenea: Monocotylidae) from the nasal tissue of Dasyatis kuhlii (Dasyatidae) from Sabah, Borneo, Malaysia.

Empruthotrema stenophallus n. sp. (Monogenea: Monocotylidae) is described from specimens from the nasal tissue of the blue-spotted maskray Dasyatis kuhlii (Muller and Henle, 1841) collected in shallow waters off Pulau Banggi and Pulau Mabul, Sabah, Borneo, Malaysia. This is the first monogenean species to be described from an elasmobranch collected from Sabah. E. stenophallus can be distinguished from the other 6 members of the genus by the morphology of the sclerotized male copulatory organ, which is narrow, short, and distally tapered. E. dasyatidis Whittington and Kearn, 1992, previously documented from the nasal tissue of several of elasmobranch species from Australia, is recorded from 8 host species distributed around Malaysian Borneo. These represent new host and locality records for this monocotylid. The difficulties in identifying species of Empruthotrema and the apparent lack of host specificity by some members of the genus are discussed.