Three new species of Monocotyle (Monogenea: Monocotylidae) from the stingray, Himantura uarnak (Rajiformes: Dasyatidae) from the Great Barrier Reef: phylogenetic reconstruction, systematics and emended diagnoses.

Three new species of Monocotyle were found on the gills of the coachwhip stingray, Himantura uarnak (Rajiformes: Dasyatidae) collected at Heron Island, Great Barrier Reef, Australia (23 degrees 27' S, 151 degrees 55 'E). Monocotyle helicophallus new species, Monocotyle multiparous new species and Monocotyle spiremae new species all have a single testis and are distinguished from other described Monocotyle species by size of body and hamulus and number of coils of the sclerotized male copulatory organ (21-22, three to four and 29-42, respectively). Monocotyle helicophallus new species is characterized by several muscular genital papillae, one of which is traversed by the ejaculatory duct; M. spiremae new species is distinguished by a sclerotized accessory structure associated with the distal end of the male copulatory organ, a vaginal sclerite and a conspicuous spherical, ejaculatory bulb; M. multiparous new species is distinguished by a large number of retained, thin-shelled eggs, many of which contain a fully developed oncomiracidium. A phylogenetic analysis of the 14 described species of Monocotyle utilizing 13 characters (11 binary and two multistate) produced the most parsimonious cladogram involving 18 steps with a consistency index of 0.78, two homoplasies and four unresolved polychotomies. Emended diagnoses of the Monocotylinae and Monocotyle are provided.