Scomberomorocotyle munroi ng, n sp (Scomberomorocotylinae n subf), a thoracocotylid monogenean from Scomberomorus munroi (Scombridae) off Australia and Papua New Guinea

Scomberomorocotyle munroi n. g., n. sp. is described from the gills of Scomberomorus munroi, a Spanish mackerel from the coasts of northern Australia and southern Papua New Guinea. The genus belongs to the suborder Gastrocotylinea because a pair of basal accessory sclerites is present in the clamps. However, the worm does not belong to any of the eight gastrocotylinean families as they are currently recognised. The worm appears to be a member of the Thoracocotylidae, in that the male copulatory organ has relatively weakly developed spines, and that the haptor is one-sided with two rows of clamps. However, the worm differs from all thoracocotylids in that the clamps lack the characteristic lateral rib-like thickenings. To accommodate the new genus and species, the diagnosis of the Thoracocotylidae Price is amended to include worms lacking ribs in their clamps, and a new subfamily, the Scomberomorocotylinae n. subfam., is erected; a key to the four subfamilies which we recognise as valid is provided.