EN
Oxyascaris mcdiarmidi sp. nov. (Nematoda, Cosmocercidae) from the small intestine of Duellmanohyla uranochroa from Costa Rica is described. Oxyascaris mcdiarmidi sp. nov. represents the 4th species assigned to the genus and is distinguished from congeners by the distribution pattern of the caudal papillae of the male, spicule length and vulvar position.