A new species of Haematoloechus Looss, 1899 (Digenea: Plagiorchioidea: Haematoloechidae), a parasite of Rana psilonota Webb and R. zweifeli Hillis, Frost & Webb (Anura: Ranidae) in Mexico.

During an inventory of the helminths of amphibians in Mexico, specimens of an undescribed species of Haematoloechus Looss, 1899 (Digenea: Haematoloechidae) were collected from the lungs of frogs of the "tarahumarae" group in western México. Haematoloechus longicollum n. sp. differs from other known species of Haematoloechus by the combination of the following characters: body elongate and slender in the preovarian region and broad and blunt in the postovarian region, ovary separated from the ventral sucker more than twice the ovary length, oral sucker to pharynx length ratio 1:0.56, oral sucker to ventral sucker length ratio 1:0.80, presence of extracaecal uterine loops, absence of longitudinal extracaecal uterine loops, ovary and testes oval.