Description of Oswaldocruzia peruensis n. sp. parasite of Stenocercus roseiventris from Peru. O. peruensis belongs to the group of Oswaldocruzia spp. characterized by : (1) three spicular branches (blade, fork and shoe) with the fork subdivided at its distal extremity and the blade subdivided into many processes ; and (2) by a type II bursal pattern of rays 6, 8 and dorsal. The only closely related species, O. vaucheri Ben Slimane & Durette-Desset, 1993, a parasite of leptodactylids in Ecuador, differs by the presence of cuticular crests which undulate and by the shape of the cervical alae.