Abstract
Three species of mononchids belonging to the Prionchulus Cobb, 1916 genus, one new and two previously known species collected from natural ecosystem of Khorramabad county, Lorestan province, south west of Iran, are described. Prionchulus girchi sp. nov. is morphologically characterized by its 2.1 - 2.2 mm body length, numerous cuticular pores, slightly offset lip region, prominent labial and cephalic papillae, cephalic papillae larger than labial ones, barrel-shaped and spacious (40 - 43 × 22.5 - 24 μm) buccal cavity, weakly rounded tail tip and weakly expressed tail tip´s hyaline. In this study, P. fagi and P. muscorum were also collected and some additional data of these two species are also given.