During a survey of plant-parasitic nematodes associated with walnut trees in Hamadan province, west Iran, several species of Longidoridae and infraorder Tylenchomorpha, including Paratylenchus paraperaticus sp. n., were identified. Paratylenchus paraperaticus sp. n. is characterised by its small size (255-385 μm), young female vermiform and ventrally curved, older female obese, swollen in prevulvar region and J- or W-shaped; truncate conical head with distinct and laterally protruding submedian lobes; long and flexible stylet (75.0-96.5 μm); body cuticle with fine and smooth annuli in young females, but in older females ornamented with minute reflective tubercles or irregularities that are confined mostly to the neck region; lateral field with four lines; presence of lateral vulval flaps; rounded to ovoid spermatheca filled with small, rounded sperm; and conical and ventrally curved tail with pointed to finely rounded terminus. [ABSTRACT FROM AUTHOR]