Description of a new dagger nematode, n. sp. (Nematoda: Longidoridae) and additional data on the three known species of the genus from northwest of Iran.

n. sp. collected from the rhizosphere of common wheat ( L.) in Roodghat area, Sufiyan, East-Azarbaijan province, northwest of Iran, is described on the basis of the morphological, morphometric and molecular data. The new species belongs to morphospecies group 6 of the polytomous key prepared by Loof and Luc, 1990. n. sp. is characterized by having two almost equally developed female reproductive branches with spines in the tubular portion of the uterus, a body length of 3.67-4.25 mm, a flat lip region, rounded cephalic region, separated from body contour by a shallow depression, a spear 215-225 μm long, mid-body diameter of 60-79 μm, vulva (46-48%), a short tail (30-38 µm, c = 103-133, c' = 0.7-0.9), conoid, dorsally convex, ventrally directed with a small terminal peg and a distinct terminal blind canal, the presence of four juvenile stages and the absence of males. The polytomous identification codes of the new species are: A4, B3, C5a, D6, E5, F4, G3, H2, I3, J4, K2, L1. In addition to morphological and morphometric data, molecular analyses of the D2-D3 expansion regions of the 28S rDNA gene placed the new species as a sister species of (Group 5) with 65% Bayesian posterior probability and further separated this species from the other members in group 6. In this study, , and were also collected and additional data for the species were provided. n. sp. collected from the rhizosphere of common wheat ( L.) in Roodghat area, Sufiyan, East-Azarbaijan province, northwest of Iran, is described on the basis of the morphological, morphometric and molecular data. The new species belongs to morphospecies group 6 of the polytomous key prepared by Loof and Luc, 1990. n. sp. is characterized by having two almost equally developed female reproductive branches with spines in the tubular portion of the uterus, a body length of 3.67–4.25 mm, a flat lip region, rounded cephalic region, separated from body contour by a shallow depression, a spear 215–225 μm long, mid-body diameter of 60–79 μm, vulva (46–48%), a short tail (30–38 µm, c = 103–133, c′ = 0.7–0.9), conoid, dorsally convex, ventrally directed with a small terminal peg and a distinct terminal blind canal, the presence of four juvenile stages and the absence of males. The polytomous identification codes of the new species are: A4, B3, C5a, D6, E5, F4, G3, H2, I3, J4, K2, L1. In addition to morphological and morphometric data, molecular analyses of the D2–D3 expansion regions of the 28S rDNA gene placed the new species as a sister species of (Group 5) with 65% Bayesian posterior probability and further separated this species from the other members in group 6. In this study, , and were also collected and additional data for the species were provided.