Summary A new species belonging to the genus Aporcella, collected in cultivated soils of East Azarbaijan province, Iran, is described and illustrated. The new species is characterised by its 1.08 (1.05-1.15) mm long body, two-layered cuticle, lip region offset by constriction and 12 (11-13) μm broad, odontostyle 13.0 (12.5-14.0) μm long or nearly equal to lip region diam., neck 310 (293-325) μm long, pharyngeal expansion 137 (128-144) μm long, occupying 43-45% of the total neck length, female genital system didelphic-amphidelphic, uterus simple, 34-48 μm long, vulva transverse (V = 59 (58-61)), tail conical with finely rounded terminus (30 (29-33) μm long, c = 34 (33-36), c′ = 1.5 (1.4-1.6)), and male absent. Molecular analyses, using Bayesian inference based on partial LSU sequences, confirm the monophyly of Aporcella as well as its clustering with other dorylaimid taxa characterised by the absence of pars refringens vaginae. The taxonomy of the genus is updated, with an emended diagnosis, list of species, key to their identification, and a compendium of the main morphometrics of species/populations described since the last available revision.

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A new species of the genus Metaxonchium is described from natural habitats in Iran. The new species is characterized by having body length of 2.46-3.12 mm, lip region offset by constriction and 8-11 µm wide, odontostyle fusiform and 10-12 µm long, neck 773-1150 µm long, anterior portion of pharynx bearing a spindle-shaped thickening with valve-like structures inside, both parts of the pharynx separated by a short isthmus-like narrowing, pharyngeal expansion 531-825 µm long and occupying up to three-fourths of total neck length, female genital system monodelphic-opisthodelphic, anterior genital branch reduced to a large uterine sac and a small terminal mass, posterior uterus long and tripartite with an intermediate region bearing apophyses, V = 53-57, caudal region conoid with broadly rounded terminus (24-35 µm, c = 79-105, c' = 0.6-0.9), spicules 92-103 µm long and 7-10 spaced ventromedian supplements, at least two of them within the range of spicules. The taxonomy of the genus Metaxonchium is updated, including a list of its species, a key to their identification and a compendium of their morphometrics. Four species are transferred from Axonchium to Metaxonchium: M. coxi, M. japonicum, M. mizukuboi and M. zealandicum.

Three Iranian populations of Discolaimium dubium are studied, including their morphological and morphometric characterization, molecular analysis (LSU-rDNA) and the description of the male for the first time. For comparative purposes, this species is distinguished by its 1.10 to 1.40 mm long body, lip region offset by constriction and 8 to 10 µm wide, odontostyle 7.5 to 10.5 µm long with aperture occupying 59 to 76% of total length, neck 300 to 362 µm, pharyngeal expansion 127 to 181 µm long or 44 to 46% of the total neck length, uterus simple and 38 to 53 µm or 1.2 to 1.5 times the body diameter long, V = 52 to 58, tail conical (32-38 µm, c = 32-43, c′ = 1.6-2.0) with rounded tip and a hyaline portion occupying 14 to 15% of tail length, spicules 30 to 32 µm long, and two or three widely space ventromedian supplements with hiatus. Both morphological and molecular data support its belonging to the genus Aporcella, whose monophyly is confirmed and to which the species is formally transferred as A. dubia (Das et al., 1969) comb. n.

A new species of the genus Crassolabium, Crassolabium persicum sp. n., collected from Arasbaran rangelands of Iran, is described and illustrated. It is characterized by its body 1.92–2.40 mm long, lip region offset by constriction and 17–19 μm wide, odontostyle 16–19 μm long with aperture occupying less than one–third (27–30%) its length, neck 428–690 μm long, pharyngeal expansion 369–390 μm long or occupying 54–56% of total neck length, female genital system amphidelphic, uterus bipartite and 162–218 μm long or 2.3–3.5 times as long as body diameter, pars refringens vaginae well developed, V = 54–57.5, vulva longitudinal, prerectum bearing a blind sac, tail conical with rounded tip to conoid (25–36 μm, c=60–69, c’=0.5–0.9), spicules 68–72 μm long, precloacal pair of supplements far (22–27 μm) from cloacal aperture, and 13–17 shortly spaced ventromedian supplements with hiatus. The new taxon is compared in depth to its relatives in Crassolabium as well as other similar species of Aporcelaimellus and Amblydorylaimus.