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Two rare species of the family Tylenchidae are described and illustrated based on morphological and morphometric characters. Scanning electron microscope (SEM) studies provided details of anterior end structures, helpful in generic identification of the studied populations. Discotylenchus biannulatus n. sp. is characterized by its dorso-ventrally flattened smooth cephalic region having two proximal annuli and a rectangular perioral disc, short longitudinal amphidial slits, lateral field with four incisures, stylet 9-10 μm long, with the conus shorter than half the total stylet length and with posteriorly directed knobs, well-developed median bulb, mono-prodelphic reproductive system with rounded empty spermatheca and short postvulval uterine sac (PUS), and filiform tail with pointed end. It is compared with other species of Discotylenchus having four lines in the lateral field. The Iranian population of Labrys chinensis is characterized by its long and slender (a = 45.2-57.2) body, smooth rounded cephalic region and an offset disc-like apical labial plate, short longitudinal lateral amphidial slits, lateral field with two incisures, moderately developed stylet with the conus less than half the total length and posteriorly directed knobs, median bulb fusiform with distinct but weak valve, gradually joining the isthmus, vulva at 57.2-59.1% with small flaps, elongate conoid tail, uniformly and slightly narrowing toward end with broadly rounded terminus and rare males. The minor morphological differences of the recovered population with the type population are discussed.

Veleshkinema  iranicum n. gen., n. sp. is described and illustrated based on morphological, morphometric and molecular characters. The new genus is characterized by having slender females and males, stylet with asymmetrical knobs, dorsal gland orifice just posterior to subventral knob, lip region with flattened apex and eight sectors, pharynx with a non-muscular and non-valvular median bulb, pharyngeal glands slightly overlapping intestine dorsally, visible cellular cardia, female with a single gonad having a quadricolumellate crustaformeria with 8-10 cells in each column, no postvulval uterine sac and rounded and offset spermatheca containing spheroid sperm cells, males with arcuate tylenchoid spicules and subterminal bursa. The new genus is morphologically compared with four genera: Abursanema, Deladenus, Prothallonema and Sphaerularia. Molecular phylogenetic studies of the new genus using 808 bp partial sequences of SSU ribosomal RNA gene placed the new genus in a clade with Sphaerularia spp. In phylogenetic analyses using 756 bp partial sequences of the 28S ribosomal RNA gene (D2-D3 segments), the new genus formed a monophyletic group with Abursanema iranicum and Sphaerularia spp.

Two populations of the genera Trischistoma and Tripylella were recovered from the rhizosphere of grapevines and mosses growing on alder trees in Zanjan and Guilan provinces, respectively, Iran. The nematodes were identified as Trischistoma abharensis n. sp. and Tripylella intermedia, respectively. Trischistoma abharensis n. sp. is characterized by having females with body length 1069-1322 μm, presence of sparse somatic setae on the sublateral body, absence of ventromedian cervical setae, a distinct dorsal tooth directed anteriorly, absence of post-vulval uterine sac, and tail with one pair of subdorsal caudal setae. Males were not found. Tripylella intermedia is characterised by having females with body length 905-990 μm, annulated cuticle, stoma with two chambers: with dorsal tooth lying in posterior buccal chamber, and one large subventral and one small subventral tooth, respectively lying in posterior and anterior buccal chambers, cardiac glands large, composed of six fused cells, and tail 121-155 μm long, ventrally bent, anterior half broad, then suddenly narrowing, with posterior half tapered narrowly and cylindrically. The phylogenetic relationships of both species were analysed using sequences of the partial small subunit (SSU) and D2/D3 expansion segments of large subunit (partial LSU) of ribosomal RNA genes and are discussed.

A new species of the genus Sectonema, collected from natural forests in the Spanish provinces of León and Palencia, is described and illustrated with line drawings and LM pictures. Sectonema septentrionale sp. n. is characterized by its 5.59-6.90 mm long body, lip region 25-29 μm broad and offset by deep constriction, mural tooth 18-19 μm long at its ventral side and occupying most of the stomatal lumen, pharyngeal expansion 618-926 μm long or 60-73% of total neck length, uterus tripartite and 370-493 μm long or 2.9-4.3 times the corresponding body diameter, V = 48-52, tail short and rounded (40-62 μm, c = 108-146, c' = 0.6-0.8), spicules 100-145 μm long, and 5-11 irregularly spaced ventromedian supplements with hiatus. It is very close to S. demani, but differs both in the nature of the mural tooth and of the uterus.

Three new and one known species of the genus Aporcelaimellus with simple uterus and typical caudal region, mainly col-lected in natural areas of southeastern Iberian Peninsula, are studied, including descriptions, measurements, line illustrations and LM pictures. Aporcelaimellus baeticus sp. n. is characterized by a body length of 1.96-2.95 mm, lip region offset by constriction and 17-20 μm broad, odontostyle 17-22 μm long, neck 510-635 μm long, pharyngeal expansion 250-335 μm long, a dorsal cell mass at level of anterior end of intestine, uterus 60-150 μm long or 0.9-1.7 times the corresponding body diameter, vulva transverse (V = 48-54), tail convex conoid with broadly rounded terminus (30-46 μm, c = 47-80, c' = 0.7-1.1), spicules 99-103 μm long, and 18-21 irregularly spaced ventromedian supplements which lack hiatus. Aporcelaimellus brevicaudatus sp. n. is characterized by a body length of 1.54-2.14 mm long, lip region offset by a more or less distinct constriction and 14-16 μm broad, odontostyle 13-15 μm long, neck 512 μm long, pharyngeal expansion 255 μm long, uterus 39-57 μm long or 0.9-1.0 times the corresponding body diameter, V = 50-55, tail short and rounded to hemispherical (24-27 μm, c = 66-82, c' = 0.6-0.7) with inner core hardly reaching the middle of tail length, and male unknown. Aporcelaimellus rotundus sp. n. is characterized by its body 2.01-2.58 mm long, lip region offset by constriction and 19-20 μm broad, odontostyle 22-23 μm long, neck 455-579 μm long, pharyngeal expansion 226-316 μm long, a dis-tinct dorsal cell mass present at cardia level, uterus 28-74 μm long or 0.5-0.9 times the corresponding body diameter, V = 47-52, female tail short and conoid to rounded (27-33 μm, c = 64-90, c' = 0.7-0.9), and males unknown. New data, including SEM pictures, sequences and taxonomic comments, are provided for A. waenga.

The taxonomy of the genus Aporcelaimellus is revised and updated. A new definition is proposed, with several remarkable diagnostic characters: cuticle three-layered, especially distinguishable at caudal region, usually bearing a hyaline space between inner and intermediate layers at terminal portion of tail; cervical lacunae often present and well developed; oral aperture a dorso-ventral, hexagonal open slit; lip region showing bilateral symmetry and offset by a more or less distinct constriction; odontostyle short, robust and with wide aperture; uterus simple, bi- or tripartite; pars refringens vaginae present, well developed; tail similar in both sexes, short, rounded to conical with more or less rounded terminus; and ventromedian supplements 7-25 in number, separated, almost always with precloacal space (hiatus). A list of 28 valid species and their synonyms is provided as well as a key to their identification and a tabular compendium of their morphometrics. Aporcelainiellus faridpuriensis is considered to be a species inquirenda. Twenty-one species are regarded as incertae sedis: A. amplexor, A. budauniensis, A. canis, A. digicaudatus, Dorylaimus domus glauci, A. estonicus, A. gerlachi, A. goldeni, A. index, A. jairajpurii, A. monodelphus, A. nawabganjense, A. nivalis, A. paracentrocercus, A. paraobtusicaudatus, A. radicus,A. sacchari, A. seinhorsti, A. stilus, A. submissus and A. subsimilis. Two species are retained under other genera: A. bicuticulus under Labronema, and A. cocophilus under Aporcelaimus. Sixteen species are transferred to other genera: A. baqrii and A. odhneri to Crassolabium; A. dubius to Discolaimium as Discolaimium geraldi nom. n.; A. duhouxi to Labronema; A. glandus, A. heynsi, A. maitai and A. paraconicaudatus to Discolaimiun; A. insularis, A. jiaonanensis, A. kikereensis and A. propinquus to Aporcelinus; A. maximus to Aporcella; A. paracentrocercus apud Andrássy (1960) to Aporcelinus as Aporcelinus africanus sp. n.; A. saprophilus to Eudorylaimus; and A. tritici to Makatinus. Finally, A. concavus becomes a non-valid binomen.

Three new and one known species of the genus Aporcelaimellus, collected mainly in natural areas from the Iberian Peninsula and characterized by having a simple uterus and atypical caudal region are described and illustrated, including line drawings, LM pictures and/or SEM pictures. Aporcelaimellus deserticola sp. n. is distinguished by its body 1.79-2.43 mm long, lip region 14-16 pm broad and offset by expansion rather than by constriction, odontostyle 18-21 µm long, neck 464-555 µm long, pharyngeal expansion 234-283 µm long or 49-52% of total neck length, a dorsal cell mass present at level of anterior end of intestine, uterus 34-67 µm long or 0.6-1.1 times the corresponding body diameter, V= 49-55, tail conical with rounded terminus (29-43 µm, c = 47-66, c' = 0.9-1.4) and bearing a short but perceptible hyaline portion, and male unknown. Aporcelaimellus hyalinus sp. n. is characterized by its body 1.49-2.23 mm long, lip region offset by constriction and 13-16 µm broad, odontostyle 14-16 µm long, neck 389-474 µm long, pharyngeal expansion 183-242 µm long or 45-53% of total neck length, uterus 44-106 µm long or 0.7-1.8 times the corresponding body diameter, V = 48-55, tail conical with rounded terminus (27-41 µm, c = 38-68, c' = 1.0-1.4) and short inner core, spicules 56 µm long, and seven irregularly spaced ventromedian supplements. Aporcelaimellus rarus sp. n. is distinguished by its body 1.96-2.34 mm long, lip region offset by constriction and 14-16 µm broad, odontostyle 15-16 µm long, neck 411-518 µm long, pharyngeal expansion 196-270 µm long or 48-52% of total neck length, a dorsal cellular mass at a short distance behind the cardia, uterus 63-96 µm long or 0.8-1.5 times the corresponding body diameter, V= 51-56, female tail short and conical (28-40 µm, c = 50-74, c' = 0.7-0.9) with rounded terminus and bearing a dorsal concavity at its posterior half, and males unknown. New data are provided for A. salicinus. A discussion of these atypical species is also provided.