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Eudorylaimus kahaqensis sp. n. (Figs 1–6) Material examined: Twenty females, twelve males and several juveniles, in acceptable (mostly good) condition. Measurements: See Table 1. Description. Adult: Slender nematodes (a = 29–39) of medium size, 1.40–1.75 mm long. Body cylindrical, tapering towards both ends as the tail is conical. Habitus regularly curved ventrad, an open ‘C’ or ‘J’ shape in females, ‘J’ or ‘G’ shaped in males. Cuticle 2.0–2.5 µm thick in the anterior region, 2.0–3.5 µm at mid-body and 3.0–4.0 µm on tail; outer layer with fine transverse striation throughout the body, perceptible even under LM; inner layer thicker than the outer one, especially visible at caudal region. Lip region anteriorly truncate, nearly continuous with the adjacent body, 2.8–3.2 times as wide as high, and ca one half (45–50%) of body diameter at neck base; anterior margin visibly corrugated or wrinkled. SEM observations: lips totally amalgamated; labial and cephalic papillae distinct but weakly protruding, button-like; oral field broad, with coarse radial striation—visibly stronger than the transverse striation of the adjacent body, and responsible for the corrugated anterior marginrunning from the oral aperture to the posterior margin of lip region; oral aperture apparently small. A moderately sclerotized but perceptible cephalic framework is present. Amphidial fovea stirrup-shaped, aperture a transverse slit 9–11 µm wide and occupying ca one-half (50–56%) of lip region diameter. Cheilostom wider than usual, with convex walls. Odontostyle equal to lip region diameter long, comparatively slender (9–12 times as long as wide), 1.1–1.3% of total body length, and with aperture 6–8 µm long or occupying less than one-half (33–44%) of total length. Guiding ring simple, somewhat plicate, and located at 8–11 µm or 0.4–0.5 times the lip region diameter from the anterior end. Odontophore rod-like, 1.7–2.0 times the odontostyle in length, its junction with the pharyngeal lining rather inconspicuous. Anterior portion of pharynx slender but muscular, enlarging very gradually into the basal expansion that is 7.4–9.0 times as long as wide, 4.0–4.6 times as long as the body diameter at neck base and occupies 45–53% of total neck length; gland nuclei located as follows: DO = 60–66, DN = 66–70, S1N1 = 78–83, S1N2 = 82–88, S2N = 90–94, S2O = 94; DN remarkably posterior in position, far from pharyngeal enlargement, S1N1 conspicuously longer than wide, with its nucleolus much larger than that of S1N2 and even slightly larger than those of S2N, and S2O visibly behind S 2N. Nerve ring at 128–145 µm or 35–37% of the neck length from the anterior end. One coelomocyte 7.5– 13 x 5.5–10.0 µm is present in dorsal position in all the specimens examined a short distance behind the nerve ring, at 145–162 µm from the anterior end. Cardia cylindroid, 13.5–19.0 x 7.0–8.5 µm. A dorsal cell mass is always present at the pharyngo-intestinal junction. Intestine without any special differentiation. Female: Genital system didelphic-amphidelphic, with both branches of similar morphology and length, the anterior 192–264 µm or 11–14% of total body length, the posterior 182–273 µm or 12–14% of total body length. Ovaries reflexed, 77–101 µm long, not reaching the oviduct-uterus junction; oocytes in several rows in the germinative zone, then in one row. Oviduct 84–120 µm or 2.0–2.8 times the corresponding body diameter long, consisting of a slender portion made of prismatic cells and an appreciably longer than wide pars dilatata with visible lumen and often containing sperm cells. A marked narrowing surrounded by a weak muscular ring is present separating oviduct and uterus. Uterus a simple tube-like structure 62–125 µm or 1.5–2.3 times the corresponding body diameter long, often containing sperm cells as well. Vagina 26–33 µm long, extending to 63– 70% of body diameter: pars proximalis 18–24 x 16 –22 µm, with somewhat sigmoid walls and surrounded by moderately developed musculature; pars refringens consisting of two trapezoidal pieces 3.0–3.5 x 7.0–7.5 µm and a combined width of 15–18 µm; pars distalis 5.5–6.5 µm long. One gland cell (granular in appearance) is present close the vagina both anteriorly and posteriorly. Vulva a transverse slit. Intestine-prerectum junction especially granular and colored in all the specimens examined. Prerectum 1.4–1.6, rectum 1.1–1.2 times the anal body diameter in length. Caudal region regularly curved ventrad and conical (somewhat) elongate with finely rounded tip; hyaline portion well developed, 17–30 µm or 28–45% of the total tail length. Male: Genital system diorchic, with opposite testes. In addition to the ad-cloacal pair situated at 11–15 µm from the cloacal aperture, there is a series of 7–9 irregularly spaced (12–15 µm apart), ventromedian supplements, the most posterior of which is located at 22–28 µm from the ad-cloacal pair, at the level of or a short distance behind the anterior end of spicules. A distinct pre-cloacal space (hiatus) is therefore not present. Spicules dorylaimid, 1.7–1.9 times longer than the body diameter at level of cloacal aperture, 3.9–4.2 times longer than wide, and curved ventrad 124–130º; head 12–16 µm long, occupying 23–30% of total spicule length, 2.0–2.3 times as long as wide, with its dorsal side distinctly longer than the ventral one and slightly curved; median piece 35–41 µm long, 6.4–7.6 times longer than wide, occupying 37–46% of spicule width, and reaching the spicule posterior tip. Lateral guiding piece 13–17 µm long, 5.2–6.8 times longer than wide, with slightly bifid end. Prerectum 1.8– 2.5, cloaca 1.4–1.7 times the body diameter at level of cloacal aperture. Caudal region similar to that of female, its hyaline portion 22–25 (11.5 in one specimen, probably aberrant) µm long, occupying 39–40 (26)% of total tail length. Diagnosis. The new species is characterized by its 1.40–1.75 mm long body, lip region nearly continuous and 17–21 µm wide and bearing a weakly sclerotized but distinct cephalic framework, cheilostom broad and with convex walls, odontostyle 21–23 µm long with aperture occupying 33–44% of its length, presence of a dorsal coelomocyte a short distance behind the nerve ring, neck 347–397 µm long, DN rather posterior (66–70%), pharyngeal expansion 162–205 µm or occupying 45–53% of total neck length, presence a dorsal cell mass at level of pharyngo-intestinal junction, V = 48–52, caudal region conical (somewhat) elongate (50–73 µm, c = 24–30, c’ = 1.9–2.6 in females, 45–68 µm, c = 22–32, c’ = 1.7–2.3 in males) and regularly curved ventrad with large hyaline portion, spicules 48–55 µm long and 7–9 irregularly spaced ventromedian supplements lacking hiatus. Relationships. Eudorylaimus kahaqensis sp. n. is easily recognizable by an unusual combination of features, but its conical, somewhat elongate, caudal region in both sexes and the position of its most posterior ventromedian supplement at the level of the anterior end of the spicules and not too far anterior to the pre-cloacal pair (i. e., lacking a distinct hiatus) raise doubts about its true generic identity (see further discussion below), since it possesses characteristics of the genera Eudorylaimus Andrássy, 1959, Allodorylaimus Andrássy, 1986 and Epidorylaimus Andrássy, 1986. Within Eudorylaimus, it resembles several species (some without known males), in particular E. altherri Tjepkema et al., (1971), E. nudicaudatus Heyns, 1993 and E. unicus Khan & Araki, 2000. It differs from E. altherri in its nearly continuous (vs offset by constriction and visibly wider than the adjacent body) lip region, longer odontostyle (21–23 vs 19.3 ± 1.2 µm), shorter female prerectum (43–50 vs 90 ± 22 µm), pars refringens vaginae with trapezoidal (vs triangular) pieces, and male as frequent as female (vs male absent). From E. nudicaudatus, it differs in its nearly continuous (vs offset by constriction) lip region, longer odontostyle (21–23 vs 13–15 µm, equal to vs distinctly shorter than lip region diameter), more posterior vulva (V = 48–52 vs V = 43–48), comparatively longer female tail (c = 24–30 vs c = 32–46) with long (vs very short) hyaline portion, and male lacking (vs having) hiatus. It can be distinguished from E. unicus by its nearly continuous (vs offset by constriction) lip region, more posterior DN (vs close the pharyngeal expansion), longer vagina (extending to 63–70% vs up to one-half of body diameter), longer female tail (c’ = 1.9–2.6 vs c’ = 1.6–1.8) with different morphology (ending in a finely rounded vs relatively coarse tip), and male present (vs absent). The new species also resembles E. rugosus (Andrássy, 1957) Andrássy, 1959 in several aspects (general morphology and morphometry, lip region nearly truncate and visibly slender odontostyle) but differs in its longer tail (c = 24–30, c’ = 1.9–2.6 vs c = 30–33, c’ = 1.5–1.6). It can also be compared to E. pseudobokori Zell, 1986 in its general morphology and morphometry as well its comparatively long caudal region, but can be distinguished by the morphology of lip region (truncate and continuous vs angular and offset) and odontostyle (slender vs more robust), and the number (7–9 vs 5) and arrangement of ventromedian supplements (most posterior of them at level of or slightly posterior to vs visibly anterior to the end of spicules). In lacking a distinct precloacal space in males, the new species also resembles members of Allodorylaimus, especially A. aljabaranus Quijano et al., (1991) and A. digiturus (Thorne, 1939) Andrássy, 1986. It differs from A. aljabaranus in its broader (17.0–21 vs 14–16 µm) and amalgamated (vs lips separated and angular) lip region, and fewer ventromedian supplements (7–9 vs 10–15) with different arrangement (only the most posterior ventromedian supplement located at the level of the anterior end of the spicules or a short distance posterior vs two or three ventromedian supplements well within the range of the spicules). From A. digiturus, a poorly known species described on the basis of only one male, it differs in its larger general size (body length 1.40–1.75 vs 1.30 mm), broader lip region (17.0–21 vs ca 12 µm), longer (21–23 vs ca 12 µm) and more slender (9–12 vs ca 6 times as long as wide) odontostyle, and fewer ventromedian supplements (7–9 vs 11) with different arrangement (only the most posterior ventromedian supplement located at the level of the anterior end of the spicules or a short distance behind it vs two ventromedian supplements well within the range of the spicules). In its general morphology, and in particular in its comparatively long tail in both females and males, and males lacking hiatus, the new species resembles some Epidorylaimus representatives (see the updated diagnosis and compendium by Ahmad et al., 2016), especially E. consobrinus (de Man, 1880) Andrássy, 1986 and E. filicaudatus (Tjepkema et al., 1971) Andrássy, 1986. The new species differs from E. consobrinus, a poorly characterized species, in its weakly (vs distinctly) angular lip region, and shorter caudal region (c’ = 1.9–2.6 vs c’ = 2.7–4.3 in females) with different morphology (with finely rounded vs acute tip, large vs no hyaline portion). It can be distinguished from E. filicaudatus by having weakly (vs distinctly) angular lip region, more attenuated odontostyle (9–12 vs up to 7 times as long as wide), shorter caudal region (50–73 vs 81–123 µm), and frequent males (vs male unknown). Finally, some traits (continuous lip region, broad cheilostom) of the new species resemble those found in species of the genus Chrysonema Thorne, 1929, but it does not fit at all the very peculiar morphological pattern of this taxon (see Andrássy, 2009), which is characterized by, among other diagnostic features, a very slender body (a - ratio very usually over 50), comparatively small and attenuate odontostyle, absence of pars refringens vaginae, tail conical elongate (c’ > 4), tapering very gradually, and male bearing subventral caudal papillae. Type locality and habitat. The new species has been collected from Iran, East Azarbaijan province, north of Maragheh, Kahaq region (GPS coordinate 47º13´35.7´´E, 37º28´12.1´´ N), where it was found in the rhizosphere soil of walnut, spruce and willow. Type material. Female holotype, 10 female and eight male paratypes deposited in the Nematode Collection of Nematology Laboratory, Department of Plant Protection, Faculty of Agriculture, University of Tabriz, Tabriz, Iran. Two female and two male paratypes with the Nematode Collection, University of Jaén, Spain. Etymology. The specific epithet refers to the geographical origin of the new species in Kahaq region, Iran. Remarks. The new species herein described is an excellent example of the problematic taxonomy of the conical-tailed species of the family Qudsianematidae. It is characterized by a combination of features that allows its relatively easy identification but that, at the same time, raises doubt about its generic identity. Its conical, somewhat elongate caudal region is intermediate between those observed in species of Eudorylaimus, which tend to be shorter, and those of Epidorylaimus species, which tend to be longer, but there is no distinct borderline between the two genera. The location of the posteriormost ventromedian supplement is also notable: situated at approximately the level of the anterior end of the spicules, it is not too much farther from the adcloacal pair than from the penultimate ventromedian supplement of the series, so that a pre-cloacal space (hiatus) is not distinctly perceptible, again representing an intermediate condition between Eudorylaimus (males with distinct hiatus) and Allodorylaimus and Epidorylaimus (both with males lacking hiatus, i.e. with one or more ventromedian supplements within the range of the spicules). With due caution, the new species has been provisionally classified under Eudorylaimus because its general morphology fits better the pattern of that genus. Nevertheless, leaving aside the tail length and the presence/absence of a hiatus, it should be emphasized that the new species displays other features (nearly truncate and continuous lip region with corrugated anterior margin, broad cheilostom, weakly sclerotized but perceptible cephalic framework, presence of a coelomocyte shortly behind the nerve ring, dorsal gland pharyngeal nucleus in rather posterior position, etc.) that conform a peculiar pattern that might deserve separate generic status if other species are found that share it.

Peña-Santiago, R., Niknam, G., Álvarez-Ortega, S., Jabbari, H. (2014): Metaxonchium persicum sp. n. from Iran (Nematoda, Dorylaimida, Belondiridae), with an updated taxonomy of the genus. Zootaxa 3785 (4): 501-517, DOI: http://dx.doi.org/10.11646/zootaxa.3785.4.1

Sectonema demani Altherr, 1965 (Figs 1���3) Material examined. Female holotype, in bad condition as the nematode has become broken into four parts, but some relevant morphological features are distinguishable. One female from Brabant (Belgium), in excellent condition. Measurements. See Table 1. Prerectum length 288 314 ?? 182? Rectum���Cl��aca length 70 85 ?? 75 84 ��ail length 51 55 32 54 62 58 Spicule length - - - - - 107 ventr��median supplements - - - - - 8 Calculated fr��m ��riginal descripti��n. Description. Female holotype (Fig. 1): Slender nematode of large size, estimated at 7.24 mm long. Body cylindrical, distinctly tapering towards the anterior end, less so towards the posterior one because the caudal region is rounded. Habitus regularly curved ventrad after fixation, probably C-shaped. Cuticle three-layered, especially distinct at caudal region, consisting of thin and smooth outer layer, a very thicker intermediate layer bearing radial striation, and a thin inner layer; thickness 4.5 ��m at anterior region, 5.5 ��m in mid-body and 13 ��m on tail. Lateral chords obscure. Body pores distinct, four lateral ones at cervical region, at 9, 37, 72 and 79 ��m from the lip region constriction. Lip region nearly truncate, offset by deep constriction, 3.7 times as wide as high and 23 % of body diameter at neck base; lips separate; labial and cephalic papillae distinct but low, weakly protruding. Amphid fovea not observed as the anterior region is seen in ventral view. Cheilostom apparently as long as wide since the guiding ring is not perceptible. Ventral side of mural tooth ca three-fourths (74 %) of lip region diameter long or 0.28 % of body length. Odontophore rod-like, without any differentiation. Pharynx distinctly muscular and tripartite, consisting of an anterior thickened spindle-shaped region, a narrower intermediate section enlarging very gradually, and a basal expansion 11.2 times as long as wide, 7.4 times as long as body diameter and occupying 68 % of total neck length. Pharyngeal gland nuclei obscure. Nerve ring also obscure. Morphology of cardia not distinguishable. Genital system didelphic-amphidelphic, but some details of its morphology remain difficult to elucidate: ovaries large, barely surpassing the oviduct-uterus junction; oviduct ca 310 ��m long or 2.1 times (probably more as the specimen is visibly flattened) the corresponding body diameter, with an elongate pars dilatata; oviduct-uterus junction marked by a distinct narrowing; uterus apparently a simple tube-like structure ca 270 ��m long or 1.8 times the corresponding body diameter; pars refringens vaginae seems to be present and welldeveloped; vulva (as observed in ventral view) a long transverse slit. Prerectum 3.8, rectum 0.9 anal body diameters long. Caudal region short and rounded, slightly more convex at its dorsal side; inner core weakly protruding at tail tip. Caudal pores two pairs, subdorsal, at the middle of tail. Male: Unknown. One female from Brabant, Belgium (Figs 2 & 3): Comparatively very slender (a = 56) and large nematode, 6.78 mm long. Body cylindrical, distinctly tapering towards the anterior end, less so towards the posterior one because the caudal region is rounded conoid. Habitus regularly curved ventrad after fixation, C-shaped. Cuticle three-layered, especially obvious at caudal region, consisting of a thin and smooth outer layer, a thick intermediate layer bearing radial striation and fine criss-cross lines through the entire body (Fig. 3 K), and thinner inner layer; thickness 4 ��m at anterior region, 5.5 ��m in mid-body and 13 ��m on tail. Lateral chord 20 ��m wide at mid-body, occupying about one-seventh (17 %) of mid-body diameter. Body pores distinct, three dorsal and three ventral pores at level of the mural tooth plus odontophore. Lip region offset by deep constriction, 3.7 times as wide as high and ca one-fourth (24 %) of body diameter at neck base; lips separate, their inner region probably differentiated in perioral lobes; labial and cephalic papillae distinct but low, weakly protruding. Amphid fovea cup-shaped, opening at level of the cephalic constriction and occupying 12 ��m or hardly less than one-half (45 %) of lip region diameter. Cheilostom nearly cylindrical, lacking any differentiation. Ventral side of mural tooth straight, 3.3 times longer than its width at the base, and 0.7 times the lip region diameter long or 0.29 % of total body length; dorsal side sigmoid, slightly longer than the ventral one and visibly refractive at its base; mural tooth base 6 ��m wide, visibly narrower (60 %) than the stomatal lumen. Guiding ring weak, very plicate, at 13 ��m or 0.5 times the lip region diameter from the anterior end. Odontophore linear, rod-like, ca twice (2.1 times) the mural tooth length. Pharynx typical of the genus, tripartite, consisting of a comparatively thick anterior region, a short narrower intermediate part (enveloped by the nerve ring) enlarging very gradually, and the basal expansion 13.2, times as long as wide, 7.2 times as long as body diameter, and occupying 69 % of total neck length. Pharyngeal gland nuclei located as follows: DN = 44; S 1 N 1 = 65; S 1 N 2 = 76; S 2 N = 87. Nerve ring located at 270 ��m from the anterior end or at 22 % (n = 2) of total neck length. Cardia rounded conoid, 16 x 23 ��m, its junction to pharyngeal base surrounded by a thick ring-like structure; intestine enveloping the cardia at about its middle and forming a short conical extension protruding into the intestinal lumen. Intestine cells especially distinct, six to eight in diameter, with very well perceptible membrane, nucleus and protoplasmic granules (Fig. 3 J). Many granular, pseudocoelomocyte bodies present at the posterior body region, predominantly in lateral and dorsal position (Fig. 3 L). Genital system didelphic-amphidelphic, with both branches almost equally and well developed, the anterior 553 ��m long or 8 % of total body length and the posterior 563 ��m long or 8 % of total body length: ovaries relatively small, not reaching the level of the oviduct-uterus junction, the anterior 186, the posterior 193 ��m long, with oocytes arranged first in two or more rows, then in a single row; oviduct 243���248 ��m long or 2.0��� 2.1 times the corresponding body diameter, and consisting of a slender part with prismatic cells and a well developed pars dilatata with perceptible lumen; oviduct-uterus junction marked by a very distinct narrowing surrounded by a muscular ring; uterus a simple, tube-like structure 248���267 ��m long or 2.1���2.2 times the corresponding body diameter; vagina extending inwards 85 ��m or 71 % of body diameter, with pars proximalis 60 x 51 ��m, somewhat sigmoid walls and surrounded by weak musculature, pars refringens with two close together trapezoidal pieces measuring 22 x 18 ��m and a combined width of 37 ��m, and pars distalis 6 ��m long. Vulva a nearly equatorial transverse slit. Prerectum 4.4, rectum 1.2 anal body diameters long. Tail short, rounded conoid, slightly straighter at its ventral side; inner cuticle layer showing a gap (more transparent area) at tail tip. Caudal pores two pairs, one sublateral, another subdorsal, at the middle of tail. Diagnosis (based on female holotype and the Belgian female). This species is characterized by its 6.78���7.24 mm long body, lip region offset by deep constriction and 27���28 ��m broad, mural tooth 19���20 ��m long at its ventral side and 21 ��m at its dorsal one with its base 6 ��m wide or three-fifths of the stomatal lumen, neck 1217���1290 ��m long, pharyngeal expansion 834���875 ��m long or 68���69 % of total neck length, female genital system didelphicamphidelphic, uterus a simple tube-like structure measuring 248���270 ��m long or 2.1���2.2 times the corresponding body diameter, pars refringens vaginae well developed, V = 49���52, tail short and rounded conoid (51���55 ��m, c = 123���143, c��� = 0.7���0.8), and male unknown. Relationships. Sectonema demani morphometrically resembles S. ventrale Thorne, 1930, but it can be easily distinguished from this in the nature and size of its stomatal protruding structure (vs a reduced odontostyle rather than a mural tooth, 12���14 ��m long, with its base occupying nearly the whole stomatal lumen, according to the recent re-description by Pe��a-Santiago & ��lvarez-Ortega, in press). It is also similar to S. paramonovi (Eliava, 1966) Eliashvili, Aliev & Eliava, 1977, a poorly characterized species, originally described on the basis of only one male specimen. Sectonema demani and S. paramonovi may be identical but available information (based on different sexes) does not allow their detailed comparison. Type locality and habitat. Germany, Rhine river near Krefeld, in groundwater; collected on October 29 th, 1958. Other localities and habitats. Hungary, near Budapest, H��rsbokorhegy, in the soil of an oak forest (Andr��ssy, 1984, 1990, 2009). Belgium, province of Brabant (present study). See also remarks regarding one other suspected record by de Man (1921) from the Netherlands. Type material. Female holotype on slide labelled NE 287, deposited with E. Altherr���s nematode collection at the Museo Cantonale di Storia Naturale���Lugano, Switzerland. Remarks. The above description of female holotype perfectly fits the original one by Altherr (1965), but very small morphometric differences can be noted, certainly due to subjective perception and/or the use of different microscopic devices. Loof (1961) considered that the female specimen described by de Man (1921) from the Netherlands as Dorylaimus robustus might belong to an undescribed species of Sectonema. In his turn, in describing the new species S. demani, Altherr (1965) discussed that de Man���s female might be identical with his new species as their respective morphometrics are very similar. A comparative analysis (see Table 1) shows that the female reported by de Man actually is nearly identical morphometrically to Altherr���s holotype, but also that its caudal region is significantly shorter (32 vs 51 ��m, c = 143 vs c = 225, c��� = 0.4 vs c��� = 0.7). Thus, some doubt persists on the true identity of this specimen, which might rather belong to S. brevicauda Heyns, 1965. Andr��ssy (1984, 1990, 2009) reported the presence of S. demani in Hungarian soils, but no description of this material was provided by the author. The female from Brabant has been tentatively regarded as being conspecific with the holotype since, as far as they can be compared���as mentioned, the holotype is in bad condition and its anterior region is not observed in lateral view, actually a handicap for comparative purposes���their main diagnostic features (lip region, mural tooth, female genital system, caudal region, etc.) are nearly identical, their morphometrics are very similar, and both occur in West Central Europe (Germany and Belgium, respectively). The mural tooth of S. demani, as observed in the Brabant female, differs from that found in S. ventrale, the type species of the genus (see details in Pe��a-Santiago & ��lvarez-Ortega, in press) in two main aspects. First, its dorsal side is slightly sigmoid (vs forming a perceptible concavity or nearly right angle at its posterior part) and visibly (vs hardly) longer than the ventral one. Second, and more importantly, it is conspicuously narrower (ca 60 %, see above) than the stomatal lumen as the dorsal side does not join the dorsal wall of the stoma at all. Thus, it should be regarded as a true mural tooth (vs a reduced odontostyle in contrast to a typical mural tooth in S. ventrale). In both cases, however, the dorsal side of the protruding structure seems to be equally and significantly reduced. As far as is known, the functional meaning of this remarkable difference remains obscure. Its taxonomic importance will be a matter for further studies, when more species of the genus are better characterized., Published as part of Pe��a-Santiago, R. & ��lvarez-Ortega, S., 2014, Re-description of three species of the genus Sectonema Thorne, 1930 (Nematoda: Dorylaimida: Aporcelaimidae) originally studied by E. Altherr, pp. 63-74 in Zootaxa 3881 (1) on pages 64-69, DOI: 10.11646/zootaxa.3881.1.5, http://zenodo.org/record/287404, {"references":["Altherr, E. (1965) La faune des sables submerges des rives du Rhin pres de Krefeld. Nematodes. Gewasser und Abwasser, Dusseldorf, 39 / 40, 80 - 101.","Thorne, G. (1930) Predaceous nemas of the genus Nygolaimus and a new genus Sectonema. Journal of Agricultural Research, USDA, 41, 445 - 466.","Andrassy, I. (1984) Ismet huszonot uj Nematoda faj a magyar faunaban. [Once again: twenty-five nematode species new to the Hungarian fauna]. Allattani Kozlemenyek, 71, 177 - 82. [in Hungarian, with an English summary]","Andrassy, I. (1990) Szabadon elo fonalfergek (Nematoda) a magyar faunaban. [Free-living nematoda in the Hungarian fauna]. Allattani Kozlemenyek, 76, 17 - 38. [in Hungarian, with an English summary]","Andrassy, I. (2009) Free-living nematodes of Hungary. III. Pedozoologica Hungarica nº 5. Hungarian Natural History Museum. Budapest, 608 pp. [Hungary]","de Man, J. G. (1921) Nouvelles recherches sur les nematodes libres terricoles de la Hollande. Capita Zoologica, 1, 3 - 62","Loof, P. A. A. (1961) On the identity of Dorylaimus robustus de Man. Nematologica, 6, 42 - 48. http: // dx. doi. org / 10.1163 / 187529261 x 00261","Heyns, J. (1965) On the morphology and taxonomy of the Aporcelaimidae, a new family of dorylaimoid nematodes. Entomology Memoirs, Department of Agricultural Technical Services, Republic of South Africa, 10, 1 - 51."]}

Sectonema heynsi Altherr, 1968 (Fig. 4) Material examined. Female holotype and one juvenile paratype, in poor general condition as the female is visibly flattened and broken in two parts, and some morphological features have become obscure. Measurements. See Table 1. Description. Female: Slender nematode of large size, 6.45 mm long. Body cylindrical, distinctly tapering towards the anterior end, less so towards the posterior one because the caudal region is rounded. Habitus regularly curved ventrad after fixation, C-shaped, Cuticle three-layered, especially distinct at caudal region, consisting of thin and smooth outer layer, a thicker inner layer bearing radial striation, and a thick inner layer; thickness 4 ��m at anterior region, 8 ��m in mid-body and 14 ��m on tail. Lateral chord 25 ��m wide at mid-body, occupying ca onesixth (? 16 %) of mid-body diameter. Body pores obscure. Lip region nearly truncate, offset by deep constriction, 3.6 times as wide as high and 18 % of body diameter at neck base; lips separate; labial and cephalic papillae distinct but low, weakly protruding; circumoral area bearing cilia- or small setae-like projections. Amphid fovea not observed since the anterior region is in ventral view. Cheilostom as long as wide. Mural tooth (as seen in ventral view) probably typical of the genus, i.e. lacking a distinct dorsal arm, ca three-fourths (70 %) of lip region diameter long or 0.31 % of body length, and somewhat extruded. Guiding ring weak, plicate. Odontophore linear, rod-like, its precise length difficult to establish. Pharynx distinctly muscular and tripartite, consisting of an anterior thickened spindle-shaped region running from the odontophore base to near the nerve ring, a narrower intermediate section enlarging very gradually, and a basal expansion 10.0 times as long as wide and 5.5 times as long as body diameter, and occupying 68 % of total neck length. Pharyngeal gland nuclei obscure. Cardia non-distinguishable. Genital system didelphic-amphidelphic, but only the anterior branch is observable, being 607 ��m long and occupying 9 % of total body length: ovary large, 303 ��m long; oviduct obscure; uterus apparently a simple but long tube 263 ��m or? 1.7 times the body diameter; vagina? 115 ��m long or? 74 % of body diameter, with pars refringens obscure; vulva (as seen in ventral view) a long transverse slit. Prerectum and rectum inconspicuous. Tail short and rounded to rounded conoid, slightly more convex at its dorsal side; caudal pores two pairs, subdorsal, at the middle of tail. Male: Unknown. Diagnosis (based on the holotype). Sectonema heynsi is characterized by its body 6.45 mm long, lip region offset by deep constriction and 28 ��m broad, circumoral area bearing cilia- or seta-like structures, mural tooth-like structure 20 ��m long, neck 1256 ��m long, pharyngeal expansion 856 ��m long or 68 % of total neck length, uterus a tube-like structure 263 ��m or? 1.7 times the corresponding body diameter, V = 50, tail short and rounded to conoid (54 ��m, c = 120, c��� = 0.7), and male unknown. Relationships. Leaving aside the presence of cilia- or seta-like structures covering the circumoral area, S. heynsi is morphometrically very similar to S. demani, another species described by Altherr. The nature of their mural tooth and vagina might be also different, but due the bad condition of the female holotype of S. heynsi, any further comparative analysis is impossible. (See also remarks below.) In having cilia- or seta-like structures covering the circumoral area, a very special feature for dorylaims, S. heynsi resembles S. barbatum Heyns, 1965, but it can be easily distinguished from this in its much larger general size (vs body length 3.89 mm). Type locality and habitat. Germany, Reichmannsdorf, Obere H��lle; collected on May 6 th, 1965. Other localities and habitats. Germany, Wildenspring (Altherr, 1974). Type material. Female holotype and one juvenile paratype on slide labelled NE 0 97 and 0 96, repectively, deposited with E. Altherr���s nematode collection at the Museo Cantonale di Storia Naturale���Lugano, Switzerland. Remarks. Sectonema heynsi and S. demani are very similar morphometrically, with no significant difference affecting their most relevant measurements and ratios. The presence of cilia- or seta-like structures covering the circumoral area, a feature originally reported by Altherr (1968) as well, is a remarkable diagnostic feature of S. heynsi and may be the reason why Altherr did not compare both species when describing S. heynsi in spite of their similarity. As mentioned above (see relationships), the morphology of the mural tooth and the vagina might be also different, but, because the female holotype of S. heynsi can only observed in subventral view, it is not possible to provide additional details. Altherr (1974) reported S. heynsi for the second time in the same geographical area, but he gave a very brief description of one female and one juvenile and did not add any new relevant information about the morphology of the species., Published as part of Pe��a-Santiago, R. & ��lvarez-Ortega, S., 2014, Re-description of three species of the genus Sectonema Thorne, 1930 (Nematoda: Dorylaimida: Aporcelaimidae) originally studied by E. Altherr, pp. 63-74 in Zootaxa 3881 (1) on page 70, DOI: 10.11646/zootaxa.3881.1.5, http://zenodo.org/record/287404, {"references":["Altherr, E. (1968) Nematodes de la nappe phreatique du reseau fluvial de la Saale (Thuringe) et psammiques du Lac Stechlin (Brandebourg du Nord). Limnologica, 6, 247 - 320.","Heyns, J. (1965) On the morphology and taxonomy of the Aporcelaimidae, a new family of dorylaimoid nematodes. Entomology Memoirs, Department of Agricultural Technical Services, Republic of South Africa, 10, 1 - 51.","Altherr, E. (1974) Nematodes de la nappe phreatique du reseau fluvial de la Saale (Thuringe), II. Limnologica, 9, 81 - 132."]}

Sectonema macrospiculum (Altherr, 1958) Heyns, 1965 (Fig. 5) Syn. Nygolaimus macrospiculum Altherr, 1958 Material examined. Female holotype, one male paratype and one juvenile paratype in acceptable state of preservation, but flattened. Measurements. See Table 1. Description. Adult: Slender nematodes of large size, 4.05, 5.06 mm long. Body cylindrical, distinctly tapering towards the posterior end, less so towards the anterior one because the caudal region is rounded conoid. Habitus somewhat sigmoid after fixation. Cuticle three-layered, especially obvious at caudal region, consisting of a thin outer layer bearing weak transverse striation, a thick intermediate layer bearing radial striation and fine criss-cross lines through the entire body, and thinner inner layer; thickness 4 ��m at anterior region, 3.5 ��m in mid-body and 7, 10 ��m on tail. Lateral chord 16, 19 ��m wide at mid-body, occupying about one-seventh (14, 13%) of mid-body diameter. Body pores distinct, two dorsal and two ventral pores at cervical region behind the level of odontophore base; fine ventral pores also visible throughout the entire body. Lip region offset by constriction, 3.6 times as wide as high and 25, 20% of body diameter at neck base; lips separate, with labial and cephalic papillae distinct but low, weakly protruding. Amphid fovea cup- to stirrup-shaped, opening at level of the cephalic constriction and occupying 14 ��m or about one-half (49, 52%) of lip region diameter. Cheilostom nearly cylindrical, lacking any differentiation. Stomatal protruding structure an odontostyle similar to that found in S. ventrale (see recent redescription by Pe��a-Santiago & ��lvarez-Ortega, in press): ventral side 0.5 times as long as lip region diameter or 0.36, 0.29 % of body length, and 3.7, 3.3 times as long as its width at the base; dorsal side with very long aperture showing a weak but perceptible concavity at its posterior part, and a very short refractive terminal part apparently joining the dorsal wall of the stoma. Guiding ring weak, plicate, situated at 14, 13 ��m or 0.49 times the lip region diameter from the anterior end. Odontophore linear, rod-like, 2.0, 2.2 times the mural tooth length. Anterior region of the pharynx slender but distinctly muscular, enlarging very gradually; basal expansion 8.8, 10.0 times as long as wide, 5.0, 4.7 times as long as body diameter, and occupying 67, 68% of total neck length. Pharyngeal gland nuclei obscure. Nerve ring located at 194, 215 ��m from anterior end or 24, 23% of total neck length. Cardia rounded conoid, 28 x 23, 27 ��m; a weak ring-like structure is present surrounding its junction to pharyngeal base. Intestine containing setae as result of the digestion of oligochaete prey. Female: Genital system didelphic-amphidelphic, with both branches almost equally and well developed, the anterior 562 ��m long or 11 % of body length and the posterior 585 ��m long or 12 % of body length. Ovaries large, usually surpassing the sphincter level, the anterior 294 ��m, the posterior 305 ��m long, with oocytes arranged first in two or more rows, then in a single row. Oviduct 237���240 ��m long or 1.6���1.7 times the corresponding body diameter, and consisting of a slender part with prismatic cells and a well developed pars dilatata. Oviduct-uterus junction marked by a sphincter. Uterus a simple tube-like structure, 270���297 ��m long or 1.9���2.1 times the corresponding body diameter; vagina extending inwards 77 ��m or 54 % of body diameter: pars proximalis 59 x 33 ��m, with somewhat sigmoid walls and surrounded by moderately developed, circular musculature; pars refringens with two trapezoidal pieces measuring 15 x 10.5 ��m and a combined width of 31 ��m; and pars distalis short, 6 ��m long. Vulva a slightly post-equatorial transverse slit. Prerectum 2.1, rectum 0.8 anal body diameters long. Tail short, convex conoid; caudal pores not well perceptible. Male: General morphology similar to that of females. Genital system diorchic, with opposite testes. In addition to the ad-cloacal pair, situated at about 21 ��m from the cloacal aperture, there is a series of eight irregularly spaced, 12���17 ��m apart, ventromedian supplements, the posteriormost of which is located at 79 ��m from the ad-cloacal pair, out the range of spicules. Spicules very robust and massive especially at its posterior half, 2.8 times as long as wide, and 1.4 times as long as cloacal body diameters; dorsal side regularly convex, ventral one very weakly concave, lacking distinct hump and hollow; curvature 127 ��; head very short, occupying 7 % of spicule total length, its dorsal side weakly curved and longer than the ventral one, which is extremely short; median piece 4.1 times as long as wide, occupying 60 % of spicule maximum width, reaching the terminal tip; posterior end 13 ��m wide. Lateral guiding piece 25 ��m long, 5.0 times as long as wide. Prerectum obscure, cloaca hardly longer (1.1 times) than the corresponding body width long. Tail more conoid than that of female, but with the ventral side visibly more straight; caudal pores obscure. Juvenile: General morphology similar to that of adults. Both the functional and the substitution odontostyle equally developed and 14 ��m long. Diagnosis. Sectonema macrospiculum is characterized by its 4.07���5.06 mm long and slender (a = 35���37) body, lip region offset by deep constriction and 27���28 ��m broad, ventral side of odontostyle 15 ��m long, neck 823���935 ��m long, pharyngeal expansion 555���640 ��m long or 67���68 % of total neck length, uterus a simple tube-like structure 270���297 ��m long or 1.9���2.1 times the corresponding body diameter, pars refringens vaginae with two well developed sclerotized pieces, V = 53, female tail short and convex conoid with rounded terminus (62 ��m, c = 82, c��� = 0.7), male tail more conoid thant that of female and with the ventral side visibly more straight (58 ��m, c = 71, c��� = 0.8), spicules 107 ��m long, and eight irregularly spaced ventromedian supplements bearing hiatus. Relationships. Sectonema macrospiculum is very similar to S. pseudoventrale Heyns, 1965 and S. ventrale. It differs from S. pseudoventrale in its wider lip region (vs 22���23 ��m wide), larger odontostyle (vs 9 ��m long), longer uterus (vs about 123 ��m or 1.3 times the body diameter), and longer spicules (vs 90���95 ��m). It can be distinguished from S. ventrale in its smaller general size (vs body 7.09���10.42 mm long), caudal region relatively longer (vs c > 100), and longer spicules (vs 120 ��m). Type material. Female holotype and one male and one juveniles paratypes on slide labelled NE 0 0 9, deposited with E. Altherr���s nematode collection at the Museo Cantonale di Storia Naturale���Lugano, Switzerland. Distribution. This species is only known to occur in its type locality in Germany, near Deichhausen, Germany, where it was collected from seepage water in the banks of the Weser River. Remarks. The above description perfectly fits the original one as well the re-description (based on type specimens) provided by Heyns (1965), although new morphological details are herein given, especially those regarding the odontostyle and the genital system of both the female and the male., Published as part of Pe��a-Santiago, R. & ��lvarez-Ortega, S., 2014, Re-description of three species of the genus Sectonema Thorne, 1930 (Nematoda: Dorylaimida: Aporcelaimidae) originally studied by E. Altherr, pp. 63-74 in Zootaxa 3881 (1) on pages 71-72, DOI: 10.11646/zootaxa.3881.1.5, http://zenodo.org/record/287404, {"references":["Altherr, E. (1958) Nematodes du bassin inferieur de la Weser et des dunes d'Heligoland: especes nouvelles ou incompletement decrites. Memoires de la Societe vaudoise des sciences naturelles, 12, 45 - 63.","Heyns, J. (1965) On the morphology and taxonomy of the Aporcelaimidae, a new family of dorylaimoid nematodes. Entomology Memoirs, Department of Agricultural Technical Services, Republic of South Africa, 10, 1 - 51."]}

Metaxonchium persicum sp. n. (Figs 1–4) Morphometrics. See Table 1. Description. Type population from Azarbaijan rangelands (6 ♀♀ + 3 ♂♂). Adult: Slender to very slender nematodes of medium to large size, 2.46–3.12 mm long. Body cylindrical, visibly tapering towards the anterior end, less so towards the posterior end since the caudal region is short and conoid. Habitus curved ventrad upon fixation, C- or G-shaped. Cuticle three-layered, consisting of inner layer thicker than the others, especially obvious at caudal region where it bears distinct radial striation, an intermediate and more transparent layer, and a thinner outer layer nearly smooth under LM but bearing very fine transverse striation under SEM; cuticle thickness 2–3 Μm in anterior region, 4–6 Μm at mid-body and 8–15 Μm on dorsal side of tail. Cervical lacunae often clearly visible. Lateral chord comparatively narrow, 5–7 Μm wide or up to one-tenth (7–10 %) of mid-body diameter, of granular nature and lacking any other differentiation. Lip region rounded to slightly truncate anteriorly, offset by constriction, 2.2–2.8 times as broad as high or less than one-sixth (11–15 %) of body diameter at neck base; lips separate, under SEM appearing conoid, tapering toward the oral aperture, and with deep radial incisures in between; labial and cephalic papillae very low, not interfering the labial contour. Amphid fovea cup-like, its aperture 7–9 µm wide or occupying about four-fifths (75–82 %) of lip region diameter. Cheilostom a truncate cone, lacking any differentiation. Odontostyle small, somewhat fusiform, as thick as the cuticle at its level, equal to or hardly longer (1.0– 1.2 times) than lip region diameter, 5.8–6.8 times as long as wide and 0.36–0.40 % of body length; aperture 3.0– 3.5 µm long, occupying one-fourth to one-third (25–35 %) of total length. Guiding ring thin, simple but visibly refractive, at 11–14 µm or 0.8–0.9 times the lip region diameter from the anterior end. Odontophore rod-like, 1.8–2.2 times the odontostyle length, bearing a very slight thickening at its approximate midpoint. Pharynx consisting of a slender and weakly muscular anterior portion, which is separated from the basal expansion by a short isthmus-like narrowing, and bearing a well developed, spindle-shaped thickening with valvelike structures, situated at 117–155 Μm from anterior end; basal expansion 13–20 times as long as broad, 7.5–9.9 times longer than body diameter at neck base, and occupying up to three-fourths (68–73 %) of total neck length; a very distinct spiral muscular sheath, with nearly straight muscular bands, envelops the whole basal expansion. Cardia tongue-like, 22–25 Μm long x 13–14 Μm wide, surrounded by intestinal tissue. Caudal region conoid with broadly rounded terminus, ventrally straighter, dorsally more convex; caudal pores two pairs at the posterior half of tail, one lateral, another subdorsal. Female: Genital system monodelphic-opisthodelphic. Anterior branch 117–324 Μm long or 6–11 % of body length, and consisting of a long uterine sac often devoid of sperm cells, and a small solid terminal mass probably representing oviduct and/or ovary remnants. Posterior branch very long and impossible to measure as its tract always appears strongly convoluted: reflexed ovary large, 170–370 µm long, with oocytes arranged first in several rows and then in a single row; oviduct joining the ovary subterminally, 135–142 Μm long or 1.4–2.1 body diameters, and consisting of a tubular part made of prismatic cells and a well developed pars dilatata with distinct lumen and occasionally containing sperm cells. A strong sphincter separates oviduct and uterus. Uterus very long and tripartite, i.e., provided with a proximal region with very wide lumen, a convoluted long intermediate region with narrow lumen and containing numerous refractive, irregular elements (apophyses), and a large spherical distal pars dilatata. One female bearing a uterine egg, 145 x 52 µm. Vagina 32–42 µm long, extending inwards about one-half (43–55 %) of the corresponding body diameter; pars proximalis longer than wide, 21–24 x 15 –20 Μm, with convergent walls and surrounded by moderately developed, circular musculature; pars refringens (in lateral view) consisting of two trapezoidal pieces measuring 4– 5 x 7–8 µm and with a combined width of 9–11 µm; pars distalis 3–7 Μm long. Vulva a somewhat posterior transverse slit, about 10 µm long. Prerectum 4–10, rectum 1.0– 1.4 anal body diameters long. Anus a straight transverse slit about 8 µm long. Male: Genital system diorchic, with opposite testes. In addition to the adcloacal pair, situated at 15–17 Μm from cloacal aperture, there is a series of 7–10 ventromedian supplements 17–34 Μm apart, the posteriormost of which is situated at 38–50 Μm from the adcloacal pair; hiatus lacking as at least two ventromedian supplements lie within the range of spicules. Spicules dorylaimoid, curved ventrad, relatively slender (7.8–8.3 times as long as wide) and long (1.8–2.2 times the cloacal body diameter), and with a rather narrow anterior part. Lateral guiding pieces 19–20 Μm long, 9–10 six times as long as wide. Other material examined (9 ♀♀ from three locations). These nine females are nearly identical to those of type population. They have slightly smaller general size, but largely overlap in their morphometric ranges. In many of these females the pars refringens vaginae is variably developed, often with weaker sclerotization than usual. It is also remarkable that no male has been collected together with the females and that these do not contain sperm cells. Diagnosis. The new species is characterized by its 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 threefourths 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 a 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 93–102 µm long and 7–10 spaced ventromedian supplements, at least two of them within the range of spicules. Relationships. In having comparatively large general size (body length more than 2 mm), echinophorous uterus (i.e., bearing abundant, refractive, spine-like elements or apophyses) and posterior vulva position (V more than 50), the new species is very similar to M. bihariense (Popovici, 1990) Andrássy, 1996, M. giennense Peña- Santiago & Coomans, 1990 and M. paravalvulatum Peña-Santiago & Coomans, 1990. It differs from M. bihariense in its wider lip region (8–11 vs 7–8 µm, n= 14 in Romanian material), longer neck (773–1000 vs 600–775 µm; b = 2.8–3.4 vs b = 3.2 –4.0), presence of a valvate swelling at the anterior section of pharynx (vs absent or overlooked), an isthmus-like narrowing separating both pharyngeal sections (vs apparently no special differentiation marking this separation), pars refringens vaginae readily perceptible (vs weakly sclerotized if present), and male known (vs unknown). From M. giennense in the presence (vs absence) of valves at the spindle-shaped swelling in the anterior slender portion of pharynx, larger spicules (93–102 vs 71–87 µm long, n= 9), and lower number of ventromedian supplements (7–10 vs 10–14) with different arrangement (two vs at least three of them within the spicules range, with the last two somewhat shifted from the midventral position, one on the left, the other on the right in M. giennense). And from M. paravalvulatum in its longer male tail (37–43 vs 30 µm), larger spicules (93–102 vs 71 µm long) with different shape (more slender and having a long slender anterior part vs more robust and lacking an especially narrow anterior part), and lower number of ventromedian supplements (7–10 vs 11) with different arrangement (two vs only one distinctly lying within the range of spicules). Type locality and habitat. The new species was collected from northwest Iran, Mahmood Abad region, East Azarbaijan province (GPS coordinates: N 38 ° 48 ′ 43.5 E 46 ° 51 59.6 ″), in Arasbaran rangelands, during 2012. Other localities and habitats. Dolat Abad district, Marand, in an orchard with fruit trees; Ass district, Arasbaran, in a natural pasture; and Hervi district, around Tabriz, in an orchard with fruit trees. Type material. Female holotype, two female and two male paratypes deposited in the Collection of Nematology Lab., University of Tabriz, Tabriz, Iran. Two female and one male paratypes deposited in the Nematode Collection of the University of Jaén, Spain. Etymology. The specific epithet refers to the geographical origin of this species in Persia, the former name of Iran. Remarks. Metaxonchium persicum sp. n. is morphometrically very similar to M. giennense and M. paravalvulatum, making the identification of their respective females especially problematic. Nevertheless, the morphology of the spicules and the number and arrangement of the ventromedian supplements seem to be sufficiently different to support a provisionally separate status for these three species. Holotype Paratypes Character n ♀ 5 ♀♀ 3 ♂♂ 4 ♀♀ 4 ♀♀ ♀ 15 ♀&female

Peña-Santiago, R., Álvarez-Ortega, S. (2014): Re-description of three species of the genus Sectonema Thorne, 1930 (Nematoda: Dorylaimida: Aporcelaimidae) originally studied by E. Altherr. Zootaxa 3881 (1): 63-74, DOI: http://dx.doi.org/10.11646/zootaxa.3881.1.5

Vu, Tam T., Ciobanu, M., Abolafia, J., Peña-Santiago, R. (2010): Two remarkable new species of the genus Crassolabium Yeates, 1967 from Vietnam (Nematoda: Dorylaimida: Qudsianematidae). Journal of Natural History 44 (33-34): 2049-2064, DOI: 10.1080/00222933.2010.481055, URL: http://dx.doi.org/10.1080/00222933.2010.481055

This contribution provides a compilation of tylenchid species hitherto reported from the Iberian Peninsula and the Balearic Island A total of 339 species belonging to 67 general and 17 families form provisionally the Iberian fauna.

The type species of the genus Epacrolaimus, Epacrolaimus declinatoaculeatus, is studied from the re-examination of type material of Aporcelaimus vorax, its junior synonym, and the observation of several Iberian populations and a few Iranian specimens. Morphologically, it displays a recognizable morphological pattern characterized by, among other features, the incurved nature of its odontostyle aperture, presence of perioral liplets or lobes, lip region 24-31 μm wide, odontostyle 21-25 μm long and comparatively anterior location of S2N pharyngeal gland nuclei. Nevertheless, variations in some morphological traits (vagina shape and tail shape) and in several morphometrics (body length, uterus length, vulva position, tail length and spicule length) are also noted. Sequences of D2-D3 domains of the 28S rDNA, 18S rDNA and COI mtDNA were obtained from several Iberian populations. Their analyses, in particular those from D2-D3 sequences, revealed the existence of a highly supported clade ((Epacrolaimus + Sectonema) + Metaporcelaimus), with a closer relationship between Epacrolaimus and Palaearctic populations of Sectonema, whereas the remaining aporcelaimid genera occupied placements in other clades. These results are discussed, with especial emphasis on the intricate separation of Epacrolaimus and Sectonema, which display significantly different protruding stomatal structure in spite of their close evolutionary relationship as derived from molecular trees., This work was support by the University of Jaén, Spain, through the research program ‘PAIUJA 20121/2022: EI_RNM02_2021’.