identifier	taxonID	type	CVterm	format	language	title	description	additionalInformationURL	UsageTerms	rights	Owner	contributor	creator	bibliographicCitation
715CB0A23A4B561380DD6D06692FC455.text	715CB0A23A4B561380DD6D06692FC455.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Stenasellus angiangensis Marin, Palatov, Thinh, Douady & Malard 2026	<div><p>Stenasellus angiangensis Marin, Palatov, Thinh, Douady &amp; Malard sp. nov.</p><p>Figs 6 b – d, 11</p><p>Material examined.</p><p>Holotype: • ♂, bl. 5.1 mm, ZMMU Mc-1471 – Vietnam, An Giang Province, <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=104.91303&amp;materialsCitation.latitude=10.484917" title="Search Plazi for locations around (long 104.91303/lat 10.484917)">Tri Tôn</a>, 10°29'05.7"N, 104°54'46.9"E, in hyporheic habitats of a small mountainous river, located on a mountainside overgrown with forest (site number and code: 9, ANGIANG 1), hand net sampling, coll. D. Palatov &amp; I. Marin, 10 November 2023 ; Paratype, ♀, bl. 4.7 mm, ZMMU Mc-1472 – same locality and date as for holotype .</p><p>Paratypes: • 1 ♂, 1 ♀ (ZMMU Mc-1473), 1 ♂, 1 ♀ (LEMMI, used for SEM), 1 ♂, 2 ♀♀ (including 1 posterior part of a female) (UCBLZ: Coll Number 2012.11.25.88) – Vietnam, An Giang Province, <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=105.005585&amp;materialsCitation.latitude=10.496612" title="Search Plazi for locations around (long 105.005585/lat 10.496612)">Tri Tôn</a>, 10°29'47.8"N, 105°00'20.1"E, in hyporheic habitats of a small mountainous river, located on a mountainside overgrown with forest (11, ANGIANG 2), hand net sampling, coll. D. Palatov &amp; I. Marin, 10 November 2023 .</p><p>Additional material.</p><p>Vietnam • 3 ♀♀, 2 ♂♂ (LEMMI), 1 ♀, 1 head of specimen (UCBLZ: Coll Number 2012.11.25.87) – An Giang Province, <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=104.91303&amp;materialsCitation.latitude=10.484917" title="Search Plazi for locations around (long 104.91303/lat 10.484917)">Tri Tôn</a>, 10°29'05.7"N, 104°54'46.9"E, in hyporheic habitats of a small mountainous river, located on a mountainside overgrown with forest (9, ANGIANG 1), hand net sampling, coll. D. Palatov &amp; I. Marin, 11 September 2023 ; • 2 ♀♀ (LEMMI), 1 ♀, 2 ♂♂ (UCBLZ: Coll Number 2012.11.25.89) – 10°29'00.1"N, 104°59'09.6"E, in hyporheic habitats of a small mountainous river, located on a mountainside overgrown with forest (10, ANGIANG 3), hand net sampling, coll. D. Palatov &amp; I. Marin, 11 November 2023 .</p><p>Etymology.</p><p>The species name, angiangensis, is given after An Giang Province of southern Vietnam, where the species was discovered.</p><p>Diagnosis.</p><p>Body dorsal surface smooth, with small scattered marginal setae. Antennula and antenna relatively short, with 8 and 26 flagellar articles, respectively. Disto-mesial margin of endite of maxilliped with 2 coupling hooks. Male pleopod I with protopod without coupling hook on inner margin. Distal end of exopod of male pleopod I bluntly convex. Male pleopod II with almost quadrate protopod with convex external margin; exopod with small and subquadrate proximal article with one small seta on external margin; distal article of exopod oval with 6 simple setae along external margin. Endopod of male pleopod II with distal article subequal to basal article, without spines or setae; terminal end of the distal article of endopod bearing a flute-shaped efferent canal and a strong spur, the terminal end of which reaches the terminal end of the efferent canal. Endopod of pleopods III, IV, and V deeply bifurcated.</p><p>Description.</p><p>Holotype ♂ (ZMMU Mc-1471). Body elongated, about 6.0 × longer than wide (Fig. 6 b). Head trapezoidal, about 1.2 × wider than long, with straight frontal margin, dorsal surface smooth, with small marginal setae. Pereonite I about 2.2 × wider than long, shorter that pereonites II – IV; pereonites II – IV subequal in length, about 2.3–2.5 × wider than long, with rounded lateral margins; pereonites V – VII subequal in length, about 1.5–2.2 × wider than long, slightly longer than pereonites II – IV, with posterolateral margins projected posteriorly. Pleonites I – II (Fig. 10 a) subequal in length, about 2.8–3.0 × wider than long, with projected posterolateral corner, furnished with strong blunt spines and simple setae.</p><p>Coloration. Characteristic for other known congeneric species; deeply pink or red (see Fig. 6 b – d).</p><p>Body size. The average body length differed significantly between males and females: males averaged 4.43 ± 0.21 mm (min: 4.23; max: 4.80; n = 7), while females averaged 4.87 ± 0.46 mm (min: 4.15; max: 6.00; n = 7). Similarly, the average body width also showed a significant difference, with males measuring 0.81 ± 0.01 mm (min: 0.80; max: 0.82; n = 6) and females 0.88 ± 0.07 mm (min: 0.80; max: 1.10; n = 12). In both cases, the differences were statistically significant (p &lt;0.05). These results indicate that females are significantly larger than males in terms of both body length and body width. Body is 5.4 ± 0.2 × longer than wide (n = 18 specimens), with no difference between males and females.</p><p>Antennula (Fig. 7 a, b) relatively short, reaching pereonite II, slightly longer than the peduncle of antenna; peduncle 4 - articulated, article I stout, about 1.2 × longer than wide, with 4 strong setae on distal margin, article II about 1.8 × longer than wide, with strong simple and several plumose setae, article III about 1.7 × longer than wide, with 2 distal glabrous and 1 long plumose setae, article IV short, about as long as wide, with 1 plumose setae; flagellum with 8 articles, five distal articles bearing a single aesthetasc.</p><p>Antenna (Fig. 7 c) with 6 - articulated peduncles; articles I – II reduced, article II about 2.0 × wider than long; articles III – V relatively stout, slightly increasing in length, with length proportion articles III – VI close to 1.0 / 0.8 / 1.2 / 1.8; article III about 1.5 × longer than wide, armed with long simple setae distally; article IV about 1.6 × longer than wide, with minute squama bearing stout setae, article V about 2.3 × longer than wide, armed with several stout and numerous simple setae, article VI about 4.2 × longer than wide, covered with simple setae; flagellum about 1.8 × longer than peduncle, reaching to pereonite IV, with 26 articles.</p><p>Labrum (upper lip) (Fig. 7 d) oval, apical margin convex, with numerous small fine setae.</p><p>Labium (lower lip) (Fig. 7 e) with feebly developed inner lobes.</p><p>Mandibles. Right mandible (Fig. 8 a, b) with incisor process bearing 4 teeth and sclerotized lama, lacinia mobilis strong and stout, with 5 blunt teeth; molar process with 12 long setae. Left mandible (Fig. 8 c, d) with incisor process bearing 3 teeth and sclerotized lama, lacinia mobilis feebly developed; molar process with 12 long setae. Mandibular palp (Fig. 8 a, c) 3 - articulated, basal article I with 1 long seta on distal corner, article II with 7–8 setae on internal margin, and terminal article III with almost 10 setae situated in two rows and 2 long distal simple setae.</p><p>Maxillula (Fig. 8 e) with 13 distally curved pectinate robust setae in two rows on outer lobe (Fig. 8 f); with 2 strong scarcely plumose robust combs and 1–2 curved pectinate simple setae on inner lobe.</p><p>Maxilla (Fig. 8 g) lateral and middle endites each with 8 curved pectinate robust setae; mesial endite with 11 long robust plumose combs and several slender simple setae.</p><p>Maxilliped (Fig. 8 h) with disto-mesial margin of endite bearing 2 coupling hooks and numerous robust setae of different length; palp 4 - articulated, with articles armed with numerous long simple setae along inferior margins.</p><p>Pereopod I (Fig. 9 a) haptorial, with robust dactylar ventral claw; coxa about as long as wide, with 3 long marginal setae; basis about 2.0 × longer than wide, with inner margin distinctly concave proximally; ischium about 1.4 × longer than wide, with 1 strong medial seta on external margin; merus with supradistal angle bearing 1 strong seta, inner margin distally with 2 short robust and several simple setae; carpus triangular, inferior margin covered with numerous long and short robust setae and several simple setae; propodus about 2.1 × as long as wide, somewhat teardrop-shaped, inferior margin covered with several robust and serrated setae; dactylus 4.8 × as long as basal width, inferior margin with row of contiguous scale-like flattened setae with accessory setulae, main unguis elongate, distally sharpening.</p><p>Pereopod II (Fig. 9 c) with coxa about as long as wide, with tiny marginal setae; basis about 2.0 × longer than maximal width, swollen in central part, with external margin distinctly convex, armed with 4 strong setae proximally, inner margin with small median setae; ischium about 1.7 × longer than wide, with external margin armed with 3 long robust medial and 3 subdistal short setae; merus about as long as wide, subtriangular in shape, with supradistal angle bearing 3 strong setae, inner margin distally with 2 short robust and several simple setae; carpus subcylindrical, about 2.5 × longer than wide, widening proximally, inferior margin covered with numerous long and short robust setae and several simple setae; propodus about 4.8 × as long as wide, inferior margin covered with several robust and serrated setae; dactylus shorter than main unguis, with single long accessory spine on sternal margin.</p><p>Pereopods III – VII (Fig. 9 d – h) generally similar in shape with pereopod II; pereopod length progressively increasing from pereopods II to VII; coxa about as long as wide, with tiny marginal setae; basis about 2.2 × longer than maximal width in PIII – PIV and about 1.6 × - 1.7 × in PV – PVII, swollen in central part, with external margin distinctly convex, armed with 3 strong setae proximally, inner margin with small median setae; ischium about 1.6 × in PIII and about 1.9 × - 2.1 × in PIV – PVII, longer than wide, external margin armed with 3 long robust medial and 3 subdistal short setae in PIII and PIV, with 5 long robust medial setae in PV – PVII; merus about as long as wide, subtriangular in shape, with supradistal angle bearing 3 strong long setae and inner margin distally with 3 short robust and several simple setae in PIII – PIV and supradistal angle with 5 strong long setae, inner margin distally with 3–4 short robust and several simple setae in PV – PVII; carpus subcylindrical, about 2.7 × – 3.0 × longer than wide, widening proximally, inferior margin covered with numerous long and short robust setae and several simple setae in PIII – PV and inferior margin covered with 2 long median and 2 subdistal robust setae accompanying with several simple setae in PVI and PVII; propodus about 4.8 × – 5.2 × as long as wide, inferior margin covered with several robust and serrated setae; dactylus shorter than main unguis, with single long accessory spine on sternal margin.</p><p>Pleotelson elongated, about 1.5 × longer than broad, with scattered marginal setae; posterior margin with two slight excavations extended in the center, bluntly rounded (Fig. 10 b).</p><p>Pleopod I (Fig. 10 d) with protopod about as long as wide, without coupling hook on inner margin; exopod elongated, bluntly rounded distally, shovel-like, mesial margin with a row of 12 simple setae, apical margin with several tiny setae, lateral margin convex.</p><p>Pleopod II (Fig. 10 e) almost quadrate protopod about as long as wide, external margin convex, with one paramedial spine; exopod with small and subquadrate proximal article, with small seta on external margin, distal article oval, about as long as wide, with 6 simple setae along external margin; endopod (Fig. 10 f) with slender articles, distal article subequal to basal article, without spines or setae. Terminal end of the distal article of endodpod bearing a flute-shaped efferent canal and a strong spur, the terminal end of which reaches the terminal end of the efferent canal.</p><p>Pleopod III (Fig. 10 g) with endopod 0.8 × as long as exopod, deeply bifurcated distally; exopod about 2.5 × as long as wide, with distinct transverse suture, apical margin bluntly convex, with several slender simple setae. Pleopod IV (Fig. 10 h) with endopod slightly longer than exopod, deeply bifurcated distally; exopod about 2.2 × as long as wide, with transverse suture, distolateral margin with 17 slender simple setae. Pleopod V (Fig. 10 i) similar to pleopods III – IV, endopod subequal in length to exopod, deeply bifurcated distally; exopod about 2.4 × as long as wide, with transverse suture, distolateral margin with numerous tiny setae.</p><p>Uropods (Fig. 10 j) as long as pleotelson, protopod about 1.5 × longer than wide, covered with strong spines; endopod longer than exopod, endopod about 9.0 × as long as wide, covered with long distal glabrous setae; exopod about 7.7 × as long as wide, covered with long distal glabrous setae.</p><p>Penial processes (Fig. 10 k) elongated, cylindrical, sharping distally, about 3.8 × longer than greatest width.</p><p>Females. Pleotelson and antenna are subequal to those in ♂♂. Pereopod I (Fig. 9 b) haptorial, with ventral claw, generally similar but with articles slightly slender than in ♂♂. Pleopod II (Fig. 10 c) with protopod triangular in shape, about as long as wide, with several simple setae along inner margin.</p><p>Taxonomic remarks.</p><p>Morphologically, the new species is most closely similar to Stenasellus cambodianus Boutin &amp; Magniez, 1985, which records are also most close geographically, being known from a cave of the Kampong Trach karst in southeastern Cambodia (see Boutin and Magniez 1985) and the cave Hang Gi ếng Tiên of the Hòn Chông karst in Kiên Giang Province of southern Vietnam (Deharveng et al. 2023). Both species share a strong spur on the segment of endopod of pleopod II in males, which makes it possible to separate them from other representatives of the genus Stenasellus . However, Stenasellus angiangensis sp. nov. is easily distinguishable from S. cambodianus and other species of Stenasellus due to the flute-shaped terminal end of the efferent canal (copulatory organ, see Fig. 10 f). As most species in Asia (Magniez 2005), endopods of pleopods III, IV and V are bifurcated in the new species, even deeply than in S. cambodianus (see Boutin and Magniez 1985). Indeed, all Stenasellus from Asia have bifurcated endopods III, IV and V except Stenasellus asiaticus Birstein &amp; Starostin, 1949 (Turkmenistan), Stenasellus boutini Magniez, 1991 (Cambodia), and three species from Thailand ( Stenasellus deharvengi Magniez, 1991, Stenasellus rigali Magniez, 1991 and Stenasellus mongnatei Magniez &amp; Panitvong, 2005).</p><p>Habitats and ecology.</p><p>All specimens of S. angiangensis sp. nov. were found in springs or hyporheic habitats along the banks of small mountainous rivers, located on forested slopes (see Fig. 6 a). These crustaceans appear to inhabit the lower river substrate layer composed of pebbles and sand, where moisture is retained even during the prolonged dry season with no rain (lasting 3–4 months). No specimens were found in cryptic microhabitats such as beneath large rocks or within the main river channel, suggesting a preference for stable, humid interstitial environments near stream banks.</p><p>Distribution.</p><p>The species is known only from the isolated mountainous massifs (free-standing hills), located in the western part of An Giang Province, which is part of the Mekong River Delta region in southern Vietnam.</p><p>ZooBank taxon ID.</p><p>The electronic version of this article in Portable Document Format will represent a published work according to the International Commission on Zoological Nomenclature (ICZN), and hence the new names contained in the electronic version are effectively published under that Code from the electronic edition alone. This published work and the nomenclatural acts it contains have been registered in ZooBank, the online registration system for the ICZN. The ZooBank Life Science Identifiers (LSID) for this publication is: https://zoobank.org/ 8F6D2242-2FE4-49A4-949C-56A75C39DA 6F. The online version of this work is archived and available from the following digital repositories: ZooKeys, PubMed Central and CLOCKSS. The LSID for the new species, Stenasellus angiangensis Marin, Palatov, Thinh, Douady &amp; Malard, sp. nov., is https://zoobank.org/ 997DB87C-7A52-4B3C-932F-BDCD2760A306.</p></div>	https://treatment.plazi.org/id/715CB0A23A4B561380DD6D06692FC455	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Pensoft via Plazi	Marin, Ivan N.;Palatov, Dmitry M.;Văn Thinh, Nguy ễn;Deharveng, Louis;Konecny-Dupré, Lara;Douady, Christophe J.;Malard, Florian	Marin, Ivan N., Palatov, Dmitry M., Văn Thinh, Nguy ễn, Deharveng, Louis, Konecny-Dupré, Lara, Douady, Christophe J., Malard, Florian (2026): An updated phylogeny of the family Stenasellidae (Crustacea, Isopoda), with a new species of Stenasellus from southern Vietnam. Subterranean Biology 55: 187-215, DOI: 10.3897/subtbiol.55.185185
