identifier	taxonID	type	CVterm	format	language	title	description	additionalInformationURL	UsageTerms	rights	Owner	contributor	creator	bibliographicCitation
03BD1C70FFA32910FEE6FAB99904C457.text	03BD1C70FFA32910FEE6FAB99904C457.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Sewellia Hora 1932	<div><p>Sewellia Hora, 1932</p><p>The genus Sewellia is diagnosed by a series of features apparently unique: the pelvic valve, the fan-shaped rostral barbels, and the duct between the fossa behind anterior rostral barbel and the oral cavity.</p><p>In Sewellia, the two pairs of rostral barbels appear as a kind of plate or flap, compressed, with a posterior fringe of 4–7 digitations, each ending in a conical papilla; additional papillae may be present on the barbel and small tubercles at the base (Fig. 1). The anterior barbel posteriorly touches the upper lip, or is fused at the base of the upper lip. The posterior barbel has the lateral part of the flap free, and the medial part is fused with the upper lip. There is one fossa behind each barbel. The posterior extremity of the anterior fossa is continued by a duct, whose entrance is apparently closed by a sphincter; when the duct is open, a needle inserted in the duct reaches without obstacle until about the level of the base of the anterior ray of the pectoral fin (Fig. 1). In some species (e.g., S. lineolata) the anterior barbel apparently covers the whole anterior fossa and possibly functions as a valve. All these structures are already present in the smallest examined specimens of S. lineolata (CMK 16676, 27.9 mm SL), S. diardi (CMK 22308, 19.6 mm SL), S. pudens (CMK 22380, 20.9 mm SL) and S. speciosa (CMK 22279, 17.2 mm SL). But in S. elongata, the largest of the available species, in the smallest specimens (e.g., CMK 15529, 15.1 mm SL; Fig. 2a), the rostral barbels are still cylindrical, but they already connect the rostral cap and the upper lip. The outer rostral barbel starts to have the diagnostic flat and digitate shape around 20 mm SL (Fig. 2b). Noteworthy is also that in small juveniles (up to about 23 mm SL), the gill opening extends downwards until shortly above the anterior pectoral-fin rays (Fig. 2c).</p><p>The upper lip is thin, smooth or covered by tiny papillae. The upper jaw is covered by a sheath, itself covered by unculi (K. W. Conway, pers. comm.). The lower lip is missing. Behind the middle of the lower jaw, is a thick ‘mental pad’ with or without papillae; this has sometimes been called lower lip in Balitoridae and Gastromyzontidae; I retain ‘mental pad’, following Roberts (1982a: 515, fig. 15). I had called ‘mental lobe’ a possibly homologous structure in Barbuccidae (Kottelat, 2025) .</p><p>In two species ( S. pterolineata, S. marmorata) there is a post-oral pouch behind the mouth (Fig. 3). The mouth is located in a depression, margined posteriorly by a postoral pouch. This is a skin fold extending across the ventral surface of the head, behind the mouth, covering the posterior part of the cavity or even the mandibular barbel and part of the posterior fossa. This leaves a pouch opening forward and extending backwards until about the level of the basis of pectoral-fin rays 1 to 3. The duct at the posterior extremity of the anterior fossa extends at least to the posterior margin of the pouch. The ventral surface of the rostral cap is covered by large tubercles.</p><p>Hora (1932: 315, 327) already hypothesised that the fossa could be connected with the mouth cavity. When adpressed on a flat structure, the pectoral and pelvic fins, the oro-pectoral fold, the posterior rostral barbel, and the upper lip form a tight sucker, opening posteriorly through the pelvic valve (Roberts, 1998: 273) and enclosing the mouth. It might be speculated that the anterior fossa and the duct allow the passage of waters to the gills when the sucker is closed. A video (Conway, 2022) shows the high frequency of mouth, gill opening, and pectoral fin movements.</p><p>Roberts (1998: 272) mentions an ‘oro-pectoral membrane’ and an ‘oro-pectoral fold’ but he gives no explicit definition. He explains that “the lateral oral fold extends from the rostral cap to the pectoral fin origin”. I understand this to mean the hard, thickened structure (Fig. 1) that extends from the basis of the outer rostral barbel to the origin of the pectoral fin, which may appear as folded (with a groove for part or all its length), not visible in smallest specimens, becoming gradually more distinct with increasing size. I have more difficulties to understand what is the oropectoral membrane, which Roberts described as: “The head may appear either oblong (almost rectangular) or broadly ovate. This depends on whether the oropectoral membrane is folded in or folded out” and “[... the oropectoral fold extends ...] from the corner of the mouth (or rictus of the jaws) to the pectoral fin origin”. The oropectoral membrane is mentioned in none of the species’ descriptions. I do not understand what membrane this could be.</p><p>Freyhof &amp; Serov (2000: 218) also mention the oro-pectoral membrane and refer to the definition of Roberts (1998).</p><p>However, they mention “no skin-fold between oropectoral membrane and ventral surface of head” (p. 221, for S.</p><p>lineolata; p. 225, for S. marmorata; p. 229, for S. pterolineata;</p><p>p. 230, for S. speciosa), and “skin fold between oropectoral membrane and ventral surface of head running from pectoral-fin origin to second rostral barbel” (p. 229, for S.</p><p>diardi; p. 230, for S. elongata; p. 231, for S.</p><p>breviventralis; p. 235, for S. patella). I retain the wording</p><p>‘oro-pectoral fold’ for the hard structure continuing the rostral cap from the base of the posterior rostral barbel to the basis of the anterior pectoral-fin ray. The ‘oropectoral fold’ is also present in S. hypsicrateae and S. Fig. 3. Sewellia pterolineata, CMK 16331, males; mouth, ventral pudens . view. a, 32.8 mm SL; b, 26.7 mm SL. Dotted line shows posterior extent of post-oral pouch. fa, anterior fossa; fp, posterior fossa; Roberts (1998: 273) called the structure made of the posterior mb, mandibular barbel.</p><p>rays of the pelvic fin the ‘pelvic valve’ (Fig. 4). The posterior row of irregular pointed projections (often confused with tubercles). In some species, the extensions appear as a single longitudinal blade (e.g., S. speciosa, S. lineolata), or a blade with several interruptions (e.g., S. pterolineata), or a triangular plate at midlength of ray ( S. patella). These extensions maybe missing (e.g., S. pudens). See Discussion for the details of the different species.</p><p>In all species, pads of unculi are present on the ventral surface of the unbranched pectoral- and pelvic-fin rays, and on the two branches of the about 9 to 12 anterior branched pectoral-fin rays and about 9 to 12 anterior branched pelvic-fin rays. A row of small, blunt tubercles may be present along anterior edge of unculiferous pads of anteriormost rays of both fins. two or three rays of the pelvic fin are adjacent, without or with only narrow membranes between them; they are folded over the preceding rays, between them and the body. These three rays are encased in thick tissue, forming a slender vertical crest along its dorsal margin. The three rays are adnate to the body and partly covered by the pelvic axillary lobe. I have also observed the pelvic valve in Pseudogastromyzon myersi . Beaufortia has fused pelvic fins, but the fins are not fused between the posteriormost ray of each fin. They are fused, but along the penultimate or antepenultimate ray, the rays are turned upward, with several slender branches, and not encased in thick tissues (observed in B. daon, B. kweichowensis, B. leveretti, B. zebroidus; not in B. cyclica).</p><p>Tubercles of a variety of sizes are present on the head, inferior part of the body, and on all fins (except the dorsal fin). Their development seems to be sexually dimorphic. Among the species I examined, large tubercles are present on the cheek, snout and rostral cap in S. elongata, S. pudens, some S. diardi and S. pterolineata (Figs. 7, 10, 11, 12).</p><p>Tubercles and unculi on pectoral and pelvic fins show a variety of development in the different species examined. Small tubercles are usually present on the 3 to 5 anterior pectoral-fin rays. In most species, tubercles are present on some median pectoral-fin rays (usually between rays 15 to 23). In some species, anterior pectoral-fin rays may have a swelling with the posterior side covered with densely set unculi (e.g., S. speciosa, S. lineolata). These rays are arched and rigid, forming a kind of concavity under the anterior part of the fin. In several species, on pelvic-fin rays between about 8 to 15, segments have each a lamellar extension of the bone from the dorsal surface of the ray. These extensions may appear as a crenated ridge (e.g., S. diardi, S. elongata). With increasing size, these extensions may develop as a</p></div>	https://treatment.plazi.org/id/03BD1C70FFA32910FEE6FAB99904C457	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.		Plazi	Kottelat, Maurice	Kottelat, Maurice (2025): Sewellia pudens, a new species of loach from Dakchung Plateau, southern Laos (Teleostei: Gastromyzontidae). Raffles Bulletin of Zoology 73: 304-317, DOI: 10.26107/RBZ-2025-0022
03BD1C70FFA12914FC6CFD199E10CCE6.text	03BD1C70FFA12914FC6CFD199E10CCE6.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Sewellia pudens Kottelat 2025	<div><p>Sewellia pudens, new species</p><p>(Figs. 5–7)</p><p>Holotype. MHNG 2799.022, 49.2 mm SL; Laos: Sekong Prov.: Houay Phouang, in <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=107.27056&amp;materialsCitation.latitude=15.455277" title="Search Plazi for locations around (long 107.27056/lat 15.455277)">Dak Bon</a>, 2 km South of Dakchung; 1187 m asl; 15°27′19″N 107°16′14″E; M. Kottelat et al., 22 May 2011.</p><p>Paratypes. All from Laos: Sekong Province: CMK 22322, 1, 47.4 mm SL; unnamed stream, 1.5 km on road from Dak Ta Oc Noy to <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=107.20305&amp;materialsCitation.latitude=15.360834" title="Search Plazi for locations around (long 107.20305/lat 15.360834)">Dakchung</a> (about 10 km from Dakchung); 1090 m asl; 15°30′43″N 107°19′17″E; 20 May 2011; M. Kottelat et al. — CMK 22381, 9, 32.8–43.8 mm SL; Houay Oy [Xe Nam-Oy on map], large stream, on road from Dakchung to Dak Noi, 5 km from Dakchung, 5 km from Dak Noi; 1164 m asl; 15°31′04″N 107°13′27″E; 21 May 2011; M. Kottelat et al. — CMK 22348, 59, 27.6–43.6 mm SL [+ 8 fixed in ethanol]; CMK 29201, 16, 30.6–46.9 mm SL; ZRC 68312, 10, 30.4–42.8 mm SL; Houay Phouang, in Dak Bon, 2 km South of Dakchung; 1187 m asl; 15°27′19″N 107°16′14″E; 22 May 2011; M. Kottelat et al. — CMK 22379, 2, 30.0– 30.1 mm SL; Houay Champong, in Ban Dak, immediately upstream of confluence with Houay Xe Kaman, 15 km from Dakchung, 4 km after Dak Noi and 4.4 km before Ban Sang Mai; 15°34′24″N 107°13′03″E; 1170 m asl; 22 May 2011; M. Kottelat et al. — CMK 22380, 16, 20.9 –43.0 mm SL; Houay Oy [Xe Nam-Oy on map], 13 km from Dakchung, on road to Ban Tong Siang, 4 km after Ban Tongxiang; 1226 m asl; 15°29′05″N 107°11′07″E; 21 May 2011; M. Kottelat et al. — CMK 29189, 1, 39.9 mm SL; small stream [possibly Nam Voun, near Dak Do on map] about 15 km on road from Dakchung to Sekong; 1130 m asl; 15°21′39″N 107°12′11″E; 23 May 2011; M. Kottelat et al .</p><p>Diagnosis. Sewellia pudens is distinguished from all species of Sewellia by the poorly developed patterning of the body and fins. On the body, black pigments are present in a vague midlateral stripe and 3–8 small saddles on the back, especially on caudal peduncle. Some irregular markings are also present on the body of some specimens, but not forming a clear pattern. The fins of most specimens have no colour marks, except for thin black lining along rays in the dorsal, anal and caudal fins, and, rarely, 1 or 2 faint blotches along lower edge of the caudal fin. The pectoral and pelvic fins have no black patterning. In all the other species of Sewellia,</p><p>the body and paired fins have conspicuous marking (some large specimens may be almost completely dark brown) and the dorsal and caudal fins have several rows of conspicuous black dots. Sewellia pudens is also unique in the genus in having a longitudinal groove on the snout between patches of large tubercles in males. Additional characters useful for its identification, but not unique are: no dorsal extensions or ridges along the dorsal side of the pectoral-fin rays; the pelvic fin not reaching the anal fin; the anal fin not reaching the base of the caudal fin.</p><p>Description. See Figure 5 for general appearance and Table 1 for morphometric data of holotype and 9 paratypes, 38.9–49.2</p><p>mm SL. A moderately elongate Gastromyzontidae with very arched dorsal profile, body depth gradually increasing up to slightly in front of dorsal-fin origin, decreasing under dorsal-fin base. Behind dorsal fin, body depth decreasing regularly until caudal-fin base. Dorsal profile with weakly marked concavity between head and body. Ventral profile straight to slightly concave. Prepelvic part of belly and lower surface of head slightly concave. Head depressed; body very depressed. Interorbital area flat to slightly convex. In lateral view, eye flushed with dorsal profile of head. Snout rounded. Depth of caudal peduncle 1.2–1.5 times in its length, tapering posteriorly, and 1.6–2.0 times in body depth. Largest observed size 49.2 mm SL.</p><p>Dorsal fin with 3 unbranched and 7½ branched rays; distal margin straight to slightly convex; 1st and 2nd branched rays longest. Pectoral fin with 1 unbranched and 23 (1), 24 (2), 25 (7*) or 26 (1) branched rays, rounded, reaching about ⅓ of length of pelvic fin (to axillary pelvic lobe); small tubercles on dorsal side of branched and unbranched rays 1–5; on ventral side, unculiferous pads under 10–12 anterior rays (and their branches), and a row of small, blunt tubercles along anterior edge of unculiferous pads of anterior rays; no axillary pectoral lobe.</p><p>Pelvic fin with 1 unbranched and 18 (8) or 19 (3*) branched rays, rounded, reaching about half of distance to anal-fin origin (slightly beyond anus); no extensions or ridge along dorsal surface of rays (or hidden in thick, opaque tissue); last 3 rays adjacent, folded above preceeding rays to form ‘pelvic valve’; axillary lobe present, free (extremity missing in Fig. 5), extending beyond base of last branched rays; on ventral side, unculiferous pads under 10–11 anterior rays (and their branches), and a row of small unsharp tubercles along anterior edge of unculiferous pads. Anus situated under posterior extremity of pelvic fin, at about half of distance between pelvic-fin base and anal-fin origin.</p><p>Anal fin with 2 unbranched and 4½ branched rays; not reaching caudal fin; distal margin straight; last unbranched ray with a row of tubercles on each side, along whole length. In largest specimens, a row of tubercles on each side of branched rays 1 to 3.</p><p>Caudal fin with 7+8 branched rays; slightly emarginate, tip of lobes rounded, lower lobe longer than upper lobe. Upper 2 and lower 4 principal caudal-fin rays adnate (without membranes) until about one third of their length. Lower principal ray with a row of tubercles on each side; also present along upper principal ray in largest specimens.</p><p>Body entirely covered by scales, except on belly from throat to base of last pelvic-fin rays. Scales embedded in about anterior half of body. All scales with rounded posterior edge. Lateral line complete, extending on caudal-fin base, with 61–69 + 1 pored scales. One tubercle on each scale in lower half of body above anal fin, in some specimens tuberculate scales extending forward until tip of pelvic fin and backwards to caudal-fin base.</p><p>Anterior nare pierced in front side of a flap. Posterior nare adjacent to anterior one, almost entirely covered by flap. Mouth arched, gape about 1.5–2 times wider than long (Fig. 6). Two pairs of rostral barbels and one mandibular barbel at each corner of mouth. Rostral barbels fan-shaped, with 3–6 lobes at tip. Lower lip with low papillae. Oro-pectoral fold present. Mouth structure in smallest available juveniles (about 20 mm SL) as in adult.</p><p>Tubercles: Large males distinguished from females by the presence of conspicuous tubercles on head, body, and fins (based on Roberts, 1998). See above for tubercles on body and fin rays. Conspicuous tubercles on ventral and lateral sides of snout (Fig. 7), missing in median area of dorsal surface of snout. A row of tubercles between snout and nostril. Tubercle patch on side of head divided by a groove extending from below eye, along infraorbital canal of cephalic sensory system, then extending forward halfway between under nostril to tip of snout. Above groove, a patch of large tubercles immediately below eye, smaller tubercles under nostril and around posterior edge of eye. Below groove, patch of large tubercles from snout to below eye. Groove already distinct in specimens about 28 mm SL. A broad patch of tubercles along edge of opercle and between opercle and origin of pectoral fin. On ventral surface, small tubercles near base of 3 anterior rays of pectoral fin, connected with a row of small tubercles along anterior edge of unculiferous pads on rays. Patch of small, low tubercles between side of mouth and origin of pectoral fin may be present. In females, tubercles present but less developed, sometimes minute.</p><p>Colouration. After about 6 weeks in formalin: head and body background colour yellowish brown; ventral surface of head and belly whitish. In most specimens, colour pattern (dark pigments) restricted to an irregular midlateral stripe ending in a vague blotch at caudal-fin base and 3–5 small saddles behind dorsal-fin base, sometimes with 1–2 along base of dorsal fin and 2 in front of fin. In some specimens, some irregular dark brown marks on body. Pelvic and pectoral fins brown, with hyaline margin. Anal fin hyaline. Dorsal fin hyaline, rays light greyish, with spare pigments and thin black outline of rays and segments. Caudal fin hyaline, rays light greyish, with spare pigments and thin black outline of rays and segments; in a few specimens, some black pigments on rays, possibly forming one or two vague blotches near base of 3 lowermost principal rays, but never forming bars or blotches. No apparent sexual dimorphism. Juveniles identical to adults.</p><p>Distribution and habitat. The species has been observed only in tributaries of the Xe Kaman on the Dakchung plateau in Laos (Fig. 8), at altitudes between 1090 and 1226 m asl.</p><p>At the type locality, the Houay Phouang is close to Dakchung village and had a moderate flow of turbid water, with large riffles over sediment covered stones. Few species were present and S. pudens was the most common species, but this may have been a sampling bias because of the turbid water. At the other sites where S. pudens was observed, it was in clear water, flowing over stone or between rocks (Fig. 9). Eight of the other 10 species observed on the plateau were observed ( Devario gibber, Neolissochilus blanci, Onychostoma meridionale, Poropuntius sp., Scaphiodonichthys sp., Annamia normani, Sewellia diardi, Schistura clatrata) (Kottelat, 2017). At four of six localities where it was present, S. pudens was obtained with S. diardi, and at each of these localities S. diardi was most numerous (ratios S. pudens: S. diardi: 9:157, 17:196, 2:5, 1:46). No microhabitat difference between the two species was noted in the field.</p><p>Etymology. The Latin adjective ‘pudens’ means modest, humble, reserved, discreet. It refers to the absence of conspicuous pattern on the body and fins (compared to most other species of the genus) and the absence of ostentatious modification on pectoral- and pelvic-fin rays. Pudens is indeclinable.</p><p>RAFFLES BULLETIN OF ZOOLOGY 2025</p></div>	https://treatment.plazi.org/id/03BD1C70FFA12914FC6CFD199E10CCE6	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.		Plazi	Kottelat, Maurice	Kottelat, Maurice (2025): Sewellia pudens, a new species of loach from Dakchung Plateau, southern Laos (Teleostei: Gastromyzontidae). Raffles Bulletin of Zoology 73: 304-317, DOI: 10.26107/RBZ-2025-0022
