Glyptothorax prionotos, Ng & Kottelat, 2023

Ng, Heok Hee & Kottelat, Maurice, 2023, Glyptothorax prionotos, a new sisorid catfish from Myanmar and Thailand (Teleostei: Siluriformes: Sisoridae), Journal of Natural History (J. Nat. Hist.) 57 (25 - 28), pp. 1331-1345 : 1331-1345

Glyptothorax prionotos sp. n.

urn:lsid:zoobank.org:act:F7AA921F-7E03-4C4B-9638-63260AA8C66A ( Figure 1 )

Glyptothorax aff. trilineatus – Ng 2015: 152; Boyd et al. 2023: 326.

Type material

Holotype. ZRC 62915 , 65.6 mm SL; Thailand: Tak Province, Mae Nam Moei in vicinity of Ban Wa Le , 16.290°N, 98.706°E; S.H. Tan and N. Sivasothi, 19 March 1996.

Paratypes. CMK 14785 (1), 43.3 mm SL; Thailand: Mae Hong Son Province, Nam Mae Pai drainage, Nam Lang in Ban Mae Lang, about 5 km west of Ban Soppong , small endorheic basin, 19.539°N, 98.218°E; M. Kottelat and K. Kubota, 11 April 1998. CMK 14791 (1), 51.1 mm SL; Thailand: Mae Hong Son Province, Nam Mae Pai drainage, Nam Lang , about 2 km SE of Ban Soppong, 19.504°N, 98.277°E; M. Kottelat and K. Kubota, 11 April 1998. CMK 14758 (1), 81.9 mm SL; Thailand: Mae Hong Son Province, Nam Mae Pai drainage, Huai San, about 1 km on turnoff N to Ban Ma Sang at Km 21 on road from Mae Hong Son to Pai , 19.441°N, 97.997°E; M. Kottelat and K. Kubota, 10 April 1998. CMK 14726 (1), 70.0 mm SL; Thailand: Mae Hong Son Province, Mae Nam Yuam drainage, Nam Mae La Ka, downstream of Ban Nong Hang, 18.648°N, 97.938°E; M. Kottelat and K. Kubota, 9 April 1998. CMK 14721 (2), 53.2–60.3 mm SL; Thailand: Mae Hong Son Province, Mae Nam Yuam drainage, Nam Mae La Noi at Ban Yang Huai Malefai , 18.381°N, 97.964°E; M. Kottelat and K. Kubota, 9 April 1998. CMK 16246 (2), 57.0– 60.2 mm SL; Thailand: Mae Hong Son Province, Nam Mae Sariang at Ta Nam Ung Mae Sariang , 18.205°N, 98.000°E; M. Kottelat et al., 9 April 2000. ZRC 41283 (1), 51.5 mm SL; Thailand: Tak Province, Huai Mae Cha Wang through Highway 105, 17.573°N, 97.953°E; S.H. Tan and N. Sivasothi, 20 March 1996. ZRC 41282 (2), 59.2–65.1 mm SL; Thailand: Tak Province, Mae La S of Ban Tha Song Yang, closer to confluence with Huai Nok Kok, which drains into the Mae Nam Moei , 17.166°N, 98.344°E; S.H. Tan and N. Sivasothi, 20 March 1996. CMK 14668 (1), 47.7 mm SL; Thailand: Tak Province, Mae Nam Moei drainage, Mae Nam Charao at and upstream of Ban Thung Makham Pom , 16.976°N, 98.651°E; M. Kottelat and K. Kubota, 7 April 1998. ZRC 41265 (8), 40.2–58.9 mm SL; data as for holotype. ZRC 41288 (5), 42.1– 59.7 mm SL; locality as for holotype; S.H. Tan and N. Sivasothi, 20 March 1996. CMK 14688 (2), 51.6–70.0 mm SL; Thailand: Tak Province, Mae Nam Moei at Ban Wa Le , 16.290°N, 98.706°E; M. Kottelat and K. Kubota, 7 April 1998.

Diagnosis

Glyptothorax prionotos differs from Indochinese congeners except for G. coracinus , G. deqinensis , G. forabilis , G. granosus , G. granulus , G. interspinalum , G. irroratus , G. lanceatus , G. lairamkhullensis , G. laosensis , G. longicauda , G. longinema , G. porrectus , G. schmidti , G. trilineatus , G. ventrolineatus , G. viridis , G. yuensis and G. zanaensis in having a uniformly dark-coloured body with pale mid-dorsal stripe (vs unevenly coloured, or mottled, body with pale or dark bands and patches or spots in all other congeners). It is distinguished from G. coracinus , G. deqinensis , G. forabilis , G. interspinalum , G. irroratus , G. laosensis , G. porrectus , G. schmidti and G. trilineatus in having a serrated (vs smooth) posterior margin of the dorsal spine ( Figure 2 ), from G. lairamkhullensis and G. viridis in lacking (vs having) plicae on the ventral surfaces of the first pelvic-fin ray and the skin covering the pectoral spine, and from the remaining congeners ( G. granosus , G. granulus , G. lanceatus , G. longicauda , G. longinema , G. ventrolineatus , G. yuensis and G. zanaensis ) in having a unique combination of the following characters: head length 23.6–27.0% SL, head width 19.2–21.4% SL, TAA without anteromedial striae or ridges extending to gular region and with caudally open triangular medial pit extending one-third to half TAA length, 7–10 serrations on posterior edge of pectoral spine, dorsal-fin spine length 12.2– 15.6% SL, triangular anterior nuchal plate element without saddle-shaped lateral expansions of pterygiophores, pale spots only at lateral tips of nuchal plate elements, body depth at anus 14.0–17.4% SL, dorsal to adipose distance 23.6–28.1% SL, distally expanded neural spines of vertebrae between dorsal and adipose fins, length of adipose-fin base 14.1–17.7% SL, post-adipose distance 13.1–17.0% SL, caudal peduncle length 16.6–19.4% SL, caudal peduncle depth 8.0–9.8% SL, caudal-fin length 23.6–28.1% SL, and 35–37 vertebrae.

Description

Morphometric data in Table 1 . Head depressed; body subcylindrical. Dorsal profile rising evenly from tip of snout to origin of dorsal fin, then sloping gently ventrally from origin of dorsal fin to end of caudal peduncle. Ventral profile straight to anal-fin base, then sloping gently dorsally from anal-fin base to end of caudal peduncle. Anus located at vertical through posterior third of adpressed pelvic fin; urogenital openings located at vertical through posterior edge of adpressed pelvic fin. Skin tuberculate, with tubercles of uneven sizes on sides of body and caudal peduncle. Lateral line complete and midlateral. Vertebrae 18 + 17 = 35 (1), 18 + 18 = 36 (1), 19 + 17 = 36* (4), 19 + 18 = 37 (1) or 20 + 17 = 37 (1).

Head depressed and broad, triangular when viewed laterally. Snout prominent. Anterior and posterior nares large and separated only by base of nasal barbel. Gill opening broad, extending from ventral margin of post-temporal to isthmus. Bony elements of dorsal surface of head covered with thick, tuberculate skin. Eye ovoid, horizontal axis longest; located entirely in dorsal half of head.

Barbels in four pairs. Maxillary barbel long and slender, extending to base of second pectoral-fin ray. Nasal barbel slender, extending to anterior orbital margin. Inner mandibular barbel extending to midway between its base and that of pectoral spine. Outer mandibular barbel extending nearly to base of pectoral spine.

Mouth inferior, premaxillary tooth band partially (approximately half) exposed when mouth is closed. Oral teeth small and villiform, in irregular rows on all tooth-bearing surfaces. Premaxillary teeth appearing in single broad semilunate band. Dentary teeth in a single crescentic band, consisting of two separate halves tightly bound at midline.

TAA consisting of striae in an ovate field ( Figure 3 ) extending from isthmus to posterior limit of pectoral-fin base; anterolateral edges of adhesive apparatus gently convex. Triangular medial pit posteromedial, extending forward for one-third to half length of TAA.

Dorsal fin located above anterior third of body, with I,6 (9) rays; fin margin concave; spine short and straight, posterior margin with 3–5 small serrations. Adipose fin with anterior and posterior margins nearly straight. Caudal fin strongly forked, with lobes of nearly equal length and i,7,8,i (9) principal rays. Procurrent rays symmetrical and extending only slightly anterior to fin base. Anal-fin base vertically opposite adipose-fin base. Anal fin with straight anterior and slightly concave posterior margins; with iii,9,i (2), iv,8,i (1), iv,9* (4), iv,9,i (1), or iv,10 (1) rays. Pelvic-fin origin posterior to vertical through posterior extremity of dorsal-fin base. Pelvic fin with slightly convex margin and i,5 (9) rays; tip of adpressed fin not reaching anal-fin origin. Pectoral fin with I,8,i (1), I,9 (4), I,9,i (3) or I,10* (1) rays; posterior fin margin slightly concave; anterior spine margin smooth, posterior margin with 7–10 serrations.

Coloration

In 70% ethanol: dorsal and lateral surfaces of head and body brown, fading to beige on ventral surfaces. Nuchal plate paler, with small ovoid cream spot at lateral tip. Thin, cream mid-dorsal stripe present, extending from base of last dorsal-fin ray to origin of adipose fin. Thin, cream midlateral stripe present in some individuals, extending from just behind opercle to base of caudal fin ( Figure 4 ). Pectoral and pelvic fins with brown on base of fin rays and hyaline posterior margin. Anal fin with brown base and large subdistal brown patch on anterior half of fin. Adipose fin brown, with anterior quarter pale, and hyaline distal margin. Caudal fin with brown fin rays and darker brown band at its base, hyaline distally and tip of lobes cream. Maxillary and nasal barbels brown dorsally, beige ventrally. Mandibular barbels beige.

In life: body blackish brown.

Habitat

Streams with fast current over stones, clear water.

Distribution

Glyptothorax prionotos is known from the Nam Mae Pai, Nam Mae Yuam and Mae Nam Moei drainages, all of which are left-bank tributaries of the Salween River in western Thailand and southern Myanmar ( Figure 5 ). It is very likely to be found in other left- and right-bank tributaries of the Salween in the same general area.

Etymology

The Greek adjective πρΙΟΝωτός means ̍made like a saw̾ or ̍serrated̾. This is used in reference to the serrated dorsal spine, which is a major diagnostic character of this species. The specific epithet is indeclinable.

Figures

Figure 1. Glyptothorax prionotos, holotype, ZRC 62915, 65.6 mm SL; Thailand: Mae Nam Moei. Dorsal, lateral and ventral views.

Figure 2. Schematic illustration of dorsal-spine morphology in: (a) Glyptothorax prionotos, CMK 16246, paratype, 60.2 mm SL; (b) most Indochinese congeners (G. porrectus, CMK 25460, paratype, 70.9 mm SL illustrated). Images not to scale.

Figure 3. Thoracic adhesive apparatus of Glyptothorax prionotos, holotype, ZRC 62915, 65.6 mm SL.

Figure 4. Lateral view of Glyptothorax prionotos, paratype, ZRC 41288, 52.4 mm SL, showing faint midlateral stripe on body.

Figure 5. Map showing collection localities of Glyptothorax prionotos. Each circle may represent more than one locality. The open circle represents the type locality.