Paracanthocobitis triangula, Page, 2017

Page, Lawrence M., 2017, A revision of the Paracanthocobitis zonalternans (Cypriniformes: Nemacheilidae) species complex with descriptions of three new species, Zootaxa 4324 (1), pp. 85-107 : 101-103

Paracanthocobitis triangula , new species

Wedged Zipper Loach

Fig. 10

Holotype. UMMZ 250272 , 28.6 mm SL, female, Bangladesh, Meghna drainage, 25.183N, 89.983E, 21 February 1978 .

Paratypes. Bangladesh: Meghna drainage: CAS 235899 , 1 , 23.4 mm SL, Sylhet, Nur Nody Stream, upstream from Lubha River at Nihalpur Village , 25.036N, 92.306E, 24 January 1998 ; UMMZ 208784 , 13 (10 ex.), 25.8– 29.2 mm SL, same locality and date as holotype ; UMMZ 208629 , 1 , 24.6 mm SL, Sylhet, Dauki / Piyain Gang River , 25.101N, 91.753E, 19 February 1978; UF 188249, 3, 26.1–28.4 mm SL, same locality and date as holotype .

Diagnosis. Paracanthocobitis triangula is distinguished from all other species of Paracanthocobitis by combination of incomplete lateral line ending near dorsal-fin insertion; 9½–10½ branched dorsal-fin rays; axillary pelvic lobe present; series of black blotches, sometimes overlain with faint dusky stripe along side of body not obscuring lateral blotches, ending just beyond dorsal-fin insertion; small black triangular blotch in ocellus on upper margin of caudal-fin base; black pigment of the midlateral stripe not extending onto pectoral-fin base; no marmorated pattern between dorsal saddles and lateral blotches; dorsal saddles usually extending ventrally just past faint lateral stripe, usually connecting to lateral blotches; 8 branched upper caudal-fin rays.

Description. Meristic and morphometric data are in Tables 4 and 5. Body deepest just anterior to dorsal-fin origin; slightly compressed before dorsal fin, strongly compressed postdorsally. Head depressed, snout gently rounded to slightly pointed when viewed dorsally or laterally. Dorsal-fin origin far in front of pelvic-fin origin; distal margin convex. Pectoral fin not reaching pelvic fin; pelvic fin not reaching anal fin; caudal fin emarginate. Lateral line incomplete, reaching at most to just past dorsal-fin insertion with 20–37 pores. Axillary pelvic lobe present. Mouth arched with heavily papillated lips; upper lip with 3–5 rows of papillae, continuous with large pads on lower lip. Three pairs of barbels; inner rostral barbel extends to or slightly past base of maxillary barbel, maxillary barbel and outer rostral barbel extend to or slightly past eye. Body covered with scales; 9½ (1 specimens)–10½ (10 specimens) branched dorsal-fin rays; 9–10, usually 9, pectoral-fin rays; 6 pelvic-fin rays; 5½ branched anal-fin rays; 8 branched upper caudal-fin rays; 8 branched lower caudal-fin rays. Suborbital flap in male. Maximum SL 29.2 mm female.

Body yellow-brown with 10–12 dark brown to black blotches along lateral line sometimes overlain with faint dusky stripe not obscuring lateral blotches, ending just beyond dorsal-fin insertion; 12–14 small dark brown dorsal saddles uniform, equal to or wider than interspaces, usually extending ventrally just past lateral stripe and connecting to lateral blotches. Dark spots and blotches on head; uninterrupted black bar from eye to tip of snout.

Ocellus with small black triangular blotch in center, near upper margin of caudal peduncle; 3–6 concentric rows of dark spots in dorsal fin, 2–3 rows of dark spots in anal fin, 4–6 dark bands on caudal fin. Black lateral stripe not extending onto pectoral-fin base.

Comparisons. Paracanthocobitis triangula differs from all other species of Paracanthocobitis except P. zonalternans , P. phuketensis , P. nigrolineata , and P. marmorata in having an incomplete lateral line ending near the dorsal-fin insertion (vs. lateral line to the end of the caudal peduncle) and 9½–10½ (vs.>10½) branched dorsal-fin rays. Paracanthocobitis triangula differs from P. zonalternans , P. phuketensis , P. nigrolineata , and P. marmorata in having a small black triangular (vs. circular or teardrop-shaped) blotch on the upper margin of the caudal-fin base. Paracanthocobitis triangula further differs from P. zonalternans in lacking black pigment extending from the lateral stripe onto the pectoral-fin base, from P. phuketensis in having an axillary pelvic lobe (vs. usually absent, occasionally rudimentary), and from P. nigrolineata in not having a black stripe along the side of the body with black pigment from the stripe extending onto the pectoral-fin base. Paracanthocobitis triangula further differs from P. marmorata in having an axillary pelvic lobe and in not having a marmorated pattern between the dorsal saddles and lateral blotches.

Distribution. Paracanthocobitis triangula is known from the Brahmaputra (Jamuna) and Meghna drainages of Bangladesh ( Fig. 5 ).

Etymology. The epithet triangula refers to the usual presence of a small black triangular blotch in the ocellus on the upper margin of the caudal peduncle.

Figures

FIGURE 5. Localities of examined specimens of Paracanthocobitis.

FIGURE 10. Type specimens of Paracanthocobitis triangula. (A) Dorsal and lateral views of holotype, UMMZ 250272, Meghna drainage, Bangladesh, 28.6 mm SL; (B) Dorsal and lateral views of paratype, CAS 235899, Meghna drainage, Bangladesh, 23.4 mm SL.