Sisor chennuah Ng and Lahkar, 2003

Ng, H. H., 2003, A revision of the south Asian sisorid catfish genus Sisor (Teleostei: Siluriformes), Journal of Natural History 37 (23), pp. 2871-2883 : 2876-2877

Sisor chennuah Ng and Lahkar n. sp.

(figures 2a, 4a, 5) Sisor rhabdophorus (non Hamilton, 1822): Motwani et al., 1962: 21; Qureshi, 1965: 35,

figure 90 (in part?); Ataur Rahman, 1989: 207, figure 123; Mamnur Rashid et al., 1997:

137; Jayaram, 1999: 301 (in part).

Material examined

H  . NRM 40420, 98.1 mm SL; India: Assam State, Brahmaputra River drainage, Dibrugarh, from aquarium trade; F. Fang and A. Roos, 19 January 1998 .

P    . NRM 45253, 86.9 mm SL; data as for holotype .

Diagnosis

Sisor chennuah can be distinguished from S. rabdophorus and S. rheophilus in having a deeper body (body depth at anus 5.6–5.8% SL vs 4.2–5.4). It further differs from S. rheophilus in having a wider head (15.7–15.9% SL vs 14.5–14.8), shorter snout (54.0–55.9% HL vs 56.2–60.3), smaller eye (9.9–11.4% HL vs 13.2–16.3), fewer serrations on posterior edge of pectoral spine (10 vs 17–22) and wider nuchal plate (width 1.1–1.2 times length vs width equal to length; figure 2a), and from S. torosus in having a more slender body (body depth at anus 5.6–5.8% SL vs 6.0–7.8).

Description

General appearance as for genus. In % SL: body depth at anus 5.6–5.8, predorsal length 32.2–34.4, preanal length 62.2–68.1, prepelvic length 32.0–35.3, prepectoral length 15.8–17.9, length of dorsal-fin base 12.2–15.3, length of dorsal spine 7.9–9.5, length of anal-fin base 6.5–6.9, length of pelvic fin 13.5–14.4, length of pectoral fin 20.0–21.2, length of pectoral spine 16.9–18.2, depth of caudal peduncle 1.4–1.6, length of caudal peduncle 22.6–25.1, length of caudal fin 12.5–12.7, head length 20.3–22.6, head width 15.7–15.9, head depth 8.0–8.1; in % HL: snout length 54.0–55.9, interorbital distance 22.1–22.7, eye diameter 9.9–11.4, length of maxillary barbel 54.5–71.0, length of inner mandibular barbel 36.5–51.7, length of outer mandibular barbel 52.3–66.5. Branchiostegal rays five (2). Vertebrae 19 + 13 = 32 (1) or 20 + 14 = 34 (1). Lateral line ossicles 78–79. Nuchal plate with a short, broad central process, width 1.1–1.2 times length (figure 2a).

Fin-ray counts: dorsal I, 6 (2); pectoral I, 10, i (1) or I, 11 (1); pelvic i, 5 (2); anal ii, 4 (2); caudal 5/6 (1) or 5/7 (1). Anterior edge of pectoral spine with 30–31 long and narrow serrations on anterior edge, and 10 smaller, more recurved serrations on posterior edge (figure 4a).

Etymology From the local name of the fish (Chennuah). Used as a noun in apposition.

Distribution Known from the Brahmaputra River drainage.