Sisor Hamilton 1822

Sisor Hamilton, 1822

Fig. 13

Sisor Hamilton, 1822: 208, 379. (Type species Sisor rabdophorus Hamilton, 1822, by monotypy). Gender masculine.

Diagnosis: Series of bony plates extending from dorsal fin to base of caudal fin; spine in adipose fin; uppermost caudal-fin ray long, more than half length of body; branchiostegal membranes broadly fused to isthmus; outer and inner mental barbels widely separated, with origin of outer barbels anterior to origin of inner barbels; minute teeth in lower jaw, dentition essentially consisting of roughened plate; large serrations on anterior margin of pectoral spine; well-developed maxillary barbel membrane; palatal teeth absent.

Sisor is distinguished from erethistids and all other sisorids by having a series of bony plates extending from the dorsal fin to the base of the caudal fin, and an adipose fin with a spine. It is distinguished from all other Sisorinae by having the uppermost caudal-fin ray long (vs. short), more than half the length of the body; outer and inner mental barbels widely separated, with the origin of the outer barbels anterior to the origin of the inner barbels (vs. nearly in a straight line in Gagata, origin of inner mental barbels anterior to origin of outer mental barbels in Bagarius and Gogangra, and either nearly in a straight line or origin of inner mental barbels anterior to origin of outer mental barbels in Nangra), by having minute teeth in the lower jaw (dentition essentially consisting of a roughened plate vs. teeth of the lower jaw markedly heterodont in Bagarius, and small and conical in Gagata, Gogangra, and Nangra), and by having large serrations on the anterior margin of the pectoral spine (vs. no serrations in Bagarius, Gagata, and Nangra, and small serrations in Gogangra).

Sisor is further distinguished from Bagarius, Gogangra and Nangra by having the branchiostegal membranes broadly fused to the isthmus (vs. free from the isthmus). Sisor is further distinguished from Gagata and Gogangra by having a well-developed maxillary barbel membrane, and from Nangra by its lack of palatal teeth and short maxillary barbel not reaching the pectoral-fin base (vs. barbel reaching to at least the pelvic-fin base).

Description: Dorsal fin with 1 spine, 5-6 dorsal rays; pectoral fin with 1 spine, 9-11 rays; 6-8 pelvic-fin rays; 4-6 anal-fin rays. Head moderately narrow, strongly depressed. Body extremely narrow, strongly depressed. Eyes small, dorsolateral, subcutaneous. Maxillary barbel not extending posteriorly beyond head; barbel with well-developed membrane, stiff base. Coracoid process present but short. Pectoral-fin spine strongly serrate anteriorly and posteriorly. Dorsal-fin spine finely serrate anteriorly, smooth posteriorly. No thoracic adhesive apparatus. Paired fins non-plaited.

Distribution: Indus drainage, Pakistan, east to the Ganges and Brahmaputra drainages, India (Ng, 2003; Vishwanath & Darshan, 2005).