Sisor Hamilton, 1822

Alfred W. Thomson & Lawrence M. Page, 2006, Genera of the Asian Catfish Families Sisoridae and Erethistidae (Teleostei: Siluriformes)., Zootaxa 1345, pp. 1-96 : 37-38

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).