Pethia rutila can be distinguished from all species of Pethia occurring in the Ganges-Brahmaputra drainage, Kaladan drainage and the Chindwin-Irrawaddy drainage, except P. expletiforis, P. macrogramma, P. stoliczkana and P. tiantian, in having a complete lateral line. It differs from all its congeners by the combination of the following characters: a black caudal-peduncle blotch extending over scales 16-18 or 17-19 of the lateral line centered above the insertion of the last anal-fin ray; an inconspicuous black humeral spot on the scale row below the 3rd and 4th lateral-line scales; 8 or 9 predorsal scales; 4½ scales between dorsal-fin origin and lateral line, and 3½ scales between lateral line and pelvic-fin origin (Ref. 96523).

Description: Dorsal-fin rays ii-iii,8; anal-fin rays ii-iii,5; pectoral-fin rays i,12-13; pelvic-fin rays i,8; ½4/1/3½ scales in transverse line from dorsal-fin origin to pelvic-fin origin; gill rakers on the first gill arch 1 or 2 on epibranchial, 1 at angle and 8 or 9 on ceratobranchial (Ref. 96523).