Adults measuring >4.33 cm SL differ from all other South Asian Puntius by a combination of the following characters: a black band about as wide as eye across each caudal-fin lobe (faint or absent in adults of the Kallada River population); lower lip continuous, a caudal blotch on 2-5 scales, commencing posterior to anal-fin origin; no distinct markings on body in advance of anal-fin origin. Adult males from the Chalakudy and Kallada River populations with branched dorsal rays prolonged into filament-like extensions. Adults of P. assimilis may be distinguished from P. filamentosus by possessing mouth inferior (vs. subterminal) and maxillary barbels 23.5-33.3% HL (vs. 2.8-8.1%) (Ref. 55036).

Description: Pectoral fin with one simple and 14 branched rays. Lateral line with 19 or 20 scales, 2 pored scales on base of caudal fin (Ref. 55036).