The lower portion of the dorsal caudal-fin lobe with conspicuous ocellated caudal-fin blotch which is an autapomorphy which separates the new species from all congeners, and in fact from all remaining Characidae. The other members of Hemigrammus differ by having black pigmentation on the caudal fin either confined to the caudal-fin base (e.g., species belonging to the Hemigrammus ocellifer and Hemigrammus tridens groups, sensu), or as a discrete terminal bar (Hemigrammus marginatus), or finally as symmetrically-arranged black spots on the dorsal and ventral caudal-fin lobes (Hemigrammus bleheri and Hemigrammus rhodostomus) (Ref. 78749).

Description: D ii,9; A iv or v, 19, 20, or 22; P i10, 11, or 12; V i7. Longitudinal series scales, including perforated scales 30, 31, 32, 33 (Ref. 78749).