The only member of the subfamily Anostominae with a single longitudinal stripe. It also lacks transverse bars across the dorsum. Resembles P. gracilis but is distinguished by the following characters: a dark horizontal stripe along the lower half of the lateral-line scale row and the upper half of the row adjoining; four branchiostegal rays; two pores on the sensory canal of the nasal bone between its anterior and posterior openings; four pores associated with the sensory canal of infraorbital one and arranged in an approximate square; nearly complete closure of the metapterygoid/quadrate fenestra; absence of a posterior process of the ectopterygoid running ventral to the palatine in lateral view; presence of a dorsal process of the mesopterygoid that wraps around the posterior of the palatine; and a palatine with a high arch and thick, blocklike morphology (Ref. 55429).

Description: Dorsal fin typically with three unbranched rays and 10 branched and segmented rays; anal fin typically with three unbranched rays and eight branched and segmented rays; pectoral fin with 13-17 rays; pelvic fin typically with 9 rays, three specimens with 8 rays (Ref. 55429)..