Phallobrycon and Bryconadenos are the only members of the Clade A characids that possess a combination of intumescent glandular tissue present on the anterior part of the anal fin and pelvic-fin hooks absent in sexually mature males. This species can be diagnosed by the following characters: the glandular tissue is associated with specially developed spines on some anal-fin rays. Two developed spines are present on median unbranched portions of fifth, sixth and seventh anal-fin rays which are larger and separated from the close-set smaller hooks that appear on distal portions of the anterior anal-fin rays of Phallobrycon, and different from those found on distal portions of several anal-fin rays of many characids. Large spines and small hooks are never found together on any anal-fin ray in Phallobrycon; presence of a simple concentration of glandular tissue on the anterior part of the anal fin; and presence of a developed urogenital papilla in male specimens (Ref. 81937).

Description: Dorsal fin ii, 8; anal fin iv, 18-23; pectoral fin i, 11-13; pelvic fin i, 7 (Ref. 81937).