Hypothesized to be closely related to Poecilia. branneri and P. minima by sharing eight apomorphic conditions: teeth of the external rows of dentary and premaxilla conical; 5-7 teeth on the external rows of dentary and premaxilla; vomer process not longitudinally elongated; tip of gonopodial rays 3 and 4a ankylosed; dorsal fin with 8 rays in males and 7 rays in females; penultimate dorsal-fin ray of male elongated; presence of a black blotch on the posterior portion of the caudal peduncle in both sexes; middle portion of flank with vertical pale gray bars in males. Distinguished from all of its congeners by the presence of a round or slightly vertically elongated post humeral blotch (vs. slightly ventrally dislocated post humeral blotch in P. minima, vertically elongated post humeral blotch in P. parae, P. bifurca and P. picta and post-humeral blotch absent in P. branneri) (Ref. 86528).