Diagnosis: Paretroplus petiti is a deep-bodies Paretroplus and it is distinguished from all congeners, except P. menarambo, by dark brown colouration in combination with the lack of a strong lateral barring pattern (Ref. 78623). It is distinguished from P. menarambo by the absence of a pinstriped pigmentation pattern, which results in the latter species due to conspicuous spotting on scales (Ref. 78623). Further, P. petiti can be distinguished from all congeners by a deep, disk-shaped body and the presence of lateral ridges of scales that are free from the fin membranes over the entire length of the soft dorsal and anal fins (Ref. 78623).