This species is distinguished from its congeners (except P. xanthurus) by having the following characters: precaudal vertebrae 11?12 (vs. 13 or more, rarely 12); total vertebrae 28?29 (vs. 30 or more in P. medius, P. ovatus, P. simillimus and P. snyderi); body height 58.5?79.0% SL (vs. 33.0?52.% SL in P. burti, P. simillimus, P. snyderi, P. ovatus and P. triacanthus); without series of pores along the front half of body under the dorsal fin (vs. 17?25 in P. triacanthus); a moderately falcate dorsal fin (vs. not falcate in P. triacanthus, or conspicuously falcate in P. paru); specimens larger than 9.0 cm SL, has an extremely falcate anal fin (vs. not falcate or moderately falcate in P. burti, P. simillimus, P. snyderi, P. ovatus and P. triacanthus); further distinguished from sympatric P. xanthurus by the lack of a conspicuous dark spot over the eyes, from snout to nape (vs. a conspicuous dark spot over the eyes, especially distinct in fresh specimens); in specimens smaller than 11.0 cm SL, orbital diameter is 1.6?5.0 in anal-fin height (vs. 5.1?8.0); in specimens larger than 10.9 cm SL, orbital diameter is 3.2?5.2 in anal-fin height (vs. 5.5?9.2), 2.9?3.8 in pectoral-fin height (vs. 3.9?5.9), and 0.8?1.4 in post-orbital length (vs. 1.5?2.3); further distinguished from P. paru by having a moderately long to short dorsal fin and relatively long caudal fin lobe, with length of lower lobe more than 1.2 times the length of the dorsal fin (vs. 1.2 times the length or less) (Ref. 116249).