Hassar gabiru is distinguished from H. orestis and H. wilderi by having two weakly-branched diverticula restricted to each side of anterior chamber of gas bladder (rarely one extra pair on posterior chambers) (vs. gas bladder with many well-branched diverticula along margins of entire bladder); and gas bladder rounded posteriorly (vs. gas bladder triangular posteriorly, each posterior chamber extended posteriorly into a short terminal diverticulum sharing medial septum with its pair). Hassar gabiru is further distinguished from H. orestis by having 11th through 15th, modally 13th, midlateral scute as the anteriormost with median thorn (vs. 1st through 8th, modally 3rd), tip of upper caudal-fin lobe not darkened (vs. usually darkened), body depth at dorsal-fin origin 24.3-33.1%, mean 25.8% SL (vs. 16.8-22.2%, mean 21.1% L), body depth at anal-fin origin 15.9-20.7%, mean 17.3% SL (vs. 10.0-14.7%, mean 13.1% SL), and caudal peduncle depth 6.6-8.6%, mean 7.1% SL (vs. 4.3-6.4%, mean 5.5% SL). Hassar gabiru is distinguished from H. affinis by having the distal tip of the first branched dorsal-fin rays and membranes pale (vs. first branched dorsal-fin rays and membranes distally darkened); and lateral diverticula on the gas bladder fingerlike, weakly-branched in large specimens (vs. rounded, rarely branched in large specimens) (Ref. 87857).