This species is distinguished from its congeners except H. sternoptychum, by the pattern of abdominal plates, consisting of a pair of slender plates posterior to the coracoids followed by a series of 1-3 unpaired medial abdominal plates (vs. 2-3 series of abdominal plates), by having the posterior process of the coracoids strongly curved, the distal tip pointing dorsally (vs. posterior process smoothly curved, with distal tip pointing posterodorsally), and by the absence of basipterygium fenestrae (vs. with basipterygium fenestrae). It is distinguished from H. sternoptychum by the absence of thoracic plates and fewer total lateral plates 20-22 (20) (vs. 21-22 (21)), fewer dentary teeth 20-31 (24) (vs. 21-37 (30)), narrow dorsal interorbital distance with mean dorsal interorbital distance of 58.5 (vs. 63.5), pelvic fin placed more anteriorly and mean abdominal length 12.7 (vs. 15.5), shorter pectoral fin; length not reaching anal-fin origin with mean pectoral-fin spine length 29.8 (vs. 39.3), and by the absence of marginal odontodes (vs. marginal odontodes present in adults longer of 35 mm SL) (Ref. 84367).