Diagnosis: Haplochromis aureus is a species with an acute snout; acutely pointed oral teeth; very broad interorbital area, interorbital width 56.8-66.6% of head width; very short predorsal distance, predorsal distance 31.7-34.4% of standard length; dominant males light blue with yellow snout, cheeks, and chest (Ref. 128938). Small specimens can be mistaken for Haplochromis pappenheimi or H. pelagicus, but differ from both by a deeper body, body depth 30.7-33.5% of standard length vs. 25.4-31.0%; longer upper jaw, upper jaw length 29.3-35.6% of head length vs. 26.5-29.4%; fewer gill rakers, 12-14 vs. 13-18 (Ref. 128938). It resembles H. mentatus in habitus and overlaps slightly in habitat (H. mentatus mostly restricted to littoral regions), differs by a shorter lower jaw, lower jaw length 41.1-46.4% of head length vs. 43.9-51.0%; more and smaller upper outer teeth, upper outer teeth 48-65 vs. 28-46, and dominant males light blue with yellow cheeks and chest vs. uniformly yellow-green with red flanks (Ref. 128938).

Description: Body oval and shallow; caudal peduncle shallow (Ref. 128938). Head short and narrow with a straight to very weakly convex dorsal outline; snout acute in lateral view with an inclination of 32-37°, and acute in dorsal view; eye average in size; interorbital area very broad; lacrimal deep; cheek shallow; oral jaws average in length, narrow, relatively slim, and with a gentle gape inclination of 26-31°; maxilla extends to vertical through anterior margin of orbit; lips thin (Ref. 128938). Outer oral teeth many, average in size, not embedded in oral mucosa; necks slender, cylindrical, and straight; crowns weakly recurved, acutely pointed, bicuspid with some uni- and tricuspid teeth in small specimens less than 90 mm standard length, unicuspid teeth in large specimens larger than 90 mm standard length; bicuspid teeth acutely pointed and with a protracted major cusp with a very small flange, a small and rounded minor cusp that points straight up, and a narrow cusp gap; dental arcades rounded; outer teeth closely and regularly set with neck-distances of 1/2 neck-width; outer teeth decrease slightly and gradually in size posteriorly; 2-7 posteriormost premaxillary outer teeth small and uni- or tricuspid in small specimens less than 90 mm standard length, unicuspid in large specimens larger than 90 mm standard length; inner teeth small, recurved, uni- or tricuspid, and acutely pointed; tooth bands very slander crescent-shaped with 2-3 rows of inner teeth, narrowing posteriorly until only outer row remains past 3/4 length of tooth band; inner rows closely and regularly set on 1 neck-width from outer row in both jaws, implantation erect; anteriormost teeth in first row slightly larger than remaining (Ref. 128938). Lower pharyngeal bone short, average in width, slim, and shallow over entire length; pharyngeal teeth, very slender, and recurved; major cusps acutely pointed; minor cusp gap straight; minor cusps very small; cusp protuberances very small to absent; teeth in two median longitudinal rows equal in size and form to lateral teeth, about 11-12 in each row; posterior transverse row with 22-25 teeth with a weakly recumbent implantation; major cusp bluntly pointed; minor cusp gap straight to concave; minor cusp very small to absent (Ref. 128938). Chest scales generalised, transition to flank scales gradual; minute scales on proximal half of caudal fin; very rarely 1-3 rows of 3-7 minute scales on proximal parts of dorsal and anal fins; longitudinal line scales 32-34; upper lateral line scales 20-23, lower lateral line scales 8-14; upper transverse line scales 5-6, lower transversal line scales 10-12; caudal peduncle scales 16-19; pelvic-pectoral scales 3-6 (Ref. 128938). Caudal fin truncate; dorsal and anal fins reach to vertical through 1-3 scales anterior to caudal-fin base; pectoral fin reaches to between just anterior to anal opening and first anal fin spine; pelvic fin reaches to anal opening, in dominant males to first anal fin spine; first branched pelvic-fin ray slightly elongated, in dominant males elongated (Ref. 128938). Ceratobranchial gill rakers in outer row of first gill arch closely set, acutely pointed, slender, and simple; posteriormost rakers simple, anvil-shaped, or weakly bifid; epibranchial gill rakers slender and simple (Ref. 128938).

Colouration: Live colouration of dominant males: body light blue; flank mostly with 5-6 vertical stripes; snout, lips, cheek, and chest yellow; belly white; dorsum greenish; nape band faint; lacrimal, vertical preopercular, and supraorbital stripes very faint; eye dark with silver to golden inner ring; pectoral fin hyaline; pelvic fin black; dorsal fin dusky with black lappets and crimson maculations in posterior part; anal fin dusky with crimson distal part and 2-3 large, twice distance between fin rays, orange egg spots with dusky borders; caudal fin dusky with crimson posteroventral part and faint black maculations in dorsal part (Ref. 128938). Live colouration of females and juveniles: dorsal parts of body and head, lacrimal, and lips dark green; ventral parts of body and head white; transition gradual; flank mostly with 5-6 vertical stripes; nape band faint; lacrimal, vertical preopercular, and supraorbital stripes very faint; eye dark with silver to yellow inner ring; pectoral and anal fins hyaline, anal fin with yellow sheen and 1-2 faint spots resembling egg spots; dorsal fin hyaline to dusky, caudal fin dusky with maculation in dorsal part, pelvic fin yellow (Ref. 128938). Preserved colouration: in all specimens, dorsal parts of body and head brown, ventral part of body, operculum, and cheek white; transition rather abrupt at horizontal through lower lateral line; lacrimal, snout and lips dusky; flank often with 5-6 vertical stripes, sometimes with faint mid-lateral and dorsal-lateral bands; lacrimal, supraorbital, and vertical preopercular stripes faint; nostril and interorbital stripes very faint; mental blotch present; pectoral fin hyaline; dorsal fin dusky and with black lappets and black maculations in posterior part; caudal fin dusky; in dominant males branchiostegal membrane black; pelvic fin black; anal fin dusky and with 2-3 large egg spots; in juveniles and females brachiostegal membrane light-coloured; pelvic fin hyaline; anal fin hyaline to faint dusky (Ref. 128938).