Diagnosis: The greater body depth, 35.1-37.8% of standard length, of Diplotaxodon altus separates it from D. limnothrissa, 22.5-27.8% of standard length, D. argenteus, 27.3-27.6% of standard length, D. macrops, 32.0-34.2% of standard length, D. ecclesi, 31.0% of standard length, and D. longimaxilla, 28.9-32.5% of standard length (Ref. 127500). The presence of 21-26 gill rakers on the outer arch of the ceratobranchial distinguishes it from D. aeneus and D. greenwoodi which both have fewer than 20 gill rakers; the smaller cheek depth, 18.2-20.0% of head length, distinguishes it from D. apogon, 23.2-28.0% of head length (Ref. 127500).

Description: Body laterally compressed and deep; head concave just above large eyes, horizontal eye diameter 30.3-34.0% of head length, vertical eye diameter 29.7-32.0% of head length; lower jaw with slightly convex profile; caudal fin emarginate (Ref. 127500). Small ctenoid scales with 35-37 in lateral series; lower lateral line short and straight; two rows of scales between upper and lower lateral lines at anterior end of lower lateral line; one row of scales between upper and lower lateral lines at posterior end of upper lateral line; one scale row between upper lateral line and posterior insertion of dorsal fin; cheek with 3-4 rows of scales; pored scales posterior to lateral line 0-2 (Ref. 127500). Outer arch of epibranchial with 5-6 gill rakers; outer arch of ceratobranchial with 21-26, with additional axial element (Ref. 127500). Teeth unicuspid, in 2-3 series on upper and lower jaws with inward curve of rows laterally (Ref. 127500).

Colouration: Mature males and females: light copper dorsally to silver toward lateral line; white ventrally; white pelvic fins; caudal fin light grey to clear posteriorly, pectoral fin clear (Ref. 127500).