Diagnosis: The presence of bicuspid teeth in the outer rows on both the upper and lower jaws and a moderately sloped vomer block with a swollen rostral tip place this species in Maylandia (Ref. 119465). Male and female M. usisyae are distinguished by an elongate body, body depth 25.9-30.6% of standard length, from all other species in Maylandia, body depth 28.8-40.8% of standard length, except M. tarakiki, body depth 25.8-32.9% of standard length, and M. flavicauda, body depth 23.6-28.5% of standard length (Ref. 119465). It differs from M. tarakiki by a smaller eye, vertical eye diameter 23.1-28.1% of head length vs. 30.2-36.5% in M. tarakiki; and a shorter lower jaw length, lower jaw length 29.9-33.4% of head length vs. 34.8-38.9% on M. tarakiki (Ref. 119465). Based on the colour pattern, male M. usisyae possess a yellow dorsal fin with a black submarginal band, yellow pelvic fins and yellow anal fin with a black leading edge; male M. flavicauda possess black pelvic and anal fins, and a black dorsal fin with yellow/orange spots distally; the ground colouration of male M. flavicauda is blue with 2 light/purple interorbital bars vs. yellow with 2 white/light blue interorbital bars in male M. usisyae; females of M. usisyae cannot reliably be distinguished by colour from those of M. flavicauda; Maylandia flavicauda also possess a deeper preorbital bone, preorbital depth 18.0-26.9% of head length, and a longer snout, snout length 34.3-47.3% of head length, which are 17.6-21.2% and 32.0-37.6% in M. usisyae respectively (Ref. 119465).

Description: Elongate species, body depth 25.9-30.6% of standard length, with greatest body depth at base of seventh or eight dorsal-fin spine (Ref. 119465). Dorsal body profile with gradual curve to caudal peduncle with highest point at seventh or eight dorsal-fin spine, greater body depth in males than in females; ventral body profile between pelvic and anal fins flat with upward curve to caudal fin; dorsal head profile straight to slightly concave between snout tip and interorbital area, making 40-50° angle with body axis, greater angle in males than females, then round to dorsal-fin origin (Ref. 119465). Snout short with isognathic jaws; teeth on lower jaw in 3-4 rows; upper jaw in 3-4 rows; outer rows bicuspid; inner rows tricuspid (Ref. 119465). First 3-4 dorsal-spines gradually longer posteriorly with first spine less than half length of fourth spine; last dorsal-fin spine slightly longer than fourth spine; soft dorsal fin with subacuminate tip, third or fourth ray longest, to about base of caudal fin in both males and females; pectoral fin rounded, paddle-shaped; first ray of pelvic fin longer than other rays; anal fin with 3 spines progressively longer posteriorly; third or fourth ray longest, length beyond base of caudal fin in males and to base of caudal fin in females; caudal fin subtruncate to emarginate (Ref. 119465). Lateral scales large, ctenoid; small cycloid scales on breast and belly; cheek with 5 rows of small scales; dorsal fin and anal fin with narrow proximal band of tiny scales; tiny scales from base to 50% length of caudal fin (Ref. 119465).

Colouration: Males in territorial colour with brown/yellow ground colouration and faint light brown bars; head brown with 2 light blue/white interorbital bars and purple highlights; throat light blue; dorsal fin black/yellow proximally, black distally with light blue lappets; anal fin dark blue with 5-6 yellow ocelli and black/blue margin; pectoral-fin rays brown with clear membranes (Ref. 119465). Females with brown ground colouration and 2-3 faint dark brown bars with purple/blue highlights on edge of scales; belly and breast beige/brown; head dark brown; black/gray opercular spot; interorbital bars purple/brown; dorsal fin yellow/light brown proximally and black distally; pectoral fin and pelvic fin brown/purple; caudal fin light brown with dark brown ventral and dorsal margins (Ref. 119465).