Diagnosis: Nothobranchius occultus can be distinguished from all other species of the genus Nothobranchius by the following unique combination of characters: 15-18 dorsal fin rays; 15-18 anal fin rays; 26-29 scales in longitudinal series; relatively long pelvic fin, tip reaching anal fin; terminal portion of snout on ventral profile wide and rounded; body, paired and unpaired fins of male completely dark red brown in preserved specimens (Ref. 97568).

Description: Dorsal profile convex from snout to posterior extremity of dorsal fin base; ventral profile convex, slightly concave on caudal peduncle posterior to dorsal and anal fins (Ref. 97568). Maximum body depth measured at base of pelvic fin (Ref. 97568). Snout slightly pointed, mouth directed upwards, lower jaw longer than upper, posterior end of rictus at the same level or slightly below centre of eye (Ref. 97568). Branchiostegal membrane projecting from opercle, distal edge slightly wrinkled (Ref. 97568). Tip of dorsal and anal fins rounded, tips with rudimentary filamentous rays; dorsal fin with sporadic papillate contact organs, anal fin with many papillate contact organs distributed over fin rays; origin of dorsal and anal fins posterior to mid-body; dorsal fin rays 15-18; anal fin rays 15-18; pelvic fins long, tips reaching anal fin base; caudal fin subtruncate (Ref. 97568). Longitudinal series of scales 26-29 + 2-3 on caudal fin base; cephalic squamation pattern variable (Ref. 97568). Anterior neuromast series of the 'open' type; central series in shallow groove with low lobes; posterior cephalic neuromast series reduced; preopercular neuromast system in open groove, distal ridge slightly overlaps opercle; one neuromast on each scale of median longitudinal series (Ref. 97568).

Colouration: Colouration in life of males and females unconfirmed; a generalized bright red colouration reported for males, a generalized pink colouration reported for females (Ref. 97568). In preservative, males with body scales dark red brown; dorsal fin dark red brown; anal fin dark red brown; caudal fin dark red brown; pelvic fins dark red brown; pectoral fins dark red brown; iris black (Ref. 97568). In preservative, females with body light brown; unpaired and paired fins whitish/yellowish; iris black (Ref. 97568).