Diagnosis: Nothobranchius elucens is distinguished from all other members of the genus by the following characters in males: body colouration golden-grey with brown scale margins creating irregular vertical stripes on trunk, anal fin yellow with brown spots proximally, with slender brown median band, followed by a slender light blue subdistal band and a slender black distal band; caudal fin brown proximally and medially, followed by a slender light blue subdistal band and a slender black distal band; dorsal fin golden with irregular brown blotches and stripes, with narrow light blue subdistal band and narrow black distal band (Ref. 123810). Furthermore, it differs from N. taiti by the morphometric characters of having a smaller head length of 29.5-33.1% of standard length vs. 35.0-38.6%, smaller prepectoral length of 31.2-33.9% of standard length vs. 34.2-38.6%, greater head depth of 81-87% of head length vs. 71-80%, greater interorbital width of 43-49% of head length vs. 31-40%, and greater caudal peduncle length of 145-152% of its depth vs. 134-143% (Ref. 123810).

Description: Relatively small-sized Nothobranchius species; general body shape robust, laterally compressed and deep; greatest body depth at vertical passing through pelvic-fin origin, 28.4-33.8% of standard length; greatest body width at pectoral-fin base with body progressively narrowing towards caudal-fin base; dorsal profile convex from tip of snout to base of last dorsal-fin ray, postdorsal profile straight to slightly concave on caudal peduncle; ventral profile convex from lower jaw to base of last anal-fin ray; postanal profile straight to slightly concave on caudal peduncle from insertion of posteriormost anal-fin ray to caudal-fin base; caudal peduncle shallow, length 1.45-1.52 times of its depth; anus just anterior to anal-fin origin (Ref. 123810). Head moderately long, 29.5-33.1% of standard length, laterally compressed, deeper than wide, head width 66-72% of its depth; snout slightly pointed, smaller than eye diameter; mouth supraterminal, slightly oblique in profile; jaws subequal, lower jaw longer than upper, posterior end of rictus at same level or slightly ventral to centre of eye; premaxilla and dentary with many irregularly distributed conical, slightly curved teeth at outer row of lower and upper jaws; orbit large, 28-32% of head length, mainly in anterior half of head, snout to eye end length 50-54% of head length, at median portion of head side; branchiostegal membrane projecting posteriorly from opercle (Ref. 123810). Dorsal-fin origin anterior to anal-fin origin, both fins originating posterior to mid-length of body; distal border of dorsal and anal fins rounded, with small contact organs in form of papillae on fin rays and distal margin with short filamentous rays; posterior extremity of dorsal fin reaching caudal-fin base; dorsal fin with 16-18 rays; anal fin with 17-19 rays; pectoral fin subtriangular, its insertion slightly posterior to margin of opercular opening; base slightly oblique, upper fin rays placed slightly anteriorly to lower fin rays, tip reaching or slightly surpassing base of pelvic fin; pectoral fin with 18-20 rays; pelvic fin subabdominal, its origin at about mid-length of body, short, bases medially separated, tip reaching urogenital papilla; caudal fin subtruncate, with 17-19 branched rays, plus three or four procurrent rays at dorsal and ventral origins (Ref. 123810). Scales cycloid, body and head entirely scaled, except for ventral surface of head; no scales on dorsal and anal fins; scales in mid-longitudinal series 28-30 plus two or three small scales on caudal-fin base; transverse rows of scales in front of dorsal-fin origin 11; scale rows around caudal peduncle 12 (Ref. 123810). Frontal scalation pattern variable; anterior nostril at anterior tip of snout, tubular opening lateral to upper lip; posterior nostril in front of orbit, with oblique oval aperture; frontal neuromasts arranged in two rows of shallow grooves, one neuromast in each groove; cephalic sensory system at supraorbital level fragmented into two discontinuous portions, in shallow groove with one or two exposed neuromests at anterior level, continued at the posterior supraorbital level with two exposed neuromasts over the orbit, whereas at supratemporal level in slightly curved shallow groove, with four exposed neuromasts; preorbital canal in shallow groove with three exposed neuromasts; postorbital canal in deep groove with one long exposed neuromast, infraorbital level with about ten small buttons or neuromasts at ventral and posterior margin of orbit; preopercular system with exposed neuromasts in deep groove on preopercle portion, whereas in shallow groove with about twelve small buttons on ventral portion; mandibular canal in shallow groove with about ten to twelve small buttons or neuromasts; one neuromast on each scale along trunk mid-longitudinal series (Ref. 123810).

Colouration: Colouration of live male: scales on trunk and head golden-grey with brown scale margins creating irregular vertical stripes on trunk; scales with iridescent light blue on side of body; scales on abdomen light golden to silver; snout and throat grey, dorsal portion of head light brown; posterior scale margins on post-orbital portion of opercle creating three brown oblique bars; exposed branchiostegal membrane grey; iris golden, with dark grey spots on upper and lower parts, creating dark vertical bar through centre of eye; dorsal fin golden with brown spots and brown irregular stripes proximally and medially, and with narrow light blue subdistal band and narrow black distal band; anal fin golden with brown spots proximally, followed by slender brown median band, then broad light blue subdistal band, and broad black distal band; caudal fin brown proximally and medially, with slender light blue subdistal band and slender black distal band; pelvic fin hyaline to brown with broad light blue distal margin; pectoral fin hyaline with light blue posterior distal margin (Ref. 123810). Colouration of live female: scales on trunk and head pale grey-brown, darker on dorsum and lighter to silver on venter; scales with dark grey-brown margin, creating reticulation on trunk and irregular vertical stripes on dorsal and posteroventral portions of flank; light blue iridescence o, trunk and opercular region; iris golden; all fins hyaline (Ref. 123810).