Diagnosis: Nothobranchius taeniopygus is distinguished from all other species of the genus by the following combination of characters in males: body colouration light blue with red-brown scale margins; anal fin light blue-grey to yellow-grey with irregular brown spots, narrow brown submedial band, slender cream to yellow medial band, narrow yellow to white subdistal band and a broad black distal band; caudal fin light yellow-grey with brown stripes proximally, followed by a narrow brown medial band, a slender white subdistal band and a broad black distal band; pelvic fins brown, with slender cream to yellow medial band and narrow black distal band (Ref. 122068). Furthermore, it differs from the other members of the Nothobranchius taeniopygus species group in central and western Tanzania by a postorbital length of 43-46% of head length vs. 46-63%; and snout to eye end length 54-57% of head length vs. 37-54% (Ref. 122068).

Description: General body shape robust, laterally compressed and deep; greatest body depth at vertical in front of pelvic-fin origin, 30.-35.1% of standard length; greatest body width at pectoral-fin base with body progressively narrowing towards caudal-fin base (Ref. 122068). Dorsal profile convex from tip of snout to base of last dorsal-fin ray, straight to slightly concave on caudal peduncle; ventral profile convex from lower jaw to base of last anal-fin ray, straight to slightly concave on caudal peduncle; caudal peduncle relatively deep, length 1.4-1.5 times its depth; anus situated directly in front of anal-fin origin (Ref. 122068). Head modestly long, 29.6-32.7% of standard length, laterally compressed, deeper than wide, head width 65-72% 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, 26-29% of head length, mainly in anterior half of head, snout to eye end length 54-57% of head length, in dorsal portion of head side; branchiostegal membrane projecting posteriorly from opercle (Ref. 122068). Dorsal-fin origin slightly anterior to anal-fin origin, both fins originating posterior to mid-length of body; extremity of dorsal and anal fins rounded, with small contact organs in form of papillae on fin rays and distal margin with short filamentous ray; posterior extremity of dorsal fin reaching caudal-fin base; dorsal-fin 15-17 rays; anal fin 16-18 rays; pectoral fin subtriangular, 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 overlapping base of pelvic fin; pelvic fin subabdominal, origin slightly in front of mid-length of body, short, bases medially separated, tip reaching urogenital papilla; caudal fin subtruncate, with 18-20 branched rays, plus 2 or 3 dorsal and ventral procurrent rays (Ref. 122068). 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 29-31 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 12-14 (Ref. 122068). Cephalic squamation pattern variable; frontal neuromasts separate in two rows of shallow grooves behind the upper lip, with one or two neuromasts in each groove; cephalic sensory system at supraorbital level in undivided shallow groove with five exposed neuromasts, whereas at supratemporal level with four exposed neuromasts in undivided, curved shallow groove; preorbital canal in shallow groove with four exposed neuromasts; infraorbital level with series of about 20 small buttons at ventral and posterior margin of orbit; postorbital canal in deep groove with one exposed neuromast; preopercular system with exposed neuromasts in deep groove; mandibular canal in shallow groove with about ten small buttons; one neuromast on each scale along trunk mid-longitudinal series (Ref. 122068).

Colouration: Live male: scales on trunk and head light iridescent light blue to blue-green with broad dark red-brown margins, forming a regular reticulation pattern; scales on abdomen faint blue to white with less pronounced margins; scales on dorsal part of the back, anterior to the dorsal fin, with wider margins lending an overall darker appearance; snout, frontal and dorsal portions of head light blue to grey; throat pale blue; exposed part of branchiostegal membrane white to cream; iris golden; dorsal fin yellow-brown with irregular red-brown spots and vermicular patches in proximal zone grading distally to streaks parallel to fin rays, becoming finer distally; small, elongate black mark sometimes present on membrane between first two anterior fin rays; basal zone of anal fin light blue to yellow with irregular red-brown spots in proximal zone that may be crudely aligned parallel to the base; followed by a narrow, irregular red-brown submedial band broader posteriorly than anteriorly; a moderately broad to slender, cream to yellow medial band that may taper posteriorly; followed transitionally by a narrow yellow, cream or white subdistal band and a broad black distal zone; base and proximal part of the caudal fin light blue-grey to yellow grey, with dark brown to red-brown radiating stripes parallel to fin rays in the latter zone; arcuate pattern in posterior part of fin comprises a narrow, dark red-brown medial band, followed distally by a slender white band and a broad black marginal zone; pelvic fins mimic, in part, pattern of anal fin with narrow light blue to yellow-grey basal zone, followed by a slender cream to yellow medial band with submedial red-brown markings, and narrow black distal component; pectoral fins dominantly hyaline with light blue margins (Ref. 122068). Live female: trunk and head light grey-brown, darker on dorsum and lighter ventrally; scales with a very narrow grey margin; scale centres iridescent silver to very pale blue; all fins hyaline; iris golden (Ref. 122068).