Diagnosis: Nimbapanchax maeseni, N. melanopterygius, N. viridis and N. jeanpoli are distinguished from N. petersi and Aphyosemion guineense by a white or light blue margin around caudal fin, not always completely closed, a small dark brown or reddish submarginal stripe and brown blotches between fin rays, no yellow zone in fins, females without or with small spaced dark bars on side versus an often broad yellow to yellow-greenish or whitish marginal or submarginal zone on anal and lower caudal fin, females on side with wide spaced dark bars in N. petersi and an asymmetrically coloured caudal with white upper and lower margin, a dark brown or red submarginal line and alternating white and brown or red streaks from center to posterior fin margin, sometimes fin center blue-greenish and alternating pattern only in posterior caudal fin in Aphyosemion guineense (Ref. 82704). Nimbapanchax maeseni, N. melanopterygius, N. petersi, N. viridis and Aphyosemion guineense are distinguished from N. jeanpoli by the lack of broad brown or red-brown vertical bars or blotches on side in males; N. maeseni and N. melanopterygius can be distinguished from N. viridis and N. jeanpoli by brown sides of males with center of many scales metallic blue-green, only little red pigmentation on head and sides and a dark brown or red blotch above and slightly posterior to the insertion of pectoral fin on side in females versus blue-green scales with only narrow brown scale margins on the side of males with distinct red dots forming lines or horizontal stripes in N. viridis or the before mentioned brown or red-brown vertical bars or blotches on upper half of side in N. jeanpoli, and no dark blotch above insertion of pectoral fin in females (Ref. 82704). It is distinguished from N. melanopterygius by a white or light blue margin and a dark brown or red submarginal band in the anal fin and a blue-green center in unpaired fins with small dark brown or red dots versus a black, dark brown, or dark red marginal, sometimes white submarginal band in anal fin and a less dense pattern of brown or dark red blotches in anal and caudal fin in N. melanopterygius (Ref. 82704). Nimbapanchax maeseni is distinguished from Aphyosemion guineense, N. melanopterygius, N. jeanpoli and N. viridis by a pattern of vertical stripes on sides formed by metallic blue-greenish scales in young males and a similar pattern of brown stripes in females versus absence of vertical striped pattern or broad, dark brown stripes or blotches on upper half in N. jeanpoli, and vertical stripes only faint in frightened females of N. melanopterygius (Ref. 82704).

Description: A cylindrical, laterally slightly compressed and elongate medium sized nothobranchiid species; dorsal profile straight on head, slightly convex from nape to caudal peduncle, greatest body depth approximately at base of pelvic fin; ventral profile slightly convex from head to end of anal fin base, caudal peduncle slightly concave (Ref. 82704). Snout slightly pointed, mouth directed upwards, lower jaw longer than upper, posterior end of rictus at same level as or slightly above center of eye (Ref. 82704). The opercle borders on the ventral side have their smallest distance at or slightly posterior of the eye level and then widen anteriorly on the lower jaw (Ref. 82704). Closed frontal neuromast system with one groove, preopercular neuromast system with 5 pores (Ref. 82704). Total number of vertebrae 29-30, number of vertebrae with pleural ribs 14, with haemal spines 15-16 (Ref. 82704). Dorsal and anal fins in males slightly pointed; caudal fin rounded, no filamentous extensions; fins in females generally smaller and more rounded; basal part of fins covered with an opaque mucus film; dorsal and anal fins located posterior to mid-body; first dorsal fin ray behind origin of anal fin, situated above anal fin ray 6 to 8; dorsal fin rays 10-14; anal fin rays 14-18; pectoral fin extending posteriorly, not reaching origin of pelvic fin; pelvic fin not or just reaching anal fin; pectoral fin rounded (Ref. 82704, 126460). Scales cycloid; body and head entirely scaled, except for ventral surface of head; frontal squamation of G-type; scales on lateral line 28-30 and 3-4 on caudal fin base, not all scales with small grooves in center; transverse rows of scales above pelvic fin 9-10; circumpeduncular scale row 13-14 (Ref. 82704). The epineural ribs are distinctly bifid as for other members of the tribe Callopanchacini; the neural process of the second vertebra is distinctly wider than the neural processes of adjacent vertebrae and possessing a fan-shaped morphology; the neural processes of vertebrae 4-5 are narrow and long, as for all nothobranchiids, except species of Epiplatys (Ref. 126460).

Colouration: Colouration of preserved specimen: brownish pattern with a white band on both the dorsal and anal fins; males with side and back dark grey or brown, belly lighter brown, scale borders dark, forming a reticulated pattern, unpaired and pelvic fins greyish dark with whitish margin, pectoral fins pale dark grey, paler on margin; females are similar to males and same as juveniles, with dark vertical bars on sides, fins dark grey, unpaired fins with white margin, paired fins with pale grey margin (Ref. 82704, 126460). Colouration of live males: dark red and metallic blue reticulations on the body sides, a typical dark red patch is present behind the origin of the pectoral fins, the anal and caudal fins display a metallic blue band (Ref. 126460); sides dark brown, some scales in center blue-green or copper, in young males a vertical pattern of metallic blue-green and brown bars, in older males scales with brown margin and blue-green center forming reticulated pattern; back brown, belly greyish to light brown; head brown, scales with dark brown margin, on opercle and slightly posterior red pigments on scales, above or slightly posterior to insertion of pectoral fin daek brown or red blotch; ventral side of head dark grey or grey-brown; unpaired fins in center blue-green with more or less regular brown dots or stripes, white or light blue fin margins, dark submarginal zone; pelvic fins similarly coloured as anal fin, pectoral fins hyaline with whitish to blue-greenish margin (Ref. 82704). Colouration of live females: a colour pattern much less characteristic is visible on the body sides with dark crossbars and a faint dark red-bluish reticulation; sides brown, center of scales often light brown, dark scale margin, forming a reticulated pattern; behind opercle, above and slightly posterior to insertion of pectoral fin a dark brown or red blotch, followed posteriorly by dark brown bars; back brown, belly light brown; unpaired fin in center blue-green or greenish with dark dots between fin rays, with faint whitish margin and submarginal dark zone; pelvic fins similarly coloured as anal fin, pectoral fins hyaline (Ref. 82704, 126460).