Diagnosis: Nothobranchius sagittae is distinguished from all other members of the Nothobranchius neumanni species group by the following combination of characters: in the male, a relatively elongate body shape, a dorsal profile that is slightly convex, a concave transition between the head and body, a pointed snout, and an upward-directed mouth cleft; the anal fin in the male is red with one or two pale yellow, white or blue-white horizontal bands, a light blue-gray proximal part, and a distinct dark red margin; the caudal fin in the male is usually completely red with a relatively dark marginal band (Ref. 98818).

Description: Nothobranchius sagittae is a Nothobranchius species of moderate size with a pointed snout, upward-directed subterminal mouth, and a protruding lower jaw (Ref. 98818). The dorsal-head profile is slightly concave; the dorsal profile is slightly convex from the nape to the dorsal fin base; the caudal peduncle profile is straight at the upper and lower sides (Ref. 98818). The dorsal fin rays number 15-17, the anal fin rays 15-18, and the relative position of the base of the first anal fin ray is under the base of dorsal fin ray 1 or 2; the pelvic fins are short, not reaching the first anal fin ray; the pectoral fins reach the first pelvic fin ray (Ref. 98818). Scales on the median longitudinal line number 29-32, plus 2 on caudal fin base, most with a shallow pit in the center and one neuromast; the transverse row of scales above the pelvic fins numbers 14, and the scale count around the caudal peduncle is 16 (Ref. 98818). The supra-orbital squamation is variable, but most specimens have G-type, the anterior part being partly covered with epidermal tissue; the central supra-orbital neuromast systems are in two distinct shallow grooves, both sides of each lined with three shallow lobes; the posterior cephalic neuromast systems are in two curved pits (Ref. 98818).

Colouration: Live males: the body is light blue, the abdomen white to pale gray, the back brown-red; posterior margins of the scales are red, forming a reticulated pattern; the snout and lower lip are red, the throat pale blue-gray; the projecting part of the branchiostegal membrane is light gray with a white margin; the caudal fin is red with a narrow dark red margin, and a narrow, discontinuous light gray to pale yellow submarginal band may also be present; the dorsal fin is blue-gray with irregular dark gray-brown to dark gray stripes and spots which become denser and smaller distally; the anal fin is red with one or two pale yellow, white or blue-white horizontal, occasionally irregular, bands; the basal part of the fin is light blue-gray with a variable number of red spots; the pelvic fins are similar to anal fin; pectoral fins are hyaline with pale white-blue posterior margins; the iris is silver (Ref. 98818). Live females: the body colour is pale olive-gray, being darker on the back and lighter on the abdomen; scales on the back and upper parts of the sides have reflective light blue centers; paired and unpaired fins are colourless; the iris is silver (Ref. 98818).