Diagnosis: Nothobranchius vosseleri is a member of a group of Nothobranchius species of relatively large size and with a slender body, less than 30% of standard length, compared to other species of the genus; and a distinct red caudal fin in male (Ref. 96650). It can be distinguished from other species of the so-called N. melanospilus group by a pointed snout, and the presence of a dark vertical bar through the iris (Ref. 96650).

Description: Nothobranchius of medium size with distinctly pointed snout; mouth wide, directed upward (Ref. 96650). Dorsal-fin origin above or just behind origin of anal fin and behind mid-length of body; dorsal fin with 14-16 rays, anal fin with 15-18 rays (Ref. 96650). Scales on mid-longitudinal line 25-31+3-4 on caudal fin, most with a shallow pit in center, not connected to an underlying neuromast system; transverse rows of scales above pelvic fins 10-11; transverse rows of scales on caudal peduncle 6-7 (Ref. 96650). Anterior and central supraorbital neuromast systems separated and consisting of two shallow grooves, lined with low lobes; cephalic squamation irregular, not representing any pattern, and anteriorly covered by epidermal tissue; posterior supraorbital neuromast systems strongly curved, but less than 90; preopercular neuromast system in an open groove, distal end not overlapping operculum (Ref. 96650).