Xenurolebias izecksohni is distinguished from all other species of Xenurolebias by lacking light spots on the distal half of the dorsal fin in males (vs. presence) and having oblique short bars on the ventral portion of the caudal fin in males (vs. absence). It also differs from X. myersi by having the caudal fin lanceolate in males, with a pronounced posterior tip (vs. sub-lanceolate, never forming a distinctive tip posteriorly), more dark grey bars on the flank in females (12-13 vs. 9-11), a more slender body (body depth 27.1-28.5% SL in males and 28.5-30.6% in females, vs. 29.0-31.4% and 30.1-33.9%), and a shorter lower jaw (18.6-20.9% of head length in males and 17.7-19.7% in females, vs. 22.4-24.5% and 19.6-21.4%, respectively); from X. pataxo by the possession of two or three black spots on the posterior part of the caudal peduncle in females (vs. absence); and from X. cricarensis by having a more slender head in males (head depth 81.2-85.0% of head length vs. 85.6-92.8%), a shorter lower jaw in males (18.6-20.9% of head length vs. 22.0-25.0%) and a more slender body in larger males (above 31 mm SL) (body depth 27.1-27.5% SL, vs. 30.7-33.9% SL) (Ref. 96072).

Description: Dorsal fin with 16-18 rays in males, 13-15 rays in females; anal fin with 21-23 rays in males, 19-21 rays in females; extremity of dorsal fin pointed and long in males, rounded to slightly pointed in females; tip of anal fin pointed in males, rounded in females; caudal fin lanceolate with pointed extension often bearing two short filamentous rays (Ref. 96072).