Xenurolebias cricarensis can be diagnosed from X. myersi and X. pataxo by having dark reddish brown bars on the caudal fin slightly contrasting with lighter interspaces in males (vs. strongly contrasting); from X. izecksohni in having a deeper head in males (head depth 85.6-92.8% of head length vs. 81.2-85.0%), a longer lower jaw in males (22.0-25.0% of head length vs. 18.6-20.9%), a deeper body in larger males (above 31 mm SL) (body depth 30.7-33.9% SL, vs. 27.1-27.5% SL), and dorsal and anal-fin filaments reaching between the base and middle of the caudal fin in males (vs. reaching posterior portion of the caudal fin). It can be further distinguished from X. myersi by having the caudal fin lanceolate in larger males, with a pronounced posterior tip (vs. sub-lanceolate, never forming a distinctive tip posteriorly) and more dark brown bars on the caudal fin in males (7-10 vs. 4-6); and from X. pataxo by having 1-5 black spots on the posterior part of the caudal peduncle in females (vs. absence) (Ref. 96072).

Description: Dorsal fin with 16-18 rays in males, 14-17 rays in females; anal fin with 21-23 rays in males, 20-23 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; in males, 2-3 filamentous rays on tip of dorsal and anal fins reaching vertical through posterior portion of caudal fin; most dorsal-fin rays branched, rays on fin tip unbranched; and caudal fin lanceolate with pointed extension often bearing two short filamentous rays (Ref. 96072).