Diagnosis: Pseudocrenilabrus pyrrhocaudalis can be differentiated from the other species of the genus Pseudocrenilabrus on the basis of its colour pattern and its subtruncate caudal fin (Ref. 114630). Male P. pyrrhocaudalis have a unique colour pattern characterized by some orange colour on their anal and caudal fins that can become bright orange-red in breeding males, extending over the proximal parts of the anal and caudal fins and the distal part of the caudal and the upper and lower parts of the caudal peduncle (Ref. 114630). In addition, P. pyrrhocaudalis can be distinguished from its sympatric congener P. philander by a combination of the following characters: pelvic fin white, vs. black; posterior part of dorsal fin orange, vs. olive green in the other species; comparatively thinner lips, vs. comparatively thicker lips; larger eye diameter 27.0–39.3% of head length, vs. 22.9–33.1%; narrower head width 37.0–47.3% of head length, vs. 38.5–53.7%; narrower interorbital distance 14.6–22.3% of head length, vs. 20.5 29.4%; and a more slender caudal peduncle 8.8-11.8% of standard length, vs. 11.3–13.9%, and 50.0–64.7% of caudal peduncle length, vs. 64.3–93.5% (Ref. 114630).

Description: In both sexes: body relatively deep, head profile somewhat convex, mouth inclined upwards with relatively thin lips, interorbital distance narrow, caudal fin sub-truncate (Ref. 114630). Lower pharyngeal bone relatively slender and slightly longer than wide; pharyngeal teeth all fine; those of the posterior row clearly larger than the others; teeth of the two median rows somewhat enlarged; there is a small gradient in the orientation of the major cusp of the pharyngeal teeth from slightly backwards on the anterior parts of the pharyngeal jaw towards more erect posteriorly and slightly forward in the posteriormost rows (Ref. 114630). Scales in upper lateral line 17-23; scales in lower lateral line 8-13; longitudinal line scales 28-33; transverse scales below lateral line 5-8; scales between pectoral and ventral fins 3-5; scales around caudal peduncle 12; cheek scales 3-4 (Ref. 114630).

Colouration: Breeding males with a bright orange colourationon caudal and anal fins; an orange spot on the anal fin, distal parts of caudal and anal fins white; base of the caudal fin bright orange more than 2/3 of fin; head and upper lateral part of body grey, while the lower part yellowish orange; dorsal fin with white lateral dots arranged as stripes radiating from base to tips of dorsal-fin rays; pelvic fins bright white (Ref. 114630). Females generally grey, with no anal-fin spot; pelvic fins bright white; bright orange lower half of caudal; some orange flashes at base of caudal and anal fins; some spots and streaks on dorsal and caudal fins (Ref. 114630).