Diagnosis: Labeotropheus rubidorsalis differs from all other Labeotropheus species due to the nuptial colour pattern of the males and by the shape of the anal fin; the males have a vivid, almost metallic, blue head, body, and caudal peduncle, and an equally brilliant red dorsal fin; all other species of Labeotropheus have an angular to kite-shaped anal fin, but L. rubidorsalis has a distinctly rounded anal fin, especially in the posterior portion (Ref. 128773). Labeotropheus rubidorsalis has a generally slenderer body than the most of the robust Labeotropheus, though its range overlaps that of several of these species, 31.6-36.1% of standard length vs. 37.4-40.6% in L. alticodia, 34.3-42.0% in L. artatorostris, 33.8-41.5% in L. aurantinfra, 32.0-38.6% in L. candipygia, 31.9-34.7% in L. chlorosiglos and 35.2-41.5% in L. obscurus; it does have a distinctly slenderer body than some of these species as measured by the distance between the origins of the dorsal and anal fins, 45.6-50.3% of standard length vs. 52.1-53.5% in L. alticodia, 50.2-58.1% in L. artatorostris, 51.3-54.6% in L. chlorosiglos, 52.5-55.5% in L. fuelleborni and 50.8-56.3% in L. obscurus, and the insertion of the dorsal and anal fins, 13.5-15.7% of standard length vs. 16.4-18.1% in L. alticodia, 15.4-18.3% in L. artatorostris, 15.5-16.8% in L. chlorosiglos, 16.5-17.4% in L. fuelleborni and 15.8-17.8% in L. obscurus; it has fewer rows of teeth in the upper jaw, 3-4 vs. 5-8 in L. artatorostris, 4-6 in L. aurantinfra, 4-5 in L. fuelleborni and 4-6 in L. candipygia; it also has fewer rows of teeth in the lower jaw , 3-5 vs. 6 in L. fuelleborni and 5-7 in L. chlorosiglos (Ref. 128773). Labeotropheus rubidorsalis is typically deeper-bodied than the slender-bodied Labeotropheus as indicated by both body depth, 31.6-36.1% of standard length vs. 26.6-33.2% in L. chirangali, 26.3-33.4% in L. trewavasae and 26.9-30.8% in L. simoneae, and by the distance between the origin of the dorsal fin and the attachments of the pelvic fins, 31.5-35.4% of standard length vs. 28.6-33.4% in L. chirangali, 27.1-32.7% in L. trewavasae and 27.5-32.8% in L. simoneae; it also has fewer rows of teeth in the upper jaw than the other slender species, 3-4 vs. 3-6 in L. chirangali, 4-7 in L. simoneae and 5-7 in L. trewavasae; it also has fewer rows of teeth in the lower jaw than L. trewavasae, 3-5 vs. 5-6 (Ref. 128773).

Description: Body compressiform with flattened ovoid shape; body consistently deep throughout its length, especially for a slender Labeotropheus; body wide, almost cylindrical in transverse cross section (Ref. 128773). Scales on belly and anterior abdomen cycloid and tightly crowded; flank scales ctenoid; exposed portion of scale fan-shaped and approximately hexagonal; anterior lateral line overlapping posterior lateral line by 0-3 scales; anterior lateral line scales 22-25, posterior lateral line scales 11-13; dorso-lateral scale rows 8-10, pectoro-pelvic scale rows 10-11 (Ref. 128773). Dorsal fin long, 56.0-62.6% of standard length, with 17-19 spines and 7-8 rays; origin of dorsal fin posterior to or overlapping opercular tab; dorsal-fin rays 3, 4, 5 long, reaching to hypural and beyond to caudal fin; anal fin rounded posteriorly in all specimens; origin of anal fin opposite dorsal-fin spine 14, 15, or 16; insertion of anal fin anterior to insertion of dorsal fin; anal-fin rays 3, 4, 5 reach past hypural in males, only reach to mid-cauadal peduncle in females; caudal fin subtruncate; pectoral fin long and rounded, with 13-15 rays; pelvic fin long, minimally reaching origin of anal fin and longer in the majority of specimens; pelvic-fin ray slightly produced and filamentous in half of specimens, non-filamentous in other half; pelvic-fin attachment opposite dorsal-fin spine 4, 5, or 6 (Ref. 128773). Head long and deep, especially for a slender-bodied Labeotropheus; head depth 91.6-105.0% of head length; head profile moderately curved with no concavity above eye; snout long and wide with slightly protruding snout; snout pad 10.3-14.2% of head length; cheek with 3-4 scale rows; infraorbital pores 7-9, with 8-25 neuromasts distributed among them; oral jaws long and wide; oral teeth tricuspid and closely set on upper and lower jaws; 5-12 tricuspid teeth on lateral portion of left upper jaw (Ref. 128773). Gill rakers stout, triangular, and widely spaced; 5-8 ceratobranchial and 2-3 epibranchial gill rakers on first gill arch; all specimens with 1 raker between the cerato- and epibranchial rakers (Ref. 128773).

Colouration: Colouration of males: head, operculum, flank, caudal peduncle brilliant, solid blue; 11 faint bars spanning flank and caudal peduncle; opercular tab faint metallic green; dorsal fin brilliant red, fading somewhat posteriorly; small hyaline spots in rayed dorsal fin; caudal fin same brilliant blue as rest of body, fading posteriorly, with thin red trailing edge; spinous portion of anal fin white, becoming blue in rayed portion; 3-5 yellow eggspots present; pelvic fin bluish white posteriorly with white leading edge, pale red between (Ref. 128773). Colouration of females: females with orange blotch colour pattern across entire body and all fins; ground colour is pale orange with black, white, and darker orange spots of irregular shape and varying size; opercular tab black or black with faint green sheen; anal fin hyaline in some individuals, some individuals with faint orange blotches overlying hyaline anal-fin membrane; all individuals with 1-7 very small orange eggspots present on anal fin (Ref. 128773). In preservative, males uniformly grey with 11 bars faintly visible across flank and caudal peduncle; females uniformly white or pale grey with dark grey and/or black spots across flank and caudal peduncle (Ref. 128773).