Diagnosis: All diagnostic characteristics of Labeotropheus are present, including a steeply sloping head; broad, fleshy snout; wide jaws with retrognathous lower jaw; and an interior and subterminal mouth (Ref. 116021). Labeotropheus artatorostris differs from the slender-bodied Labeotropheus, L. trewavasae and L. simoneae, by its deeper body depth, 34.3-42.0% of standard length vs. 26.9-30.8% in L. simoneae and 25.3-33.4% in L. trewavasae; greater distance between insertion of dorsal fin and origin of anal fin, 29.2-34.0% of standard length vs. 27.4-28.6% in L. simoneae and 26.3-29.1% in L. trewavasae; and greater distance between origin of dorsal fin and insertion of pelvic fins, 36.1-41.1% of standard length vs. 27.5-32.8% in L. simoneae and 26.1-32.7% in L. trewavasae (Ref. 116021). Labeotropheus artatorostris is different from L. curvirostris by having more teeth rows in both the upper and lower jaws, 5-8 vs. 3 and 3-8 vs. 1, respectively; more infraorbital neuromasts, 12-36 vs. 9; shorter upper jaw, 15.6-22.9% of head length vs. 23.6%; and a narrower snout, 33.2-40.2% of head length vs. 42.6% (Ref. 116021). It differs from L. fuelleborni due to a shorter snout pad, 7.43-14.2% of head length vs. 14.9-17.2% in L. fuelleborni and 9.0-17.2% in types of L. fuelleborni and Messule specimens; more rows of teeth in the upper jaw, 5-8 vs. 4-5 in L. fuelleborni types and Messule specimens; and more gillrakers on the first ceratobranchial, 7-10 vs. 7-8 in L. fuelleborni (Ref. 116021). It differs from L. chlorosiglos due to greater distance between the opercular tabs, 16.6-18.7% of standard length vs. 14.7-15.7% in L. chlorosiglos; and greater distance between origin of dorsal fin and insertion of pelvic fin, 36.1-41.1% of standard length vs. 33.0-36.0% in L. chlorosiglos (Ref. 116021). Labeotropheus artatorostris also has longer pectoral fins, 24.6-33.3% of standard length, than all other species of Labeotropheus: 22.2-26.0% in L. chlorosiglos, 23.1-25.7% in L. fuelleborni, 22.2-29.3% in L. fuelleborni types and Messule specimens, 21.9-26.3% in L. simoneae, and 18.4-23.9% in L. trewavasae; it has also a wider body than all other species of Labeotropheus, body width at pectoral fins 14.0-18.3% of standard length vs. 12.7-14.3% in L. chlorosiglos, 15.0-16.9% in L. fuelleborni, 13.1-17.9% in L. fuelleborni types and Messule specimens, 13.0-15.6% in L. simoneae, and 12.1-16.6% in L. trewavasae; body width at opercular tabs 16.6-18.7% of standard length vs. 14.7-15.7% in L. chlorosiglos, 16.2-18.2% in L. fuelleborni, 15.3-18.4% in L. fuelleborni types and Messule specimens, 14.7-16.7% in L. simoneae, and 12.1-16.6% in L. trewavasae (Ref. 116021). Finally, L. artatorostris differs from all other species of Labeotropheus based on fin colouration of males: presence of orange-red pigmentation in pelvic, anal, and rayed dorsal fins in L. artatorostris vs. all fins blue in L. fuelleborni and L. trewavasae, and whitish-blue anal and yellow-rayed dorsal fins in L. chlorosiglos and L. simoneae; Labeotropheus artatorostris also lacks the large orange flank patch found in L. chlorosiglos and L. simoneae, and the orange pigmentation present on operculum of L. simoneae (Ref. 116021).

Description: Body depth 34.3-42.0% of standard length, and distance between dorsal-fin insertion and anal-fin insertion 15.4-18.3% of standard length; body wide, width at opercular tabs 16.6-18.7% of head length and width at pectoral fins 14.0-18.3% of head length (Ref. 116021). Head long, head length 29.9-34.9% of standard length, and relatively deep, head depth 93.6-114.8% of head length; cheek with 2-5 scale rows; snout relatively long but narrow; snout length 25.2-40.8% of head length, snout width 33.3-40.2% of head length; snout pad short, 7.4-14.2% of head length (Ref. 116021). Oral jaws compact; lower jaws long but narrow, 23.7-39.3% of head length and 39.0-48.1% of head length, respectively; but lateral length of mandible relatively long, 15.6-22.9% of head length; upper jaw with 5-8 rows of teeth, and 4-10 teeth on lateral portion of left upper jaw; lower jaw 3-8 rows of teeth, and 19-35 teeth present in left half of first row of lower jaw (Ref. 116021). Gill rakers stout, triangular, and widely spaced; 7-10 on ceratobranchial and 1-4 epibranchial gill rakers on first gill arch; all specimens with 1 raker between the cerato- and epibranchial rakers; 9-13 total gill rakers (Ref. 116021). Dorsal fin 56.2-64.5% of standard length, with 15-18 spines and 8-9 rays; pectoral fins long, 24.6-33.3% of standard length, rounded, with 12-15 rays; pelvic fins long, especially in mature males, reaching anal-fin origin and sometimes beyond, with 6 rays; anal fin with 3 spines and 6-8 rays (Ref. 116021). Anterior lateral line with 21-24 scales, posterior lateral line with 9-16 scales, and 0-6 scales overlapping between the anterior and posterior lateral lines (Ref. 116021).

Colouration: Colouration of living males from Thumbi West Island: body and head blue; dorsal fin blue with orange trailing edge and yellow ocelli, but less black in the rayed portion than Monkey Bay form; anal fin blue at base, otherwise orange-pink with 3-8 yellow egg-dummies; pelvic fins mainly orange with narrow black submarginal bands and whitish-blue leading edges (Ref. 116021). Colouration of living males from Mumbo Island: body and head dark blue; dorsal fin pale blue with orange-red rayed region; caudal fin rays blue with orange inter-ray membranes and yellow trailing edge; anal fin orange with yellow egg-dummies; pelvic fins orange-red with light blue leading edges (Ref. 116021). In preservative, males uniform brown; eleven vertical bars on caudal peduncle and flank visible on some specimens (Ref. 116021). Colouration of living females from Mumbo Island: dark blue-grey and orange-blotch, but the orange-blotch form is rare (Ref. 116021). In preservative, females uniform brown; eleven vertical bars on caudal peduncle and flank visible on some specimens (Ref. 116021).