Diagnosis: Distinguished from its congeners by the following characters: presence of black pectoral and anal fins, with dark chromatophores extending to the distal tips of the fin rays, and from all congeners (except R. lundbergi) by long pectoral fins (P1/HL = 127.7 ±13.4 vs. 60-100); except with R. lundbergi, the anterodorsal margin of the opercle forms a sharp right (vs. sloping obtuse) angle; except R. lundbergi, it has a sickleshaped maxilla with concave dorsal margin (vs. broad maxilla with straight dorsal margin); infraorbital canal bones five and six ossified as complete slender tubes (vs. broad partial cylinders with bony arches); sphenotic spine ventral to infraorbital portion on frontal (vs. posterior to infraorbital portion on frontal); posttemporal fossa absent (vs. present); opercle with anterodorsal facet; cleithral process narrow (vs. broad); cleithrum with a semi-lunar margin against the base of the pectoral-fin radials, a long pectoral-fin (longer than head length vs. shorter); displaced hemal spines 3-4 (vs. 2); and pectoral-fin with black chromatophores on rays (vs. hyaline rays). Rhabdolichops nigrimans can further be distinguished from

R. lundbergi by having: a longer body (maximum total length 419 vs. 233 mm TL; n = 15 for each species); an exaggeratedly scaly appearance of anterior epaxial body surface due to chromatophores concentrated along outer scale margins; larger teeth on premaxilla, mesopterygoid and dentary; and more numerous teeth on premaxilla (20-25 vs. 18-20), mesopterygoid (11-13 vs. 8), and dentary (25-34 vs. 12-13; n = 2 adults for each species); and sexual dimorphism of the caudal appendage (tail) length in which mature males possess a longer caudal appendage than mature females (mean CA 44 ± 2.9% vs. 38 ± 3.2%; n = 5 each) (Ref. 55969).