Discordipinna filamentosa can be distinguished from D. griessingeri by the following unique set of features: D VI (vs. V), first dorsal fin with the longest, filamentous first ray in male extending far beyond caudal fin base when depressed (vs. second ray of dorsal-fin base longest in male); pectoral fin rays 16 (vs. 17-20); longitudinal scale rows 26; predorsal naked; transverse scale rows 8; dorsal pterygiophore formulae 3/122101/9 (vs. 3/41001/8); vertebrae 10 + 16 = 26; with loosely arranged, longitudinal pattern of infraorbital papilla and anterior oculoscapular canal present (with median pore ? singular on middle of interorbital region, lateral section as pores ?, ? and ?) and preopercular canal (with three pores ?, ? and ?), lacking posterior oculoscapular canal; body generally creamy white; head with a snow-white oblique band from upper lip to upper part of opercle; scattered tiny, densely-set tiny orange to brown spots on dorsal side of snout; 3 lateral, oblique orange to brown bands which generally fused ventrally on trunk; lateral body with 4-5 thin longitudinal yellow stripes; first dorsal fin yellow with 12 major transverse deep brown bands mainly on filamentous portion of the fin (vs. entirely orange red) and an oval translucent mark on basal portion of that; second dorsal fin yellow with about 4 rounded gray blotches each having a central deep black spot against yellow background; caudal fin yellow with a shallow 'C' shaped snow white mark basally and several round deep black spots on upper half; anal and pelvic fins are entirely deep black (vs. with lower 2/3 region orange red and upper 1/3 region translucent); pectoral fin with a snow-white wedge (Ref. 90871).