Papiliolebias ashleyae is distinguished from all other congeners by the following characters: lower prepelvic length in males 43.6-44.7% SL (vs. 44.9- 51.5% SL); lower pre-pelvic length in females 43.3-46.8% SL (vs. 48.2-51.7% SL); and color pattern of males consisting of an overall redbrownish coloration, including the dorsal, caudal and pelvic fins basis (vs. overall color pattern dark blue, but never red-brown). Additional characters useful to distinguished from other species include a reddishbrown stripe on the basis of the dorsal and anal fins, with whitish blotches, and distal portion of anal- and caudal-fins bluish (vs. absence of reddish- brown stripe in the remaining species of the genus, where the caudal and anal-fin basis possess white and black spots); dorsal-fin origin at vertical through base of anal-fin rays 9th-10th (vs. 7th-8th in P. bitteri and 6th-9th in P. hatinne); body with brownish-red background and iridescent greenishblue scales, forming slender, oblique, ladder-like stripes (vs. oblique thick lines arranged parallel to each other); pelvic-fin red, with three spots (from basal to distal portion of fin): white, dark red and white (vs. dark blue without spots); third pelvic fin-rays transformed into a filament (vs. third pelvic-fin ray not transformed into a filament), and pelvic-fin separated by a small 4 mm interspace (vs. not separated) (Ref. 94790).