Diagnosis: Ancharius griseus is distinguished from A. fuscus in having a longer dorsal-fin spine, 22.9-24.3% of standard length vs. 14.6-22.6%; longer snout, 49.2-51.3% of head length vs. 40.1-45.8%; smaller eye, 9.3-10.1% of head length vs. 11.4-15.4%; and pectoral spine serrated posteriorly along only its distal half vs. entire length (Ref. 56142).

Description: Body cylindrical, becoming more laterally compressed toward caudal peduncle (Ref. 56142). Dorsal profile gently convex from dorsal-spine base to anterior orbital margin, nearly straight anterior of orbit; dorsal profile horizontal from dorsal-fin origin to middle of adipose-fin base, then sloping gently ventrally to end of caudal peduncle; ventral profile almost horizontal to anal-fin base, then sloping gently dorsally to end of caudal peduncle (Ref. 56142). Head moderately depressed, dorsal profile slightly convex and ventral profile almost straight (Ref. 56142). Bony elements of dorsal surface of head covered with thick skin, although granular surface of neurocranium faintly visible in inter- and postorbital region; supraoccipital spine short and broad, with gently converging sides and blunt tip; in contact with anterior nuchal plate (Ref. 56142). Eye ovoid, horizontal axis longest, with free margin; located entirely in dorsal half of head (Ref. 56142). Gill openings wide, extending from ventral to posttemporal region to isthmus at vertical through anterior orbital margin; gill membranes broadly fused to each other and attached to isthmus, save for narrow flap along posterior margin at isthmus; gently notched at ventral midline (Ref. 56142). Snout not strongly produced, with convex triangular profile in lateral view; mouth subterminal; oral teeth small and unicuspid, in irregular rows on all tooth-bearing surfaces; premaxillary tooth band broad and crescentic, of equal width throughout; premaxillary teeth conical; dentary tooth band in two semicrescentic patches, separated at midline; much narrower than premaxillary tooth band at symphysis; dentary teeth recurved (Ref. 56142). Barbels in three pairs; maxillary barbel short, thick and flattened, extending four fifths of distance between its base and base of pectoral spine, with membranous extension of uniform width along entire posterior margin of barbel; inner mandibular-barbel origin proximal to midline, barbel thick and flat, extending to vertical through anterior orbital margin; outer mandibular barbel originating posterolateral to inner mandibular barbel, thick and flat, and extending to two thirds of distance between its base and base of pectoral spine (Ref. 56142). Skin smooth; lateral line complete; canal running along lateral myoseptum, with pores emanating from short ventrally and dorsally directed oblique branches (Ref. 56142). Dorsal fin with spinelet, spine and 6-7 rays; dorsal-fin origin anterior to mid-body, at about two-fifths of body length; dorsal-fin margin straight, with first branched fin ray not significantly longer than others; dorsal-fin spine long, straight and slender, adpressed spine overlapping anterior fifth of adipose fin; anterior margin of spine with asperities on proximal two thirds; posterior margin smooth; anterior nuchal plate rectangular, closely sutured to supraoccipital process; median nuchal plate with truncate anterior tip (Ref. 56142). Pectoral fin with stout spine, sharply pointed at tip and 8 rays; anterior spine margin with 10-21 shallow, anteriorly-directed serrations along entire length; posterior spine margin with 15-23 weak, retrorse serrations along distal half of spine; pectoral fin triangular, with straight anterior and posterior margins; humeral process short and slender, with concave dorsal edge and extending to middle of anterior nuchal plate (Ref. 56142). Pelvic-fin origin at vertical through midpoint between posterior margin of dorsal-fin base and adipose-fin origin, with i,5 rays and slightly convex margin; tip of adpressed fin not reaching anal-fin origin; anus and urogenital openings located at vertical through midpoint of adpressed pelvic fin (Ref. 56142). Adipose fin with convex margin for entire length; deeply incised posteriorly; length of adipose base approximately 1.5 times length of anal fin base (Ref. 56142). Anal-fin origin located at vertical through anterior half of adipose fin; fin with v,10 rays and straight posterior margin (Ref. 56142). Caudal peduncle deep; caudal fin moderately forked, with i,6,7,i principal rays; upper and lower caudal lobes broad, pointed distally; upper lobe longer than lower; procurrent rays extending only slightly anterior to fin base (Ref. 56142).

Colouration: Ground coloration in ethanol lead gray on dorsal and lateral surfaces of head and body, fading to light gray on ventral surfaces; small, darker spots randomly and sparsely distributed on dorsal and lateral surfaces of head and body; adipose fin, and fin rays and membranes of median fins, lead gray; paired fins with similar lead gray coloration as body dorsally, light gray ventrally; maxillary barbels lead gray dorsally, light gray ventrally (Ref. 56142).