Diagnosis: Chiloglanis mongoensis is readily distinguished from all other valid species of Chiloglanis with the exception of C. marlieri and C. harbinger in possessing 28-30 mandibular teeth in one row (Ref. 120898). Chiloglanis mongoensis is distinguished from C. marlieri in possessing a longer dorsal spine, 1.8 times into head length versus 3.1 in C. marlieri (Ref. 12898). It is distinguished from C. harbinger in having fewer premaxillary teeth, 99-116 versus 150-224, arranged in fewer rows, 4-5 versus 7; a longer dorsal spine, 9.0-9.7% of standard length versus 7.8-9.0%; a deeper body at anus, 14.0-16.0% of standard length versus 11.7-13.8%; a larger eye, 3.7-4.6% of standard length versus 2.9-3.5%; and a higher adipose fin, 2.6-3.9% of standard length versus 1.6-2.3% (Ref. 120898).
Description: A moderate to diminutive Chiloglanis; body dorsally depressed anteriorly, laterally compressed posteriorly; pre-dorsal convex, sloping ventrally towards posterior nares; pre-orbital convex, sloping ventrally sharply anterior of nares; post-dorsal body gradually sloping towards the caudal fin; pre-anal profile largely horizontal to convex; post-anal profile concave (Ref. 120898). Small unculiferous tubercles present on body; concentrations higher near head (Ref. 120898). Head depressed; gill membranes broadly united; gill openings restricted, opening near horizontal level of pectoral-fin terminus to level of orbit; occipital-nuchal shield covered and visible through skin; eyes moderate, located just posterior to mid-head length, horizontal axis longest, without free margins; anterior and posterior nares positioned mid-snout, anterior nares set further apart than posterior nares; nares with raised rims, posterior nares with elongate anterior flaps (Ref. 120898). Mouth inferior, upper and lower lips united to form oral disc; oral disc large, its width 26.3-27.2% of standard length, wider than long and covered in papillae; barbels in three pairs; maxillary barbels originating from posterolateral region of the disc just past mid-length, unbranched and short, 4.5-5.6% of standard length; lateral and medial mandibular barbels short, incorporated into lower lip and positioned on both sides of midline cleft on posterior margin of the oral disc; lateral mandibular barbel usually longer, 1.1-1.4% of standard length, than medial mandibular barbel, 0.8-1.0% of standard length; primary premaxillary teeth S-shaped with exposed brown tips, 99-116 teeth in 4 or 5 scattered rows on two ovoid tooth patches; secondary premaxillary teeth small and scattered on posterior surface of premaxillae; tertiary teeth small and needle-like, in a row near midline of dorsal edge of toothplate; mandibular teeth S-shaped, 1 or 2 rows, bunched near midline; functional rows and replacement rows usually contain 1+14 or 15+15 brown-tipped teeth (Ref. 120898). Dorsal-fin origin in anterior third of body, origin just posterior to vertical of pectoral-fin origin; dorsal fin with small spinelet, spine, and 4 or 5 rays; dorsal spine short, 9.0-9.7% of standard length, anterior margin smooth with two notches distally, posterior margin smooth; adipose fin base length long, 20.7-22.5% of standard length, and low, its height 2.6-3.9% of standard length, margin convex; caudal fin forked, rounded lobes, lower lobe longer than upper lobe, count i,7,8,i; anal-fin origin posterior to origin of adipose fin, extending just beyond adipose-fin terminus, margin convex, no sexual dimorphism observed, count iii,4-5; pelvic-fin origin posterior to the vertical of midpoint between dorsal-fin terminus and adipose-fin origin, margins convex, not reaching anal-fin origin, count i,6; pectoral fin with mostly smooth spine, two small notches on distal edge of anterior margins, relatively short, 13.3-14.3% of standard length, count I,8-9 (Ref. 120898). Lateral line complete; arising just dorsal to the horizontal level of orbit and sloping ventrally to midlateral along the side of the body towards the caudal peduncle (Ref. 120898). Postcleithral process not sexually dimorphic (Ref. 120898).
Colouration: Live colouration: body with a light brown to cream ground colour, nearly uniformly overlain with medium to dark brown melanophores (Ref. 120898). Colouration of preserved specimens: in dorsal view, cream ground colour overlain with medium to dark brown melanophores, lighter areas pre-orbit, at origin of dorsal fin, and origin and terminus of adipose fin; in lateral view, cream ground colour overlain with medium brown melanophores, mostly uniformly distributed along sides above midline and sparser ventrally; lighter small circular areas along sides just anterior to lateral line, light areas dorsal to anal-fin terminus and ventral to adipose-fin terminus; ventral surface cream, few melanophores scattered along bases of pectoral, pelvic, and anal fins (Ref. 120898). Pectoral and dorsal spines and rays cream-buff to translucent; base of dorsal fin cream with scattered melanophores; dorsal-fin rays with melanophores uniformly arranged on distal half, membranes cream to translucent; base of pectoral fin cream with scattered melanophores, rays with scattered melanophores on distal half, membranes cream; pelvic fin cream with few melanophores on rays; anal-fin base cream with scattered melanophores, rays with few scattered melanophores, membrane translucent; adipose fin cream to translucent, scattered melanophores more numerous along base; caudal fin cream to translucent, dark brown melanophores scattered at base and in distal two-thirds of upper and lower lobe (Ref. 120898).