Diagnosis: Doumea stilicauda is distinguished from all its congeners, except D. chappuisi and D. reidi, by having the dorsolateral and ventrolateral vertebral processes extending through the dermis to form longitudinal bony ridges from slightly anterior to the base of the adipose fin posteriorly to the caudal-fin base and from somewhat anterior of the anal-fin origin to the caudal-fin base; the exposed processes are in shape of longitudinal bars with slightly corrugated surfaces that together form irregular longitudinal ridges (Ref. 85844). Doumea stilicauda differs from D. chappuisi in predorsal length 27-30% of standard length, vs. 32-37%; head length 15-17% of standard length, vs. 19-23%; caudal-peduncle length 35-41% of standard length, vs. 22-29%; and caudal-peduncle depth 19.6-25.8 times in caudal-peduncle length, vs. 7.3-14.5 times (Ref. 85844). Doumea stilicauda differs from D. reidi in predorsal length 27-30% of standard length, vs. 33%; head length 15-17% of standard length, vs. 18%; caudal-peduncle length 35-41% of standard length, vs. 22-29%); and caudal-peduncle depth 19.6-25.8 times in caudal-peduncle length, vs. 11.8 times (Ref. 85844).

Description: Body elongate and progressively tapering posteriorly; greatest body depth located slightly anterior of dorsal-fin origin other than in specimens with extended abdomen, in which greatest depth at middle of abdomen; greatest body width at anterior limit of pectoral-fin insertion other than is specimens with extended abdomen, in which greatest width at middle of abdomen; head and body of holotype covered with numerous very small papillae; papillae distributed over lateral and dorsal portions of head; ventral surface of head with small, apparently developing, close set papillae arranged in irregular rows diverging from region somewhat posterior of lower lip; papillae in this region most obvious posteriorly; small papillae also present on lateral and dorsal surfaces of anterior portion of body; middorsal ridge present between terminus of dorsal-fin base and adipose-fin origin; dorsal margins of neural arches apparent through skin, but not extending to body surface; abdominal region transversely flattened other than in specimens with distended abdomens in which abdomen somewhat transversely convex; dorsal and ventral profiles of body progressively converge from anal-fin origin to posterior end of caudal peduncle; exposed tips of dorsolateral vertebral processes apparent on skin surface from region slightly anterior of base of adipose fin posteriorly to caudal-fin base; processes on ventrolateral surface of body extend from somewhat anterior of anal-fin origin to caudal-fin base; exposed processes in shape of longitudinal bars with slightly corrugated surfaces that form irregular longitudinal ridge; lateral line complete, running along midlateral surface with short, variably spaced and grouped dorsal and ventral branches extending from main portion of system; caudal peduncle relatively elongate, slender, and dorsoventrally depressed over much of its length, but approximately one and one-half times wide as high at caudal-fin base; least depth of caudal peduncle approximately equal to two-thirds length of eye (Ref. 85844). Head broadly triangular from dorsal view with lateral margin very slightly concave to anterior margin of opercle and then slightly convex to posterior limit of opercle and snout tip rounded; head pointed and depressed from lateral view; snout long, relatively slender, and anteriorly tapering; eye situated entirely within posterior half of head; diameter of eye slightly less than one-half of interorbital distance; distance from posterior naris to anterior margin of eye distinctly less than distance between anterior naris and tip of snout; posterior naris distinctly closer to anterior naris than to eye; distance between nares of each side slightly less than distance of each to contralateral naris; mouth subterminal, small, ovoid, when open, with fleshy tuberculate upper lip and smooth firm lower lip, flanked to each side by tuberculate sections; barbels short, tuberculate, and distally tapered; maxillary barbel longest, reaching posteriorly approximately to vertical through middle of snout length; inner mandibular barbel shortest, with base located slightly lateral of midline and of lateral margin of smooth portion of lower lip; outer mandibular barbel arises from angle of mouth and extends posteriorly approximately one-half length of branchiostegal membrane; branchiostegal membrane continuous medially with central region of posterior margin slightly concave; gill slit extends posterodorsally to above pectoral-fin origin; humeral process above origin of gill opening, short; supraoccipital process narrow, peg-like, separated by gap from small trilobed nuchal shield (Ref. 85844). Dorsal fin falcate, unbranched ray longest; tip of adpressed dorsal fin extends to vertical through middle of pelvic fin; adipose-fin origin situated above middle of anal-fin base; fin small with length of base approximately one-third of distance between posterior terminus of dorsal-fin base and adipose-fin origin; fin adnate, with posterior extent of fin extending past vertical through posterior limit of anal-fin base, but not posterior of vertical through tip of adpressed anal fin; pectoral fin large and falcate with outer ray curved, pectinate, broad, and with fleshy pad covering ventral surface; innermost pectoral-fin rays short, posterodorsally orientated, and adpressed to body wall other than when fin fully extended; tip of adpressed pectoral fin falling distinctly short of pelvic-fin origin and reaching nearly to or slightly beyond vertical through posterior terminus of dorsal-fin base; pelvic fin large, slightly shorter than pectoral fin, outer ray pectinate with ventral surface with fleshy pad; pelvic-fin origin located distinctly posterior of vertical through posterior end of dorsal-fin base; tip of adpressed pelvic fin extending slightly beyond anal-fin origin; anal fin large, with distal margin straight; caudal fin forked and nearly symmetrical but with ventral lobe slightly longer than dorsal lobe; lobes small and sharply pointed with middle rays of caudal fin slightly less than one-half length of longest rays; dorsal-fin rays i,6; pectoral-fin rays i,10-11; pelvic-fin rays i,5; anal-fin rays ii-iv,6; principal caudal-fin rays i,7,6,i (Ref. 85844).

Colouration: In alcohol, body with tan to light brown ground colouration and distinctly brown dorsally and dorsolaterally; brown colouration extends somewhat ventral of lateral line across abdomen; boundary between brown and tan pigmentation distinct; brown pigmentation overlain with irregularly sized and placed darker spots of varying sizes and shapes with enclosed variably present light regions; some specimens with irregular stripe of dark pigmentation along midlateral portion of body; stripe more obvious anteriorly; dorsal and dorsolateral portions of body with four, variably obvious, distinct, dark brown saddles extending ventrally from middorsal region; anterior saddle extends from tip of supraoccipital spine to middle of dorsal fin; second saddle extends from slightly posterior of dorsal-fin base about three-quarters of distance to adipose-fin origin; third saddle begins somewhat anterior to adipose-fin origin and extends along much of base of; small fourth saddle starts slightly posterior of adipose-fin base; ventrolateral portion of abdomen with scattered dark chromatophores in some specimens, but with chromatophores absent ventrally on anterior part of abdomen; lateral line canal irregularly more lightly pigmented than surrounding regions in some specimens; distinct, narrow, dark stripe extending from somewhat posterior of terminus of pelvic-fin base posterior to above base of anal fin (Ref. 85844). Dorsal and lateral portions of head brown, with scattered slightly darker spots throughout; ventral part of head tan overall, with some fine darker pigmentation ventrolaterally but lacking chromatophores ventrally; maxillary barbel dusky, especially dorsally; mandibular barbels pale, without dark chromatophores (Ref. 85844). Dorsal surface of pectoral fin dark brown with variably developed lighter band extending from midsection of anterior rays to distal portion of posterior rays; distal margin of fin hyaline; ventral surface of fin with dusky band extending across fin approximately three-quarters of distance from base, but with distal portion of fin hyaline; dorsal surface of pelvic fin dusky other than for distal margin and basal portion of middle rays; ventral surface of fin with dusky band extending across fin approximately three-quarters of distance from base, but with distal portion of fin hyaline; dorsal-fin rays dusky overall, more so on unbranched ray and on rays and membranes distally; adipose and caudal fins dusky; fleshy pad overlying base of caudal-fin rays darkly pigmented; anal-fin rays dusky over distal one-third of anterior rays, but with margin hyaline; some specimens fixed in alcohol show bluish gray colour with spots evident on dorsal head and body (Ref. 85844).