Diagnosis: A small, laterally spotted haplochromine which is recognized by the following combination of characters: prominent, quadrate suprapectoral spot spanning subdorsal vertical bars 3-4, this spot below and touching the upper lateral line and usually extending slightly above it; 13-15 lower-limb gill rakers; and deep body, depth 34.4-38.2% of standard length (Ref. 119408). The shape and placement of the suprapectoral spot distinguish Otopharynx panniculus from O. brooksi, O. lithobates, and O. ovatus, in all of which this spot lies entirely below and usually separated from the upper lateral line; its shorter lateral line of 31-33 scales discriminates O. panniculus from O. decorus with 36-38 scales, O. argyrosoma with 34-36 scales, and O. selenurus with 34-35 scales; its higher gill raker count of 13-15 on lower limb distinguishes O. panniculus from O. tetrastigma with 9-11, O. speciosus with 11-12, and O. antron with 10-11; its shorter head, 31.9-33.7% of standard length, and longer caudal peduncle, 18.8-21.7% of standard length, distinguish O. panniculus from O. spelaeotes, with head 34.8-36.6% of standard length and caudal peduncle length 13.2-15.6% of standard length; its 15-16 dorsal-fin spines and lack of dorsal midline spots separate O. panniculus from O. heterodon, which has 17-18 dorsal spines and five or six distinct, small, dark dorsal midline spots just below the dorsal-fin base; the presence of several slightly enlarged teeth in the median columns of the lower pharyngeal bone separates O. panniculus from O. auromarginatus and O. tetraspilus, which have only small, compressed, bicuspid pharyngeal teeth; in O. panniculus the lips are thin and lack median lobes, distinguishing it from O. pachycheilus with lips hypertrophied, with prominent median lobes (Ref. 119408). Compared to O. aletes, O. panniculus has fewer lateral-line scales, 31-33 vs. 34-36; and a lighter lower pharyngeal jaw and dentition, with small, laterally compressed, bicuspid posteromedian pharyngeal teeth vs. these teeth enlarged, molarized; slender posterior horns vs. horns thickened; and anterior blade longer, shallower vs. blade shorter, deeper (Ref. 119408). Compared to O. peridodeka, O. panniculus has fewer lateral-line scales, 31-33 vs. 34-35; usually has more lower-limb gill rakers, 13-15 vs. 11-13; and lower pharyngeal teeth more uniform in size, those of the median columns scarcely larger than the more lateral teeth vs. posterior teeth of median columns distinctly enlarged relative to lateral teeth (Ref. 119408). Otopharynx panniculus superficially resembles Trematocranus "brevirostris deep", but that still-undescribed species is from substantially deeper water, 90-102 m vs. about 42 m; the suprapectoral spot apparently spans subdorsal bars 2-3 vs. bars 3-4 in O. panniculus; and there are 10-13 lower-limb gill rakers vs. 13-15 (Ref. 119408). Trematocranus brevirostris itself is also similar, but in O. panniculus the suprapectoral spot is roughly square, covers four to five longitudinal scales, and is located almost entirely below the upper lateral line vs. taller than long, covers three scales,and at least in the lectotype is placed more above than below the upper lateral line; the cephalic lateral-line system is not enlarged vs. pores and canals of the preorbital, nasal, dentary, and lacrimal bones inflated; there are 52-66 outer upper-jaw teeth vs. about 43; and 3-4 cheek scale rows vs. 2 (Ref. 119408).

Description: Deep-bodied, body depth 34.4-38.2% of standard length (Ref. 119408). Dorsal profile straight above snout, then evenly convex to end of dorsal-fin base; premaxillary pedicels not prominent, their angle 42-50°, interorbital angle 36-46°, nuchal angle 20-28°; ventral profile a less-convex mirror image of dorsal profile (Ref. 119408). Jaws equal anteriorly or lower projecting very slightly, lower jaw dorsoventrally somewhat flattened; lips thin and not lobate; gape inclination 30-42°; lower-jaw length-width ratio narrow, the hemijaws, as seen from below, converging toward the rear and nearly touching posteriorly; lower-jaw underside angle 27-40°; snout acuteness 77-80°; eyes large, 36.5-38.8% of head length, round; pupil pointed anteriorly, rounded posteriorly; eye nearly reaching dorsal head profile (Ref. 119408). Caudal peduncle 18.8-21.7% of standard length, its length 1.7-2.0 times its depth (Ref. 119408). Soft dorsal and anal fins produced, more so in males; caudal fin emarginate; pectoral fin 38.0-42.3% of standard length, reaching beyond level of third anal-fin spine base; pelvic fin 23.1-31.7% of standard length (Ref. 119408). Dental arcade of each jaw rounded; upper jaw with 52-66 teeth in outer row; movably implanted, rather closely spaced; anterior and anterolateral teeth unequally bicuspid with acute cusps, crowns slightly incurved; occasional unequally tricuspid teeth present; posterior teeth unicuspid with acute crowns; lower-jaw outer tooth row of haplochromis type, with 40-62 teeth; crowns similar to those of upper jaw; lower jaw somewhat flattened, dorsoventrally shallow, so that anterior and anterolateral teeth are implanted with shafts angled outward; inner teeth small, unicuspid to weakly tricuspid, in two rows spaced closely one behind the other (Ref. 119408). Lower pharyngeal bone subtriangular, appearing lightly built in posterior view; posterior contour emarginate, each half slightly convex, the halves meeting at an obtuse angle, horns slender, rather long; median suture straight; keel long, shallow, straight, its length about twice its depth; weakly convex below; dentigerous surface somewhat concave in lateral view; one to four posterior teeth of each median column slightly enlarged but cuspidate, not molarized; lateral teeth small, bicuspid, rather crowded; teeth in posterior row 39-48, in each median column 9-13, in each oblique row 6-10 (Ref. 119408). Lacrimal bone bearing four neuromasts and five lateral-line pores; lacrimal notch obsolete (Ref. 119408). Gill rakers 13-15 on lower arch; slender, unbranched; melanophores variably present on outer surface of outer-arch rakers (Ref. 119408). Scales ctenoid; 31-33 in lateral line; lateral line discontinuous, upper section with downward kink three to four scales long, or lacking a kink; squamation extending onto caudal fin between fin rays, to near tips of upper and lower lobes and on basal one-third of fin along middle rays; soft dorsal and anal fins with a few small scales between bases of some rays; larger scales of lower flank transition gradually to smaller chest and belly scales between bases of pectoral and pelvic fins (Ref. 119408). Vertebrae 32 (Ref. 119408).

Colouration: Live colouration of males and females is unknown; however, a freshly trawled male of Otopharynx "brevirostris yellow", thought to be O. panniculus, is silvery on flanks, white on chest, with about six gray vertical bars below dorsal-fin base, lower half of head bright orange-yellow, suprapectoral spot and faint supraanal and precaudal spots steel-blue, dorsal fin lappets orange distally, whitish proximally, orange maculae between soft rays, caudal fin brownish with orange maculae, anal fin pale with three or four large yellow eggspots, pelvic fin apparently with black leading edge, pectorals hyaline; the trawled female is predominantly silvery to white on body, chest, and head; three distinct lateral spots, vertical bars faint; oval orange markings evident throughout dorsal and caudal fins (Ref. 119408). Colouration in preservative: upper and lateral head surfaces light brown, nuchal area darker; upper half of lacrimal dark brown; operculum silvery with faint brown posterodorsal spot; underside of head, including branchiostegal membrane and geniohyoid area between left and right hemijaws, dark brown in males; flanks light brown above midline, silvery below; no distinct dorsal midline spots; chest peppered with dark pigment in males; eight or nine dark vertical bars below dorsal-fin base, narrower than or equal to the interspaces; two to three fainter bars on caudal peduncle; suprapectoral spot square to parallelogram-shaped, darker brown than bars, extending longitudinally between subdorsal bars 3 and 4, covering four to nearly five lateral-line scales, and vertically from just above lateral midline of flank to one-half scale above upper lateral line; supraanal spot small, variably present, appearing as a darkening on last subdorsal bar between lateral lines; precaudal spot on lower lateral line at end of caudal peduncle, slightly more distinct than supraanal spot; dorsal fin brownish with pale lappets; no submarginal stripe; indistinct marbling in soft dorsal; anal fin brownish, shading in males to black on distal half; no eggspots visible; caudal brownish without distinct markings; pelvics of males blackish with narrow pale leading edge; pectorals pale yellow, transparent (Ref. 119408).