Diagnosis: Polypterus teugelsi is distinguished from all congeners by its unique live colouration comprising a network of black marks on an olive background on the dorsal and dorsolateral surface of the body, black pectoral fins, and an orange belly (Ref. 51884). It is further distinguished from species of the Polypterus bichir group by having the dorsal spines not extending anteriorly to the vertical through the posterior margin of the pectoral fin vs. extending to that point, 28-33 predorsal scales vs. 11-16, 7-9 dorsal spines vs. 11-18, and 37-40 scales around the body vs. 42-52 (Ref. 51884). It differs from all remaining Polypterus species, except P. ornatipinnis, by having more scales in the lateral line, 63-65 vs. 51-61 (Ref. 51884). It is distinguished from P. ornatipinnis in having 7-9 dorsal spines vs. 9-11, 28-33 predorsal scales vs. 22-27, 37-40 scales around the body vs. 40-42, and a very different colour pattern (Ref. 51884). It is distinguished from the similar Polypterus retropinnis in having a longer predorsal portion of the body, the predorsal length 46,7-54,8% of standard length vs. 55,7-63,2% and distance between pectoral fin and dorsal fin 18,3-25,2% of standard length vs. 30,2-42,6%; more prepelvic scales, 48-51 vs. 44-46; fewer predorsal scales, 28-33 vs. 33-36; more pectoral-fin rays, 40-42 vs. 26-32; more vertebrae, 63-65 vs. 57-58; in the absence of the distinct black blotch on the pectoral fin base vs. presence; and in the clour pattern of the dorsal and dorsolateral portions of the body, irregular dark marks forming a network vs. large dorsal black blotches (Ref. 51884).
Description: Body elongate, subcylindrical anteriorly with posterior third laterally compressed; body depth 7,9-10,8 times in standard length; head length 5,1-6,6 times in standard length; head dorsoventrally depressed (Ref. 51884, 81628). Mouth terminal with upper jaw projecting beyond lower jaw, lips fleshy; anterior naris extending anteriorly as a nasal tentacle; eye diameter 7,1-11,3 times in head length (Ref. 51884, 81628). Gill opening large, reaching from ventral midline to upper third of body, with opercular skin flap covering base of pectoral fin (Ref. 51884). Predorsal length 46,7-54,8% of standard length (Ref. 51884). Anterior part of dorsal fin comprised of 7-9 individual spines, last spine continuous with soft dorsal fin and the latter confluent with caudal fin; 15-17 dorsal and caudal articulated rays; anal fin base short, positioned far posteriorly and proximate to caudal fin, anus immediately anterior in front of anal fin base; 40-42 pectoral fin rays; 11-13 pelvic fin rays (Ref. 51884). Scales: 63-65 lateral line scales, 37-40 scales around the body, 28-33 predorsal scales, 48-51 prepelvic scales (Ref. 51884, 81628).
Colouration: In alcohol, dorsal half of body beige to olive brown with irregular pattern of dark brown marks forming darker network pattern, distinct in juveniles, but blending into background colouration in the largest specimens; ventral half of body uniform whitish to light beige (Ref. 51884, 81628). Pectoral, pelvic, and anal fins with irregular dark brown lines on beige background; medial side of fleshy base of pectoral fin scaleless and with pattern of marbling formed by brown lines; soft dorsal, caudal, anal, and pelvic fins with vertical dark lines; lines width of fin rays; darker lines alternating with lighter lines giving checkered appearance to fins; interradial membranes along distal halves of dorsal finlets with black blotches (Ref. 51884, 81628). Horizontal dark streak extending from below eye to preopercle; second caudoventrally inclined dark streak from below eye to lower jaw; cheek, area around eye, snout, and upper and lower lips freckled with brown spots (Ref. 51884, 81628). In life, dark colour pattern of adults resembling that of preserved specimens, but colouration itself differing markedly; belly orange, ground colour of dorsal half of body olive brown with marks on body and fins black; pectorals almost entirely jetblack (Ref. 51884). Small juveniles with less conspicuous pattern of lighter brown marks on body and pectorals almost translucent (Ref. 51884).