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Dorsal spines (total): 2-2; Dorsal soft rays (total): 7-8; Anal spines: 3-4; Anal soft rays: 7-9. Diagnosis: Synodontis denticulatus differs from its upper Lualaba and Bangweulu-Mweru congeners by the following unique combination of characters: anterior margin of pectoral spine serrated, vs. not serrated in S. pleurops; humeral process triangular and clearly pointed posteriorly, vs. not triangular and instead clearly truncated or rounded posteriorly in S. congicus, S. notatus and S. smiti; high number of mandibular teeth, 30-58 vs. lower, 0-10 in S. decorus, 18-25 in S. katangae, 23-27 in S. lufirae and 13-24 in S. polystigma; short adipose-fin length, 17.8-26.2% of standard length, vs. long, 32.3-37.1% in S. acanthomias, 30.2-36.2% in S. alberti, 32.7-42.9% in S. dorsomaculatus and 27.3-32.6% in S. nigromaculatus; and a non-villous skin on flanks vs. villous skin in S. greshoffi and S. unicolor, short maxillary barbels, 77.6-123.3% of head length vs. usually longer, 108-195% in S. greshoffi and 83.6-165.3% in S. unicolor, a low number of short serrations on anterior margin of pectoral spine, 8-14, vs. high number of long serrations, 9-23 in S. greshoffi and 11-20 in S. unicolor, and a high number of serrations on posterior margin of dorsal spine, 7-15, vs. a low number of serrations on posterior margin of dorsal spine, 2-15 in S. greshoffi and 5-11 in S. unicolor (Ref. 122878). Furthermore, Synodontis denticulatus differs from the remaining of its Congo Basin congeners, including those from Lake Tanganyika basin and associated river systems, by the following unique combination of characters: dorsal spine without strong serration on its anterior margin vs. with strong serrations in S. batesii and S. longispinis; dorsal spine with strong serration on its posterior margin vs. no serrations in S. nigriventris; humeral process triangular and clearly pointed posteriorly vs. triangular but instead with a clearly blunted point posteriorly in S. dhonti, not triangular and instead clearly truncated posteriorly in S. robertsi; high number of mandibular teeth, 30-58, vs. low, 14-18 in S. brichardi, 20 in S. camelopardalis, 20-27 in S. flavitaeniatus, 15-29 in S. irsacae, 19-30 in S. longirostris, 14-24 in S. multipunctatus, 12-19 in S. nummifer, 18-23 in S. pardalis, 17-28 in S. schoutedeni, 17-26 in S. grandiops, 13-19 in S. ornatissimus and 10 in S. vaillanti; short adipose-fin length, 17.8-26.2% of standard length, vs. long, 30.7-34.8% in S. caudalis, 28.2-31.4% in S. cuangoanus, 35.4-37.1% in S. depauwi, 29.4-33.7% in S. iturii, 31.6% in S. multimaculatus, 33.2-40.0% in S. petricola, 29.2-45.6% in S. polli, 29.7-34.1% in S. soloni, 28.2-33.3% in S. victoriae, 31.2-44.8% in S. ilebrevis, 27.6-38.7% in S. lucipinnis and 28.0-33.4% in S. macropunctatus; non-villous skin on the flanks vs. villous skin in S. afrofischeri; its unique body colouration characterised by dark brown or black, dark-grey, spots and marbling on a yellowish, light brown, background vs. body with brownish to black background with small, light brown spots and sometimes with vertical sinusoid bars as well in S. angelicus, body dark brown to blackish covered with lighter vermiculations in S. aterrimus, body with distinct, large, dark brown, black spots on a lighter coloured network in S. centralis, uniformly brownish body, or with small, black spots on upper and lower part of flanks in juveniles in S. granulosus, body greyish to cuprous brown in colour with numerous small black spots, sometimes confluent in S. melanostictus, uniform brownish body colouration with or without numerous, small, black spots in S. nigrita, body with six vertical dark brown bars in juveniles modified more or less into two series of, unequally sized, dark brown spots in S. ornatipinnis, body with a few, large, rounded, back spots only in S. pulcher, yellowish or beige to whitish coloured body covered with large, dark brown spots in juveniles, becoming uniformly greyish with size in S. rukwaensis, and body with a uniform greyish background colour with or without numerous small black spots in S. tanganyicae and S. zambezensis; and long maxillary barbels, 77.6-123.3% of head length, vs. shorter, 50.5-75.8% in S. contractus (Ref. 122878). Finally, Synodontis denticulatus differs from its congeners from southern Africa by the following unique combination of characters: a high number of mandibular teeth, 30-58, vs. low, 12-22 in S. leopardinus, 18-27 in S. macrostigma, 13-21 in S. macrostoma, 12-24 in S. nebulosus, 17-28 in S. thamalakanensis, and 14-24 in S. woosnami; a short adipose-fin length, 17.8-26.2% of standard length, vs. long, 27.3-32.6% in S. nigromaculatus; and its unique body colouration characterised by dark brown spots and marbling on a yellowish, light brown, background vs. dark brown to black, eye-sized, markings, usually spot or bars merging into a maze-like network, on a light brown to olive brown background in S. vanderwaali, and a uniform greyish background colour with or without numerous small black spots in S. zambezensis (Ref. 122878).
Description: A small species with a high decurved head profile, postdorsal profile straight, inclined posteriorly (Ref. 122878). Three pairs of barbels; maxillary barbel long, sometimes surpassing head length, 77.6-123.2% of head length, unbranched and without or with a basal membrane, the latter, when present, not extending the width of the barbel thread itself; outer mandibular barbels measuring 46.0-70.8% of head length, with numerous short and paired tuberculate branches; inner mandibular barbels measuring 22.7-48.1% of head length, with numerous short, often paired, tubercle branches, many secondary branches present (Ref. 122878). Large eyes, measuring up to one third the length of the head; two pairs of well-spaced nostrils situated near the tip of the snout, anterior nostrils slightly closer towards each other than posterior ones; anterior nostrils with a short raised rim, posterior nostrils with an elevated flap along anterior margin (Ref. 122878). Unicuspid teeth, their distal end sharply curved upwards, primary premaxillary teeth arranged in several irregular rows, numerous mandibular teeth, 31-48, organised in a single row with replacement teeth in an irregular second row situated in front of the former (Ref. 122878). Dorsal fin a spinelet, a spine and 7-8 rays; dorsal spine almost straight, almost smooth along its anterior margin, but sometimes with 1-3 slight serrations on its distal part, posterior margin with 7-14 strong serrations on 3/4 of its distal part; adipose fin small; pectoral fin with 1 spine and 7-8 rays; pectoral spine, slightly curved posteriorly, with 8-14 strong serrations on its anterior margin and numerous fine serrations, 18-31, on its posterior margin; distal tip of pelvic fin does not reach origin of anal fin; ananl fin with 3-4 spines and 7-9 rays; caudal fin forked, with upper lobe slightly longer than lower lobe and both slightly pointed (Ref. 122878). Lateral line complete, curved slightly upward at humeral process and nuchal plate, straight further posteriorly and inclined towards base of caudal fin (Ref. 122787).
Colouration: In life, the body and head are covered with irregular, dark brown spots, giving the appearance of marbling on a light brown, yellowish, background; ventral side of body also with an overall light brown-yellowish background colour; barbels brownish with, when present, basal membrane on maxillary barbels black; all fins yellowish-white in overall background colour, with brownish fin rays and finely punctuated with regular dark brown spots; caudal fin with two elongated dark brown blotches, one on the upper and one on the lower fin lobe, both especially marked on the longest fin rays; sometimes adipose fin darker than other fins and then punctuated with regular dark brown spots only on its periphery; eyes with a light brown iris while pupil is brilliant black (Ref. 122878). Two overall colour variants seem to occur, those with a yellowish-brown overall appearance and which seem to be most abundant in the rivers and those with a yellowish-black to yellowish dark-grey overall appearance and which seem to abound in both Lake Bwaya and Lake Pungwe (Ref. 122878). On specimens preserved in alcohol, the light brown, black, or dark grey overall background colour remains but, the yellowish background also becomes light brown or pale instead, while the brown spots become darker; on the fins, the yellowish colour also disappears and becomes light brownish or beige while the dark brown punctuations become less marked (Ref. 122878). |
