A critical revision of the churchill snoutfish, genus Petrocephalus Marcusen, 1854 (Actinopterygii: Teleostei: Mormyridae), from southern and eastern Africa, with the recognition of Petrocephalus tanensis, and the description of five new species Author Kramer, Bernd Author Bills, Roger Author Skelton, Paul Author Wink, Michael text Journal of Natural History 2012 2012-09-30 46 35 - 36 2179 2258 http://dx.doi.org/10.1080/00222933.2012.708452 journal article 10.1080/00222933.2012.708452 1464-5262 4590828 Petrocephalus magnitrunci sp. nov. ( Figure 2 , no. 31) Type specimens. Holotype : SAIAB 67069 (specimen R2 ) from Botswana , Okavango Delta , southeast of Chief’s Island , Boro River . Paratypes : SAIAB 186057 ( n = 10). Type locality. Botswana , Okavango Delta , southeast of Chief’s Island , Boro River , 19 ◦ 31 ′ 57 ′′ S, 23 ◦ 05 ′ 21 ′′ E . Diagnosis. Number of scales in lateral line row, SLS, median 40 (range 39–41); body depth, BD , mean 0.344 (range 0.327 –0.368 ) of SL ; eye diameter as defined by orbital rims, OD, mean 0.232 (range 0.218 –0.250 ) of HL , head length; number of dorsal fin rays, nD, median 21 (range 19–22); anal fin length, LA , mean 0.254 (range 0.235–0.27) of SL ; length of snout to posterior orbital rim of eye, LSo, mean 0.464 (range 0.449 –0.481 ) of HL ; head length, HL , mean 21.2 (range 17.6–24.1) times Na, distance between the pair of nares of one side . Description. Rounded-oval body of egg-like shape ( Figure 2 , no. 31). Rounded head with a small ventrally positioned subterminal mouth, situated ventral to the eye; head and body dorsolaterally compressed. Dorsal fin (a) origin situated about two-thirds of standard length from snout, (b) obliquely orientated, anteriorly higher and posteriorly lower, (c) distal margin crescentic with anterior two or three rays longer than posterior rays, and (d) number of rays 19 ( n = 2), 20 ( n = 3), 21 ( n = 5), 22 ( n = 1); no spot below dorsal fin origin. Anal fin (a) longer than dorsal fin, (b) opposite dorsal fin with slightly more anterior origin, (c) obliquely orientated, anteriorly lower and posteriorly higher, (d) anterior 10 or so rays longer than posterior ones, especially in males where they also appear stronger, (e) margin broadly rounded, (f) rays posterior to first 10 with distal margin straight, (g) number of rays 27 ( n = 1), 28 ( n = 2), 29 ( n = 3), 30 ( n = 2), 31 ( n = 3). Forked tail fin with rounded lobes. Scales cycloid with reticulate striae, scales extending anteriorly to operculum and pectoral fins (beyond pelvics). Scales in lateral series, 39 ( n = 5), 40 ( n = 3), 41 ( n = 3). Scales on caudal peduncle circumference, 11 ( n = 1), 12 ( n = 10). Caudal peduncle slender, subcylindrical entire length, usually 19.2% (17.6–21.5%) of SL ( Table 1 ). Males with kink in anal fin base, which is absent in juveniles and females where the anal fin base is straight. Colour in preservation. Intense brown, with dark back, breast and belly lighter. Ecology. The site where types were collected was a shallow floodplain lagoon on the edges of the Boro River channel and Chief’s Island . The substrate was mud and the vegetation was dense emergent grasses and water lilies ( Nymphea sp.), water depth was up to 2 m . Collection methods included daytime D-netting in the shallower margins and overnight gill-netting of the deeper sections. The lagoon was flooded during the winter flood cycle and would be dry during the low water period . Distribution. At present, only known from the Boro River in the central part of the Okavango Delta, west of the southern tip of Chief’s Island. Note that the comments of Skelton et al. (1985) on distribution, cited in the section on P. okavangensis sp. nov. , may embrace P. magnitrunci sp. nov. Etymology. Species name refers to magnus , great and truncus , trunk (such as of the body). Remarks. Petrocephalus magnitrunci sp. nov. compared with P. okavangensis sp. nov. is characterized by a greater SLS and higher BD / SL, and an apparently obligatory lack of black spot below the dorsal fin origin. Compared with both P. magnoculis sp. nov. and P. longicapitis sp. nov. , distinctly smaller OD / HL, lower nD, greater BD and greater LA in P. magnitrunci sp. nov. Compared with P. longicapitis sp. nov. : in addition to the above, greater no. of SLS, smaller HL and longer LSo in P. magnitrunci sp. nov. Compared with P. magnoculis sp. nov. : in addition to the above, shorter LSo and greater Na in P. magnitrunci sp. nov.