Petrocephalus longianalis

General description: 

Original description from Kramer et al (2012):

Body long-oval shape. Head broadly rounded 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 22 (n = 8), 23 (n = 20), 24 (n = 18), 25 (n = 3), (e) dark spot below fin origin (lacking in samples from Luapula River bridge, SAIAB 76582). 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 30 (n = 2), 31 (n = 6), 32 (n = 16), 33 (n = 17), 34 (n = 6), 35 (n = 2). 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 = 9), 40 (n = 17), 41 (n = 21), 42 (n = 2). Scales on caudal peduncle circumference, 11 (n = 2), 12 (n = 47). Caudal peduncle slender, subcylindrical entire length, usually 19.3% (18.4–19.9%) of SL. Males with kink in anal fin base, which is absent in juveniles and females where the anal fin base is straight.

Colour in preservation: Body brown, back only slightly darker, breast and belly fair, fins rather unpigmented and transparent, anal and dorsal fin bases emphasized as dark lines. Well-circumscribed dark spot below dorsal fin origin (except for specimens from Luapula River bridge, SAIAB 76582).

Diagnostic description: 

From Kramer et al (2012):

Number of anal fin rays, nA, median 33 (range 30–35); anal fin length, LA, mean 0.261 (range 0.244–0.278) of SL; preanal length, PAL, mean 0.569 (range 0.543–0.59) of SL; depth of caudal peduncle, CPD, mean 0.298 (range 0.269–0.331) of CPL, length of caudal peduncle; body depth, BD, mean 0.267 (range 0.225–0.293) of SL; number of dorsal fin rays, nD, median 24 (range 22–26); number of scales in lateral line row, SLS, median 40 (range 39–42); distance between anterior base of pectoral fin to anterior base of pelvic fin, PPf, mean 0.152 (range 0.128–0.169) of SL.

Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith