Morphology Data of Petrocephalus arnegardi
Identification keys
Main Ref. Lavoué, S. and J.P. Sullivan, 2014
Appearance refers to
Bones in OsteoBase

Sex attributes

Specialized organs
Different appearance
Different colors

Descriptive characteristics of juvenile and adult

Striking features
Body shape lateral fusiform / normal
Cross section
Dorsal head profile
Type of eyes
Type of mouth/snout
Position of mouth sub-terminal/inferior
Type of scales cycloid scales

Diagnosis: Petrocephalus arnegardi is distinguished from all other Petrocephalus species of Central Africa by the following combination of characteristics: pigmentation pattern comprising three well-defined, bilateral black patches, one usually distinct round/ovoid subdorsal black mark situated slightly anterior to dorsal, one black mark at the base of each pectoral fin, and one ovoid black mark centered at the base of caudal fin; dorsal fin at least one third shorter than anal fin; dorsal fin with at least 20 branched rays but no more than 22; anal fin with at least 30 branched rays; 16 teeth or fewer in upper jaw, 25 teeth or fewer in lower jaw; eye relatively large, ration head length and eye-diameter less than 4.7; mouth subterminal; ration of head length to mouth position between 4.2 and 5.6; mouth small, ration head length and mouth width more than 4.1; and EOD of normal polarity, mainly biphasic with sometimes the presence of a small-amplitude positive third phase (Ref. 96601).

Description: Body ovoid, longer than high, its ration between 2.3 and 2.8, and laterally compressed (Ref. 96601). Head length between 3.4 and 4.0 times in standard length (Ref. 96601). Snout short, ration head length and snout length between 6.5 and 9.3, and round (Ref. 96601). Eye large, the ration head length and eye-diameter between 3.5 and 4.4 (Ref. 96601). Mouth small, the ration head length and mouth width between 4.1 and 5.0, subterminal, opening under the anterior half of the eye; teeth small and bicuspid, 8 to 16 in a single row in the upper jaw, 20-24 in the lower jaw (Ref. 96601). Caudal peduncle thin, the ration caudal peduncle depth and caudal peduncle height between 1.8 and 2.5 (Ref. 96601). Dosral and anal fins originate in the posterior half of the body; pre-dorsal distance slightly greater than the pre-anal distance; dorsal fin with 20-22 branched rays; anal fin with 31-34 branched rays (Ref. 96601). Scales cover the body, except for the head; lateral line visible and complete with 34 and 38 pored scales along its length; 10 to 13 scales between the anterior base of the anal fin and the lateral line; 12 scales around the caudal peduncle (Ref. 96601). Skin on head thick (Ref. 96601). The three rosettes of knollenorgans are present on the head (Ref. 96601).

Colouration: Body uniformly silvery white, with three distinct bilateral melanin marks, a distinct, ovoid black mark situated slightly anterior to the dorsal fin, sometimes covering only a few scales, a black spot at the base of the pectoral fin and a somewhat vertically orientated ovoid black mark centered at the base of the caudal fin that does not extend onto the upper and lower parts of the caudal fin; fins hyaline (Ref. 96601). Preserved colouration of body light brown, with head and dorsum slightly darker; thick skin on head opaque; numerous light melanophores on body, slightly larger ventrally from the snout to the anal fin; fins whitish/opaque (Ref. 96601).

Ease of Identification

Meristic characteristics of Petrocephalus arnegardi

Lateral Lines Interrupted: No
Scales on lateral line
Pored lateral line scales 34 - 38
Scales in lateral series
Scale rows above lateral line
Scale rows below lateral line 10 - 13
Scales around caudal peduncle 12 - 12
Gill clefts (sharks/rays only)
Gill rakers
on lower limb
on upper limb


Dorsal fin(s)

Attributes no striking attributes
Fins number 1
Finlets No. Dorsal   
Spines total
Soft-rays total
Adipose fin absent

Caudal fin

Attributes forked; more or less normal

Anal fin(s)

Fins number 1
Spines total
Soft-rays total

Paired fins

Pectoral Attributes  more or less normal
Pelvics Attributes  more or less normal
Position    abdominal  before origin of D1
Main Ref. (e.g. 9948)
Glossary ( e.g. cephalopods )
Entered by Musschoot, Tobias
Modified by Bailly, Nicolas
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