Boulengeromyrus knoepffleri Taverne & Géry, 1968

General Description: Body laterally compressed and deep, depth 28–30% SL, greatest near the origin of the anal fin. Head long, 29–33% SL; its depth 67–77% of its length. Dorsal profile of the back straight, upper profile of headstraight, pointing downward. Ventral side of the head concave. Snout elongate, 29–35% HL, 8.2–11.4% SL. Post-orbital distance 59–64% HL. Mouth terminal, anterior to the nostrils. Sub-mental swelling reduced. Teeth slightly notched in a single row in each jaw, 3–5 above (typically 5), 4–6 below (typically 6). Nostrils close to one another, spaced 0.33–0.65 % the diameter of the eye. Nostrils well below the level of the ventral margin of the eye. Posterior nostril 1.6–2.6 times as far from the eye as the eye diameter. Eye small, 6.2–11.1% of length of the head, ringed by an unpigmented oval region of skin. Dorsal fin, 15.8–18% SL with 23–24 rays, height 14.8–16.8% SL and deeply concave. Predorsal distance 63.7–67% SL. Anal fin base length 21.8–24.5% SL with 28–31 rays, height 14.7–17.0% SL. Pectoral fin long, 17.9–21.3% SL with 12 rays. Prepectoral distance 26.4–29.5% SL. Pelvic fin length 8.1–10.5% SL; prepelvic distance 37.4–41.2% SL. Caudal peduncle length 20.1–24.8% SL, its depth 23.1–27.6% of its length. 12 circumpeduncular scales. Scales along the lateral line: 57–62. 10–12 scale rows above the lateral line, 11 below. Caudal fin deeply forked.

Preserved specimens appear dark brown above, silvery white below. A dark band runs from the tips of the longest dorsal rays to the tips of the longest anal rays. In life, specimens range from deep violet to a metalic blue color above, fading to white below the head. The longest anal and dorsal rays are dark, the more posterior anal and dorsal rays are translucent.

Size: to 413 mm SL.

EOD and electric organ: simple biphasic waveform with an average duration of 0.39 msec with an average peak FFT frequency of 3,125 Hz. The first peak, P1is about 42% of the peak to peak height. The electric organ has non-penetrating stalks innervated on the posterior side.

Link to EOD waveforms archived in the Macaulay Library

Distribution: Restricted to the Ivindo River basin of Gabon, and the Ntem river basin of Gabon & Cameroon.

Distribution map in Faunafri