Pollimyrus isidori

Dierickx, Katrien, Lunkayilakio, Soleil Wamuini, Bills, Roger & Vreven, Emmanuel, 2025, Morphometric synthesis of Pollimyrus (Teleostei, Mormyridae) with the description of four new species, Journal of Fish Biology 106 (3), pp. 846-892 : 859

3.2.2 | P. isidori group

This group consists of three currently valid species: P. isidori (type species of Pollimyrus ), P. fasciaticeps , and P. nigricans .

Pollimyrus isidori (Valenciennes, 1847) (Figure S10) differs from both the other species of the group by its higher number of dorsal-fin rays (20 vs. 14–17 in P. nigricans and 17 in P. fasciaticeps ) and more pelvic–anal scales (16 vs. 12 and 14, respectively). It can further be distinguished from both the other species by its deeper body (33.3% SL vs. 23.5%–29.5% SL in P. nigricans and 29.7% SL in P. fasciaticeps ). Finally, it has very short pectoral fins that do not reach halfway of the pelvic fin (vs. almost reaching the distal tip of the pelvic fin in P. nigricans and P. fasciaticeps ).

Pollimyrus nigricans (Boulenger, 1906) (Figure S11) differs from the other two species, P. isidori and P. fasciaticeps , by having a shorter dorsal fin (16.0%–19.1% SL vs. 22.5% SL and 22.3% SL), a shorter post-dorsal distance (35.5%–37.5% SL vs. 42.8% SL and 43.5% SL), a larger postorbital distance (62.4%–67.3% SL vs. 57.3% SL and 52.2% HL), a slightly shorter anal fin (21.0%–24.6% SL vs. 26.8% SL and 27.7% SL), and fewer pelvic–anal scales (12 vs. 16 and 14). This species also has longer but not pointed anterior parts of the dorsal and anal fins (vs. pointed in P. fasciaticeps ). The pectoral fins almost reach the posterior tip of the pelvic fins (vs. not reaching halfway the pelvic fin in P. isidori ).

Pollimyrus fasciaticeps (Boulenger, 1920) (Figure S12) was originally described based on a single specimen. The holotype can be distinguished from the type specimens of the other two species by the longer distance between the snout and the anterior eye margin (50% HL vs. 41.4% HL in P. isidori and 37.5%–42.6% HL in P. nigricans ), slightly shorter pre-dorsal distance (61.6% SL vs. 63.8% SL in P. isidori and 64.5%–67.8% SL in P. nigricans ), and having a higher number of dorsal–lateral scales (16 vs. 14 in P. isidori and 11–14 in P. nigricans ). It can further be distinguished from P. isidori by the wider head (59.7% HL vs. 50.9% HL). This species also has pointed anterior parts of the dorsal and anal fins (vs. longer but not pointed in P. isidori and P. nigricans ). The pectoral fins almost reach the posterior part of the pelvic fins (vs. not reaching halfway the pelvic fin in P. isidori ).