Pollimyrus tumifrons

3.2.5 | P. tumifrons View in CoL group

P. tumifrons (Boulenger, 1902) View in CoL (Figure S19) and its two junior synonyms, P. aequipinnis ( Pellegrin, 1924) View in CoL and P. anterodorsalis ( David & Poll, 1937) View in CoL differ from the other Pollimyrus species (except C. plagiostoma View in CoL ) by having an anal fin that is slightly shorter than the dorsal fin, whereas in the other species it is about equal or longer than the dorsal fin (90.0%–92.2% LD vs. 95.7%–223.1% LD). The dorsal fin is longer in P. tumifrons View in CoL than in other Pollimyrus species (29.3%–30.6% SL vs. 15.2%–25.4% SL) and shorter than in C. plagiostoma View in CoL (29.3%– 30.6% SL vs. 34.4%–37.9% SL). The mouth is clearly placed inferior in P. tumifrons View in CoL , whereas it is rather subinferior to terminal in other Pollimyrus species. The posterior edge of the mouth is positioned beneath the eye in P. tumifrons View in CoL , whereas it is never positioned under the eye in other Pollimyrus species. They also have, although only slightly, more pectoral-fin rays (12 vs. 9–11) than most other Pollimyrus View in CoL specimens (except one specimen of P. sp. “ kouilou-niari ” and most specimens of C. plagiostoma View in CoL ). The anterior nostril is positioned lower than the posterior one in P. tumifrons View in CoL , whereas the anterior one is positioned higher than the posterior one in all other Pollimyrus species, except P. pedunculatus View in CoL . Although this species complex shows characteristics that are different from most congenerics and is therefore easily differentiated from the other Pollimyrus species, it remains unclear to which genus P. tumifrons View in CoL would correspond better than Pollimyrus View in CoL . For this reason, the species is retained within Pollimyrus View in CoL .

Pollimyrus tumifrons View in CoL has been described from the Ubangi River near Banzyville (nowadays: Mobayi-Mbongo) in north-west DRC, P. anterodorsalis View in CoL from Panga ( David & Poll, 1937) along the Aruwimi in north-eastern DRC, and P. aequipinnis View in CoL from the Kasaï River at N'Gombe ( Pellegrin, 1924) in south-western DRC (Figure 2; also see Supplementary file S1 for hydro-geographic locations). Pollimyrus anterodorsalis View in CoL was synonymized with P. tumifrons View in CoL , by Taverne (1971a, 1971b), although, unfortunately, without further explanations. Later on, P. aequipinnis View in CoL was also synonymized with P. tumifrons View in CoL by Poll (1976), based on its overall similar appearance but, unfortunately, also without any further detailed explanation. However, morphologically, the holotype of P. aequipinnis View in CoL has a visually small snout, whereas the holotypes of the other two nominal species have large snouts. Further, P. aequipinnis View in CoL differs from both by having a shorter pre-pelvic distance (38.5% SL vs. 40.1% SL in P. tumifrons View in CoL and 43.9% SL in P. anterodorsalis View in CoL ) and more lateral-line scales (67 vs. 62 in P. tumifrons View in CoL and 63 in P. anterodorsalis View in CoL ) and more circumpeduncular scales (18 vs. 16 in P. tumifrons View in CoL and 13 in P. anterodorsalis View in CoL ). These differences would suggest that P. aequipinnis View in CoL can be a species distinct from the other two synonymized species within the P. tumifrons View in CoL group. Furthermore, two studied specimens identified as P. tumifrons View in CoL (RMCA 158002 and 158003) morphologically resemble the type specimens of both P. tumifrons View in CoL and P. anterodorsalis View in CoL in the aforementioned characteristics more than that of P. aequipinnis View in CoL , although they were collected sympatrically with the last one. Indeed, both RMCA specimens originate from the Luachimo River, which is near the type locality of P. aequipinnis View in CoL , the Kasaï River, with the former being an affluent of the latter. However, there are no data for specimens similar to the holotype of P. aequipinnis View in CoL , and no other specimens are available from the type localities of all three synonymized species to confirm the observed differences. Therefore, the alpha-taxonomic issues within this group cannot be resolved until more specimens become available. We therefore suggest to retain all three synonymized nominal species within a single valid species, P. tumifrons View in CoL , for the time being.