New Polypterus described

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A new species of Polypterus, originally discovered by fishkeepers in the aquarium trade, has just been described by scientists.

The species, which has been available in the shops under the temporary trade name Polypterus sp. "Congo", is similar to Polypterus retropinnis.

It has just been named Polypterus mokelembembe by Frank Schafer and Ulrich Schliewen in the systematics journal Zootaxa.

During the study, Schliewen and Schafer studied retropinnis and Polypterus in museum collections and found that some of these already contained the "new" species.

Indeed, the original description of Polypterus retropinnis, which was written in 1899, was actually based on both retropinnis and mokelembembe, so Schafer and Schliewen have also redescribed retropinnis to clarify its features.

Effectively, the new species mokelembembe is described from the holotype of P. retropinnis, and retropinnis has been redescribed using Polypterus sp. "Congo" as the new type material.

Spot the differenceWhile fishkeepers have been able to differentiate the new species from retropinnis and its relatives on the basis of colour, the study has shown that the fish also has a distinctive number of predorsal scales.

P. retropinnis, palmas palmas, and the relatively recently described P. teugelsi, also have 32-37 predorsal scales, rather than the 11-28 seen in other species, but colour and some other characters can be used to distinguish the species.

Schliewen and Schafer say: "It differs from P. teugelsi by having 57-60 lateral line scales (vs. 63-65), from Polypterus palmas palmas by a single large black blotch on pectoral fin base (vs. numerous small spots on posterior part of base), and from P. retropinnis in having a wider first dorsal spine (6.4-8.1 vs 4.6-6.1% of HL), a shorter internostril distance (11.6-13.7 vs 14.3-18% of HL), and fewer pectoral fin rays (23-29 vs 30-34)."

P. mokelembembe also has a set of irregular blotches that form saddles, and there's no distinct border between the darker colour of the back and the paler colour of the belly, as you tend to see in retropinnis, teugelsi, palmas and weeksii.

The fish is known from several places through the Congo basin, including the Tshuapa drainage in the Democratic Republic of Congo and the Alima drainage in the Republic of Congo.

Those fishes in the aquarium trade are reportedly collected from a blackwater stream at Kinkole, east of Kinshasa.

The fish is named after the Mokele-mbembe, a mythical creature believed to be a dinosaur that survived after the extinction of other dinosaurs. Polypterids are ancient fishes, and are the sister group to fishes that were around at the time dinosaurs roamed the earth.

For more details on the new polypterid see the paper: Schliewen, UK and F Schafer (2006) - Polypterus mokelembembe, a new species of bichir from the central Congo River basin (Actinopterygii: Cladistia: Polypteridae). Zootaxa, 1129: 23-36.