New insights into Plutonium, one of the largest and least known European centipedes (Chilopoda): distribution, evolution and morphology

Plutonium zwierleini is one of the largest scolopendromorph centipedes in Europe and is known for debates on the evolution of segmental body pattern in arthropods. However, only 24 records have so far been reported and probably only a dozen specimens still exist in collections. Based on 19 new data from professionals and amateur recorders, we confirmed that populations are present today in four disjunct areas: southern Iberian Peninsula, Sardinia, southern Italian Peninsula and Sicily. A phylogenetic analysis of the first molecular data obtained for Plutonium (16S, COI, 18S, 28S) provided strong evidence that it is closely related to Theatops, either sister to the latter or nested within it, with an estimated separation since the Mesozoic. By examining specimens of Plutonium from all the four inhabited areas and specimens of most of the species of Theatops, we also documented many synapomorphies uniting Plutonium and Theatops (brown-orange colour, whitish patches replacing the ocelli, a particular denticulation on the forcipules, conspicuously swollen and piercing ultimate legs) and some derived characters unique to Plutonium, including the blade-edged claws of the ultimate legs and the previously overlooked presence of long, dense setae on most other legs, in both sexes and in the entire species range.