Taxonomic review of the Afrotropical millipede genus Scaptodesmus Cook, 1896 (Diplopoda, Polydesmida, Chelodesmidae), with integrative descriptions of three new species from Cameroon

The genus Scaptodesmus Cook, 1896, is revised based on recent material collected from Cameroon. Three new species are described and illustrated: S. kala sp. nov., S. manengouba sp. nov., and S. vandenspiegeli sp. nov. Additionally, the diagnoses of two old and well-defined species of the genus, S. porati Cook, 1896, and S. granulosus (Attems, 1931), are revised. The species Scaptodesmus dentatus Silvestri, 1909, previously regarded as incertae sedis, is here confirmed as such, since its taxonomic affiliation remains uncertain. An identification key to and a distribution map for all Scaptodesmus species known so far are provided. Barcoding base on COI sequencing was successfully performed for all three new species and compared with previously published sequences from the family Chelodesmidae. The results reveal that the three new species are all genetically distinct from one another. A maximum likelihood phylogenetic tree constructed using the dataset of available species resulted in a well-resolved and well-supported phylogeny. In all cases, barcoding data were consistent with traditional morphological taxonomic classifications. This work highlights the importance of integrated taxonomy in resolving relationships within millipede species groups below the family level.