Three new species of the millipede genus Enghoffosoma Golovatch, 1993 from Thailand (Diplopoda, Polydesmida, Paradoxosomatidae)

An examination of newly collected material from northeastern Thailand revealed three new millipede species in the genus Enghoffosoma Golovatch, 1993: E. furca sp. nov., E. parvispina sp. nov., and E. rubellum sp. nov. We utilized morphological evidence together with genetic analysis of the COI gene to validate species identification. Each of the new species has unique characteristics, particularly in the structure of the gonopodal solenophore, that easily distinguish them from other species in the genus. The interspecific p-distances calculated from 658-bp barcoding sequences between the new species and their congeners show ranges of 18.56% to 22.78% for E. furca sp. nov., 15.09% to 21.25% for E. parvispina sp. nov., and 15.09% to 22.37% for E. rubellum sp. nov., supporting the morphological distinctions. Preliminary phylogenetic trees using Bayesian inference (BI) and maximum likelihood (ML) indicate that the genus Enghoffosoma is monophyletic, with two of the newly described species forming distinct clades. Our findings increase the total number of Enghoffosoma species to 16 (including six in Thailand) and underscore a greater diversity within the genus than previously known. Morphological illustrations of the new species, derived from SEM micrographs, and a distribution map of all known species are included.