Integrative Taxonomy Reveals Two New Dragon Millipede Species in the Genus Desmoxytes Chamberlin, 1923 from Thailand (Diplopoda: Polydesmida: Paradoxosomatidae)

Recent field surveys in northern Thailand led to the discovery of two remarkable new species of dragon millipede in the genus Desmoxytes Chamberlin, 1923. Using an integrative approach that combined morphological and molecular data, we confirmed the validity of these species, herein described as Desmoxytes chaofa Srisonchai, sp. nov. from Mae Hong Son Province and Desmoxytes sirindhornae Srisonchai, sp. nov. from Tak Province. To assess their systematic position and relationships, we conducted morphological examinations and reconstructed the phylogeny based on three gene fragments (COI, 16S rRNA, and 28S rRNA). Phylogenetic analysis supports the validity of these two new species, with genetic divergence in the COI gene clearly distinguishing them from congeners, ranging from 10.67–18.67% for D. chaofa Srisonchai, sp. nov. and 10.05–17.91% for D. sirindhornae Srisonchai, sp. nov. (mean = 14.71%). Notably, the phylogenetic tree aligns well with morphological characters, particularly those of the gonopod. Desmoxytes chaofa Srisonchai, sp. nov. is closely related to D. octoconigera Srisonchai, Enghoff & Panha, 2018, while D. sirindhornae Srisonchai, sp. nov. clusters together with D. des Srisonchai, Enghoff & Panha, 2016, both pairs exhibiting similarities in body colouration and gonopod telopodite. Based on current data, these two species are considered as narrow endemics and are restricted to limestone rock wall habitats. Complete morphological illustrations of the two new species and a distribution map of all Desmoxytes species are provided.