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Molecular and morphological data uncover a new striking genus of dragon millipedes in Thailand, with alternatively long and short legs (Diplopoda, Polydesmida, Paradoxosomatidae)

Ruttapon Srisonchai , Henrik Enghoff, Natdanai Likhitrakarn, Somsak Panha, Chirasak Sutcharit

Abstract

The dragon millipedes are a unique and diverse group of diplopods, endemic to limestone habitats in South-East Asia, and yet several new genera and species are still to be discovered. Among these, a recent field survey uncovered several striking specimens featuring alternately long and short legs on each diplosegment, a morphological trait previously unseen in the family Paradoxosomatidae or any other diplopods, except for the genus Pandirodesmus Silvestri, 1932 (family Chelodesmidae). Using mitochondrial (COI, 16S rRNA) and nuclear (28S rRNA) genetic data, alongside detailed morphological analysis in order to confirm their status, we reconstructed phylogenetic trees of dragon millipedes through maximum likelihood and Bayesian inference. The phylogenetic trees strongly support the monophyly of all dragon millipedes, as well as of each nominal dragon millipede genus. The results also revealed the new specimens forming a distinctly separate clade that is closely related to Spinaxytes. Based on these findings, we establish a new monotypic genus of dragon millipedes to accommodate a new species, Alternaxytes bipectinata gen. et sp. nov., within the tribe Orthomorphini of the family Paradoxosomatidae. Morphologically, Alternaxytes gen. nov. is characterized by unique gonopodal features and heteropodous legs, suggesting a case example of convergent evolution within the Diplopoda.

IS25007  Accepted 12 May 2025

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