The millipede family Polydesmidae from Vietnam

The millipede family Polydesmidae Leach, 1816 is almost strictly Holarctic, consisting of more than 60 nominal genera or subgenera and nearly 400 species and subspecies (Hoffman 1980; Golovatch 1991). The family is mostly distributed in the Mediterranean area, whereas Central and East Asia, as well as the entire Nearctic Region, show lower generic and, to a lesser degree, species diversity (Golovatch 1991; Djursvoll et al. 2001). Only a few macropolydesmid genera are found in Asia and Indochina including Epanerchodus Attems, 1901, Pacidesmus Golovatch, 1991, Polydesmus Latreille, 1802–1803, Nipponesmus Chamberlin & Wang, 1953, Gleninea Turk, 1945, Jaxartes Verhoeff, 1930, Schizoturanius Verhoeff, 1931, and Uniramidesmus Golovatch & Mikhaljova, 1979 (Golovatch 1991; Geoffroy and Golovatch 2004; Mikhaljova 2004; Golovatch and Geoffroy 2006, 2014; Golovatch et al. 2007; Nguyen 2009; Antić et al. 2019; Liu and Golovatch 2020). In addition, a fossil species of the rather small western to central European genus Propolydesmus Verhoeff, 1895 has recently been described from the mid-Cretaceous amber of Myanmar (burmite, 99–100 Mya) (Su et al. 2023).
Vietnam has been known to harbour a rich fauna of millipedes with about 250 recorded species (Enghoff et al. 2004 and updated). Many new species have been discovered recently, including cave millipedes, e.g. Hyleoglomeris alba Nguyen et al., 2022 (Kuroda et al. 2022), Tylopus nguyeni Golovatch, 2019, and Hylomus srisonchai Golovatch, 2019 (Golovatch 2019), but only one polydesmid has hitherto been revealed: Polydesmus vietnamicus Nguyen, 2009 from Tam Dao National Park, Vinh Phuc Province (Nguyen 2009).

The present paper updates the knowledge of the family Polydesmidae in Vietnam, with the description of a new cavernicolous species found in northwestern Vietnam. An updated key to all 12 Pacidesmus species is also presented, as well as a key to all eight genera of Polydesmidae reported so far from Asia