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The genus Polydesmus had a broad concept for a long time and would also include Acanthotarsius Verhoeff, 1931. ENGHOFF et al. (1997) already pointed out that the genus taxon Acanthotarsius shows strong relations to two members of the genus Serradium (including the type species S. hirsutipes Verhoeff, 1941), which implies the treatment of Acanthotarsius as distinct from Polydesmus. However, a synonymisation of Serradium under Acanthotarsius would have meant to exclude some Serradium species from Acanthotarsius and leave them orphaned. Therefore, ENGHOFF et al. (1997) hesitated to formalise the synonymisation and upgrading, leaving it for a comprehensive revision of the family Polydesmidae. A few years later DJURSVOLL et al. (2000) separated the genera Propolydesmus, Soleurus and Pseudomastuchus from Polydesmus but treated the subgenera Acanthotarsius, Hormobrachium and several other subgenera as subjective synonyms of Polydesmus, even suggesting that Serradium might also belong to Polydesmus sensu strictu, referring to ENGHOFF et al. (1997). Since the transfer of the former subgenus Hormobrachium from Polydesmus to Propolydesmus (ENGHOFF & GOLOVATCH 2003) it is very difficult now to assign members of other former subgenera of Polydesmus sensu lato to one of the two genera Polydesmus or Propolydesmus. Especially the members of the subgenus Acanthotarsius with their very special gonopod conformation fit neither in Polydesmus nor in Propolydesmus. The deficient treatment of the taxa Acanthotarsius and Serradium in DJURSVOLL et al. (2000) was already stated by ENGHOFF & GOLOVATCH (2003). The consequence is to upgrade Acanthotarsius now as distinct genus (stat. nov.), which includes the genus Serradium (syn. nov.) as based on its type species S. hirsutipes. Polydesmus (Acanthotarsius) edentulus as the type species of the former subgenus Acanthotarsius becomes Acanthotarsius edentulus comb. nov.