A new species of the millipede genus Attems, 1907, from northern Thailand (Polydesmida, Pyrgodesmidae).

The millipede family Pyrgodesmidae and the genus are recorded from Thailand for the first time, being represented there by The new species is distinguished by the evident apicodorsal trichostele on the last tibia of both sexes and the gonopodal telopodite being particularly complex, quadripartite, consisting of the longest, mesal, suberect solenomere branch; a slightly shorter, similarly slender, acuminate endomere branch tightly appressed to the solenomere; a somewhat shorter, caudal, strongly curved, armed exomere process; and a very distinct, low, lateral, sac-shaped velum at their base. This situation strongly resembles the one observed in the geographically closest Golovatch & VandenSpiegel, 2015, from Myanmar, but the shapes and armament of all outgrowths of the gonopodal telopodite are clearly different. A key to all three pecies known from Indochina or Myanmar and an updated checklist of all 21 species of the genus are provided.