Two new millipede species of the genus Pimvichai, Enghoff, Panha & Backeljau, 2020 (Diplopoda, Spirobolida, Pseudospirobolellidae).

Two new millipede species of the genus Pimvichai, Enghoff, Panha & Backeljau, 2020 from Thailand are described: from Loei Province and from Uttaradit Province. The descriptions are based on gonopod morphology and two mitochondrial gene fragments (COI and 16S rRNA). The phylogenetic mtDNA analysis assigned the two new species unequivocally to the consistently well-supported clade, in which they form a fifth subclade that was well supported by maximum likelihood analysis of 16S rRNA, though neither by Bayesian inference nor by COI. The two new species share four conspicuous gonopodal synapomorphies of the genus: (1) the protruding process on the coxae of the 3 (and sometimes 4) pair of male legs, (2) a large, triangular coxae on the 4-5 pair of legs, (3) a short process of the preanal ring protruding as far as, or slightly beyond, the anal valves, and (4) the posterior gonopod telopodite divided into two parts, with a conspicuous pore opening at the mesal margin at the end of the coxal part of the posterior gonopod. Thus, the two new species provide further evidence of the well-defined monophyly of the genus . Finally, the paper provides an updated morphological identification key to all currently described species.