In our study of the pachylaelapid mites from Iran, a new remarkable species, Pachylaelaps (Pachylaelaps) prodigiosus sp. nov., is described and illustrated based on adult stages found in soil detritus of broadleaved deciduous forest habitats. The sperm induction system detected in females of the new species is unusual in having its tubular structures exclusively associated with coxae III instead of coxae IV, as found in all other members of the genus. An adult male of P. (P.) grandis Koroleva, 1977, a similar species with analogous sperm induction system in female, is described for the first time. A new species group in the subgenus Pachylaelaps, represented by P. (P.) grandis, P. (P.) kirghizorum Koroleva, 1977 and P. (P.) prodigiosus sp. nov., is newly constituted, and its specific characters of insemination apparatus discussed.