For the first time a comprehensive checklist and description of all species of the dwarf snake genus Eirenis is presented using both external morphological characters and osteological information derived from micro-computed tomography, and by considering more than 300 specimens from the entire distribution range. Our study recognizes 18 valid species, but also emphasizes that Eirenis modestus and E. persicus each represent a complex of several taxa which urgently need a revision. Regarding the latter complex, the validity of the taxon “Eirenis mcmahoni” is not accepted due to the current lack of understanding of the persicus-group. Also, further studies should be carried out to fully understand the species status of the newly described Eirenis kermanensis, which seems closely related to E. medus. At the same time, E. hakkariensis is resurrected to full species status given the dramatic morphological differences to E. thospitis, casting doubt on the apparent genetic identity as revealed by a previous investigation. In addition, our study presents the first record of E. eiselti for Syria. On the basis of our results it is for the first time possible to compile a key to all currently recognized species of Eirenis, which should be helpful for future systematic studies and faunal surveys.

Reptilia, Serpentes, Colubroidea, Colubrinae, Eirenis, Morphology, Computed Tomography.