A phylogenetic hypothesis of the subgenus Nialoe (s. lat.) of genus Pterostichus is proposed based on a cladistic analysis of seventeen morphological characters. Through comparative studies of the sclerites on the endophallus of male genitalia, it became apparent that the arrangement of these sclerites reflects seven different origins. The results show that Nialoe (s. lat.) is monophyletic and composed of four clades, while some traditional taxa are para- or polyphyletic, and are defined only by symplesiomorphies. Pterostichus (Nialoe) mosaicus sp. nov., which is indispensable for tracing the homology of sclerites in this subgenus, is described.