The new monotypic subgenus Stenolassus
subgen. nov. of the genus Stenohelops Reitter, 1922 is described for Stenohelops klebsi (Nabozhenko, Perkovsky et Chernei, 2016) comb. nov. (Coleoptera: Tenebrionidae), which was previously described within the genus Nalassus Mulsant, 1856. This species is transferred to Stenohelops Reitter, 1922 based on the structure of the male aedeagus, abdominal ventrite 5, and the protarsi. A key to the subgenera of the genus Stenohelops is provided. The problematic species Isomira (Mucheimira) avula
Seidlitz, 1896 is redescribed and its taxonomic placement addressed. A new species, Isomira (Isomira) hoffeinsorum
sp. nov. is also described from Baltic amber. This new species possesses a mixture of characters associated with Mucheimira and Isomira, which can be a result of incomplete diversification of the genus Isomira during the Eocene.