Two species assigned to the subtribe Hydrobiusina (Coleoptera: Hydrophilidae: Hydrophilinae: Hydrophilini) from the Late Oligocene locality of Aixen-Provence (France) are examined: Hydrobius obsoletus Heer, 1856 is removed from the Hydrophiloidea and placed in Coleoptera incertae sedis based on the examination of its holotype. Limnoxenus olenus sp. nov. is described from two well-preserved fossil specimens.
Based on a phylogenetic analysis combining the data of recent and fossil species, L. olenus sp. nov. is supported as belonging to the non-Hawaiian group of the genus Limnoxenus Motschulsky, 1853; it represents the first known fossil record of the genus.