Systematic position of marine littoral Pseudothinusa Tasaku and Maruyama (Coleoptera: Staphylinidae: Aleocharinae) based on morphological and molecular evidence

A systematic study of the coastal Athetini monotypic genus Pseudothinusa Tasaku and Maruyama is presented using morphological and molecular characters. Detailed examination of the voucher specimens of P. sunahama Tasaku and Maruyama revealed that they represent a species of Adota Casey based on the following combination of characters: body surface with isodiametric microsculpture; antennomere 2 longer than 3; medial lamellae of internal sac of median lobe of aedeagus reduced; spermathecal duct coiled once distally. The proposed synonymy of Pseudothinusa under Adota was also supported by gene tree criterion (PA, BA, and ML trees) using partial COI and 28S gene sequences. This new synonymy (Adota Casey, 1910 = Pseudothinusa Tasaku and Maruyama, 2023, new syn.) necessitates the following new combination: Adota sunahama (Tasaku and Maruyama), new comb. We also provide scanning electron microscopy (SEM) micrographs for their diagnostic characters. A checklist of Adota from the world and a key to species of Adota are presented.