| abstract | A new species of the family Brachychthoniidae (Acari: Oribatida), Arcochthonius roynortoni n. sp., found on the summit of the Festkogel mountain (3030 m a.s.l.) in the Central Alps (Obergurgl, Tyrol, Austria), is described and illustrated, based on adults. Arcochthonius n. gen. is proposed for this species. The relationships to the closely related genus Synchthonius Hammen, 1952 and other genera of Brachychthoniidae are discussed. The new species is unique among Brachychthoniidae in having arched ridge-like sculpturing on thickened anterior edges of medial and posterior notogastral sclerites, and differs by a combination of morphological character states. Some notes on ecology and biology are given. |