Ascomata black, subglobose, c. 120 µm diam., semi-immersed. Hymenial gel appears I+ pale red. Hamatheciumnot observed. Asci subcylindrical to obclavate, with a long internal apical beak, c. 55–60 × 11–14 µm, 6–8-spored, I−. Ascosporeshyaline to pale cinnamon-brown, narrowly elliptic (mostly) to elliptic and often slightly narrower below, (10–)15·5–20·5(–22) × (4·5–)5–6(–8·0) µm, l/b = (1·7–)2·7–3·9(–4·7) (n= 51), (1–)3-septate, not constricted at the septa, smooth-walled, without halo, guttulate, biseriate in the ascus. Growing on the bleached, possibly moribund base of the host’s podetia.
Notes. The specimen fits well the species concept of Phaeospora arctica, except staining of the hymenial gel with I, not reported before (Horáková & Alstrup 1994; Zhurbenko & Santesson 1996). The species was formerly known on Allocetraria,Arctocetraria, and Arctoparmelia, thus Thamnoliabeing a new host genus.