Thallus cushion-formed, to 3 cm broad, centrally one cm high, of mostly erect, branched, claviform squamules, apically enlarged to 2 mm, dark brown towards apices, paler brown downwards, except in dead, blackish, lower parts. Thallus to 300 μm thick; cortex sclerenchymatous, small-celled; photobiontNostoc in clusters, individual cells 5-7 μm, clusters grouped and enclosed by medullary hyphae. Apothecia brown, to 5 mm diam., usually hidden between squamules, diffuse and often complex with convex disc and excluded proper margin, surrounded by claviform side-branches. Hymenium hemiamyloid, to 150 μm; asci 8-spored with amyloid apical ring; ascospores colorless, simple, but with oil droplets, ellipsoid, 20-22 x 10-11 μm. Pycnidia not observed.
Chemistry.—All reactions negative, no lichen acids detected by TLC.
Remarks.—Fuscopannaria abscondita is a most unusual species of the F. praetermissa (Nyl.)P. M. Jorg. complex (Jorgensen 1978: 57-60), in that the squamules are more or less terete and coralloid (Fig. 3). The new species is reminiscent of the Californian F. coralloidea P. M. Jorg. in which the apothecia are clearly visible and the thallus does not form such convex cushions. In F. abscondita, the apothecia appear macroscopically as cavities among the claviform lobe-ends (Fig. 3). They are evidently formed in the early stages of the growth of the squamules and later they are overgrown and hidden (hence the epithet) by the clavuliform branchlets originating in the region around the young apothecia. The apothecia continue to expand within the resulting cushion, often appearing as deformed, complex structures, but nevertheless producing fully mature spores. This unique character may have developed as a response to the extreme Arctic environment.
Fuscopannaria praetermissa may have marginal, ascending finger-like protuberances, but these are often "frosted" and bluish, containing terpenoids and fatty acids. Such forms are mostly sterile and easily distinguished from F. abscondita.
Distribution and habitat.—As yet only known from the type collection, either usually being overlooked, or a rather local taxon. No data on the habitat conditions are included on the label, but the type specimen of F. abscondita appears among mosses (e.g., Anthelia) indicating a moist habitat, snow-bed, or wet tundra.