TYPE. CANADA. Yukon. Near Otter Falls, 61°04' N, 136°59' W, aspen – white spruce community, 2800 ft, 6.VIII.1972, G.W. Scotter 20337 (CANL, holotype).
Description. Life form: lichenized fungus.
[Modified from Goward et al. 2012] Thallus appressed, moderately variable, up to 5–10 (15) cm across; lobes irregularly branched. First-tier lobes up to 3.5–4.0 (–6) mm wide, contiguous, obscuring the substrate, at the tips weakly plane to concave in cross-section, inwards becoming convex. Second-tier lobes closely appressed, usually bearing at least some soralopodia (see below), older thallus portions massing into high, symmetrical ridges and intervening depressions. Upper surface whitish to pastel green in sheltered microsites, otherwise rich chestnut brown, weakly shiny to more often dull, especially toward thallus centre, cortex firm, with occasional stress cracks, irregularly flecked with black mottling, also often with black margins as seen from above; cortidiate, gymnidiate and/or sorediate. Vegetative propagules restricted to second-tier lobes, arising in two ontological contexts: (1) apical and/or subapical soralopodia, these sparse (sometimes lacking), mostly mound-forming, up to 0.5–1.5 mm across and 0.3 mm high, at length dissolving above into granular cortidia; (2) laminal verrucae, these sparse to copious, arising both over ridges and (to a lesser extent) in intervening depressions, up to 0.5–1.0 (–1.5) mm across and 0.5 mm high, usually closely spaced from the first, remaining discrete, at length disintegrating above into coarse granular cortidia up to (40–) 50–70 (–80) mm across, these soon further dissolving into coarse proliferating soredia that often become deeply piled where sheltered (check depressions). Perforations inconspicuous, rare over lower surface of first-tier lobes, also sometimes lateral along second-tier lobes, the openings mostly tiny, , 0.2 mm across. Medullary ceiling white except darkening in vicinity of old ruptures in the lower surface. Lower surface mostly black, shiny, thin, easily torn, sharply winkled or folded. Apothecia not seen. Pycnidia sparse to numerous over upper surface; conidiospores dumbell-shaped, 4.5–5.0 3 0.8 mm.
Substrate and habitat. Corticolous on trunks and branches of conifers and nutrient-rich deciduous trees, also saxicolous over boulders in areas of low snow pack. Known only from rather dry regions.
Distribution. Rainshadow regions of inland western North America, from Alaska and the Yukon southward to southern British Columbia. Mostly at lower to middle forested elevations.