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DescriptionThallus: crustose, thin, areolate, areoles discrete or contiguous, up to 0.25-0.75 mm wide, rarely rimose, plane; surface: light gray, dull; margin: determinate or not; prothallus: lacking; vegetative propagules: absent; Apothecia: sessile, frequent, mostly not contiguous, up to 0.35-0.55 mm in diam.; disc: black, usually lightly pruinose (most visible when moist), plane to convex, rarely semi-globose; thalline margin: concolorous with the thallus, c. 0.05 mm wide, entire, rarely excluded; excipular ring: absent; thalline exciple: 45-70 µm wide laterally; cortex: 5-20 µm wide; cells: up to 4.5-5.5 µm wide, not pigmented; algal cells: up to 10.5-15.5 µm in diam.; thalline exciple: 60-90 µm wide below; cortex: 25-55 µm thick, columnar; proper exciple: hyaline, 5-10(-15) µm wide laterally, expanding to 10-20 µm wide at periphery; hymenium: 70-100 µm tall; paraphyses: c. 2 µm wide, not conglutinate, with apices up to 3-4 µm, lightly pigmented and immersed in a dispersed pigment, forming an orange- to light red-brown epihymenium, typically with included crystals; hypothecium: hyaline, (30-)50-90 µm thick; asci: clavate, 50-75 x 16-25 µm, 8-spored; ascospores: brown, 1-septate, ellipsoid, type A development, Physcia-type, (16.5-)19-20(-23) x (8-)9.510.5(-12) µm, lumina becoming somewhat inflated but apices mostly remaining thick walled; torus: mostly absent or narrow; walls: lightly pigmented, ornamentation light or absent; Pycnidia: not seen; Spot tests: thallus: K+ yellow, C-, KC-, P- or P+ faint yellow; epihymenium: typically P+, forming small, red needles (pannarin); Secondary metabolites: atranorin in cortex, pannarin in epihymenium.; Substrate and ecology: growing on bark of conifers and deciduous trees, frequent on dead conifer twigs, in partially shaded, moist, montane habitats; World distribution: a western North American endemic in the Cascade Range from southern British Columbia to northern California, Rocky Mountains from southern Alberta to Colorado, and southern Arizona; Sonoran distribution: Arizona, mountains of Graham and Pima counties at elevations of 2000-2745 m.; Notes: This species is very similar in habit to R. capensis but its apothecia tend to have less prominent margins and the discs become more convex. Rinodina aurantiaca typically differs in possessing pruinose discs, that are best seen when moist and are caused by the presence of pannarin crystals within the epihymenium. Both species contain atranorin, have an expanded lower cortex in the apothecia and Physcia-type spores of similar size. The species are difficult to distinguish when pannarin is absent or in low concentration in the epihymenium. They have widely overlapping distributions.