Thallus: crustose, thin, continuous, rimose or rarely areolate, areoles up to c. 0.5 mm wide, rugose surface: light gray to dark gray, dull; margin: thallus indeterminate; prothallus: lacking; vegetative propagules: absent Apothecia: sessile, frequent, contiguous or not, up to 0.6-0.7 mm in diam. disc: brown to black, usually pruinose, persistently plane except for some of largest and oldest apothecia thalline margin: concolorous with thallus, 0.05-0.1 mm wide, prominent in young apothecia, entire and persistent thalline exciple: 60-80 µm wide laterally; cortex: 10-15 µm; cells: up to c. 4.5 µm wide; algal cells: up to 10-13 µm in diam.; thalline exciple: 60-90 µm below; cortex: 2540 µm, columnar; excipular ring: absent proper exciple: hyaline, 10-15 µm wide laterally, expanded to 10-30 µm at periphery hymenium: 70-100 µm tall; paraphyses: 1.5-2 µm wide, not conglutinate, with apices up to 3.5-4.5 µm wide, hardly pigmented, immersed in dispersed pigment forming a light red-brown epihymenium, typically with surficial crystals, P+, developing red crystals; hypothecium: hyaline, 50-70 µm thick asci: clavate, 50-70 x 1823 µm, 8-spored ascospores: brown, 1-septate, ellipsoid, type A development, Dirinaria-type, (15-)17.5-18.5(-21) x (7.5-)9-10(-11.5) µm, lumina angular at first, becoming irregularly rounded but retaining thick apical walls, sometimes narrowly inflated at septum with K, endospore wall becoming pigmented in overmature spores; torus: hyaline, developing late; walls: lightly ornamented Pycnidia: not seen Spot tests: K+ yellow, C-, KC-, P- or P+ faint yellow Secondary metabolites: atranorin in cortex; typically with pannarin on surface of disc and adjacent proper exciple. Substrate and ecology: on twigs and small branches of deciduous and coniferous trees and shrubs at low elevations World distribution: a western North American endemic with an oceanic distribution in the coastal ranges from California to southern British Columbia Sonoran distribution: Santa Barbara Co., California, the southern limit of its range. Notes: Rinodina marysvillensis is characterized by its gray, atranorin-containing thallus, apothecia with prominent margins, and typically pruinose discs due to the presence of pannarin crystals on the surface of the epihymenium. Rinodina aurantiaca from mainly higher elevations in the Cascades and Rocky Mountains also has pannarin associated with the epihymenium but within the epihymenium rather than on its surface. This species also has a similar thallus morphology and chemistry, but has significantly larger Physcia-type spores. It also has less prominent apothecial margins and the discs may become convex.