Thallus: crustose, thin or sometimes thick, comprised of minute verrucae, c. 0.2 mm in diam., becoming continuous or areolate, areoles up to 0.6-1 mm wide, plane or rugose, often with upturned margins surface: typically dark gray to gray-green or pale brown but sometimes lighter, shiny; margin: indeterminate; prothallus: lacking consoredia: frequently developing along cracks and the upturned margins of areoles, 0.05-0.1 mm in diam.; sometimes breaking into soredia, 25-35 µm in diam. Apothecia: innate at first and frequently erumpent, remaining adnate, frequent but not usually contiguous, up to 0.35-0.8 mm in diam. disc: black, plane, sometimes becoming fissured and/or markedly convex thalline margin: concolorous with thallus, or epinecral layer often broken at first and margin lighter gray, 0.05-0.1 mm wide, entire, persistent or becoming excluded; excipular ring: absent thalline exciple: 40-85 µm wide laterally; cortex: 5-10 µm wide; epinecral layer: c. 10 µm wide; cortical cells: up to 4-6 µm wide, pigmented or not; algal cells: up to 9-13 µm in diam. proper exciple: hyaline, 5-10 µm wide laterally, to 10-25 µm wide at periphery hymenium: 60-90 µm tall, paraphyses: 2-2.5 µm wide, conglutinate, with apices up to 3.5-4.5(-6) µm, darkly pigmented, immersed in dispersed pigment forming a dark, red-brown epihymenium; hypothecium: hyaline, (25-)50100 µm thick asci: clavate, 45-65 x 14-19 µm, 8-spored ascospores: brown, 1-septate, ellipsoid, type A development, Physcia-type, (12.5-)16-17(-20.5) x (6.5-)8-8.5(9.5) µm, lumina angular at first, becoming more rounded, but mostly retaining slightly thickened apical wall until overmature, canal very broad; torus: present at maturity; walls: not ornamented Pycnidia: c. 0.1 mm in diam., immersed in thallus, ostiole pigmented; conidiophores: type I, conidia: bacilliform, 3-5 x c. 1 µm Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: on bark of deciduous and coniferous species, and on wood, particularly of Juniperus species, at elevations of 1020-2800 m World distribution: a North American endemic with a distribution centered on the Colorado Plateau, similar to R. grandilocularis, but more widespread Sonoran distribution: Arizona, southern California, and northern Baja California. Notes: Rinodina juniperina is usually characterized by its thick thallus and shiny surface, and often by the presence of consoredia along the upturned areole margins and cracks in areole surfaces. The spores belong to the Physcia-type but the apical wall thickening becomes very slight and may ultimately disappear, resulting in a spore similar to the Physconia-type. Lignicolous specimens are usually more exposed and are therefore darker and often pale brown with better developed granules than those on more shaded, corticolous substrates. The erumpent apothecia, shiny thallus and inflated spore lumina are reminiscent of R. grandilocularis. However, that species has significantly larger, Physconia-type spores with inflated lumina from a very early stage in spore development.