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DescriptionThallus: crustose, thick, areolate, areoles up to 0.85-0.9 mm wide, plane or rugose, or thallus poorly developed and mostly endolithic, binding substrate; surface: light gray to ochraceous, shiny or dull; margin: determinate; prothallus: lacking; vegetative propagules: absent; Apothecia: erumpent, usually remaining adnate, sometimes becoming sessile, frequent but not contiguous, up to 0.6-1.1 mm in diam.; disc: black, plane becoming convex and often fissured; thalline margin: concolorous with thallus, c. 0.05 mm wide, entire, quickly becoming excluded; excipular ring: absent; thalline exciple: 70-90 µm wide; cortex: 15-20(-30) µm wide; epinecral layer: usually present, 2030 µm wide; cortical cells up to 6-6.5 µm in diam., not pigmented; algal cells: up to 12-18 µm in diam.; proper exciple: hyaline,10-25 µm wide laterally, expanding to 40-80 µm wide at periphery; hymenium: 90-150 µm tall; paraphyses: 2-3 µm wide, not conglutinate, with apices up to 4-6.5 µm in diam., not pigmented but immersed in dispersed pigment forming a gray-blue epihymenium, N+, K+ violet, conglutinate; hypothecium: hyaline or pale yellow, 70-100(-125) µm thick; asci: clavate, 65-70 x 20-30 µm, 8-spored; ascospores: brown, 1-septate, narrowly ellipsoid, type A development, Beltraminia-type, (15.5)22.5-24.5(-31) x (7-)9.5-10.5(-13) µm, immature lumina sometimes with incipient canal, lumina mostly filling cells from first, narrow swelling at septum in some immature spores, not expanding in K, mature spores with relatively dark septum, sometimes slightly curved, finally constricted at the septum; torus: absent; walls: not ornamented (Fig. 63); Pycnidia: not seen; Spot tests: all negative; Secondary metabolites: none detected.; Substrate and ecology: found on calcareous sandstone at elevations of 1400-1830 m; World distribution: a western North American endemic with only four records known from Arizona to southern Alberta; Sonoran distribution: Arizona, locality uncertain (Ademana?) in Apache County.; Notes: Rinodina athallina has previously been compared to R. zwackhiana (Krempelh.) Körb. that also possesses a blue epihymenium (Sheard 1982), but that species has spores belonging to the Bicincta-type. Rinodina athallina may be related to R. lobulata (Sheard and Mayrhofer 2002), a primarily corticolous species, that not only has a similar epihymenium pigmentation, but also the same spore structure. The two species are well separated by the significantly smaller spores of R. lobulata and its weaker epihymenium reaction.