Basionym. Buellia luridata Körb., Parerg. lich. 188 (1860). Type. GERMANY. Bayern. an Kalfelsen bei Bissingen in Oberamt Ulm, s.d. C.A. Kemmler s.n. ( L - holotype).
Rinodina euryspora A. Zahlbr. ex Hasse, Bryologist 18: 23 (1915) Type. U.S.A. CALIFORNIA. [Los Angeles Co.,] Highland Park, near Pasadena, s.d. H.E. Hasse 1129 (W - holotype, FH - isotype!).
Description.Thallus crustose, thin or thick, areolate; areoles contiguous, to 0.5-1.0 mm wide, margins sometimes raised, to subsquamulose, plane or somewhat rugose; surface whitish, ochraceous to brownish, matt or shining; margin determinate; prothallus absent; vegetative propagules absent; Apothecia erumpent, innate to broadly attached, usually one per areole, frequent, to (0.3-)0.6-0.7 mm in diam.; disc concave to plane or slightly convex, black, mostly pruinose; thalline margin concolourous with thallus, 0.05-0.10 mm wide, entire, persistent or becoming partly excluded; excipular ring sometimes present, raised. Apothecial Anatomy. Thalline exciple (40-)60-120 µm wide; cortex 5-20 µm wide; epinecral layer 10-30 µm wide; crystals absent in cortex and medulla; cortical cells to 4.5-7.5 µm wide, pigmented or not; algal cells to 10.0-20.0 µm long; proper exciple 10-15 µm wide laterally, expanding to 15-50 µm at periphery; hypothecium hyaline to yellowish, 70-100 µm deep, extending into a stipe below; hymenium 70-90 µm high, not inspersed; paraphyses 2.0-3.5 µm wide, not conglutinate, with apices expanded to 4.0-6.5 µm wide, darkly pigmented, often including the penultimate septa, immersed in dispersed pigment forming a red‑brown epihymenium; asci 50-65 x 17-23 µm. Ascospores 8/ascus, Type A development, Bicincta-type, (10.5-)13.0-14.0(-17.0) x (7.5-)8.5-9.0(-10.5) µm, average l/b ratio 1.4-1.6, outer wall thickened at septum and apices when young, lumina quickly becoming rounded, spores becoming constricted when overmature, pigmented band around each cell; torus absent, walls not ornamented. Pycnidia not seen.
Chemistry. Spot tests all negative; secondary metabolites, zeorin present.
Substrate and Ecology. Saxicolous, on caliche and calcareous rocks, 320-2,015 m elevation.
Distribution. The species is infrequent in the western United States, from Washington and North Dakota in the north to southern California. Also known to be scattered in Scandinavia, the mountains of southern and central Europe, north Africa, and in Australia and New Zealand (Kaschik 2006).
Notes. This species is characterized by its small, Bicincta‑type spores, its usually ochraceous and areolate thallus with innate to broadly attached apothecia and pruinose discs. Rinodina luridata has been compared to R. lecanorina by Mayrhofer et al. (1990), a species with a thicker thallus, larger apothecia and larger spores, and which is not known from North America.
Specimens examined. U.S.A. CALIFORNIA. Los Angeles Co., Pasadena, 1906, H.E. Hasse (FH); San Clemente Island, W.A. Weber 42652 (COLO); Santa Monica, H.E. Hasse (MICH). COLORADO. Rio Blanco Co., Piceance Creek, 1959, W.A. Weber (COLO). NEVADA. Elko Co., 6 mi W state line, US 40, C.M. Wetmore 16645 (MIN). NEW MEXICO. San Juan Co., J. Marsh 359; Chaco Canyon Nat. Mon., T.H. Nash 16361 (both ASU). NORTH DAKOTA. Billings Co., T. Roosevelt Nat. Park, R.L. Dix 81 (WIS). SOUTH DAKOTA. Lawrence Co., 5 mi NW Spearfish, C.M. Wetmore 11222a (MSC). WASHINGTON. Benton Co., Horse Heaven Hills, B. McCune 23932 (personal herb.).
Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.
Thallus: crustose, thin or thick, areolate, areoles contiguous, up to 0.5-1 mm wide, margins sometimes raised, plane or somewhat rugose surface: white, ochraceous to brownish, dull or shiny; margin: determinate; prothallus: absent; vegetative propagules: absent Apothecia: erumpent, becoming adnate, usually one per areole, frequent, up to (0.3-)0.6-0.7 mm in diam. disc: concave to plane or slightly convex, black, mostly pruinose thalline margin: concolorous with thallus, 0.05-0.1 mm wide, entire, persistent or becoming partly excluded; excipular ring: sometimes present, raised thalline exciple: (40-)60-120 µm wide; cortex: 5-20 µm wide; epinecral layer: 10-30 µm wide; cortical cells: up to 4.5-7.5 µm wide, pigmented or not; algal cells: up to 10-20 µm in diam. proper exciple: 10-15 µm wide laterally, expanding to 15-50 µm at periphery hymenium: 70-90 µm tall, paraphyses: 2-3.5 µm wide, not conglutinate, with apices expanded up to 4-6.5 µm wide, darkly pigmented, often including the penultimate septa, immersed in dispersed pigment forming a red-brown epihymenium; hypothecium: hyaline to pale yellow, 70-100 µm thick, extending into a stipe below asci: clavate, 50-65 x 17-23 µm, 8-spored ascospores: brown, 1-septate, broadly ellipsoid, type A development, Bicincta-type, (10.5-)13-14(-17) x (7.5-)8.5-9(-10.5) µm, outer wall thickened at septum and apices when young, lumina quickly becoming rounded, spores later becoming waisted, pigmented band around each cell; torus: absent, walls: not ornamented Pycnidia: not seen Spot tests: all negative Secondary metabolites: zeorin. Substrate and ecology: on calcareous rocks World distribution: scattered in Scandinavia, mountains of southern and central Europe, North Africa, Australia, New Zealand, and western North America Sonoran distribution: southern California. Notes: Rinodina luridata is characterized by its small, Bicincta-type spores, its usually ochraceous and areolate thallus with innate to adnate apothecia. Rinodina luridata has been compared to R. lecanorina (A. Massal.) A. Mas-sal. by Mayrhofer et al. (1990), a species with larger spores, thicker thallus and larger apothecia that is not known from North America.