Description. Thallus thick, dark grey, often brownish in places when moist, areolate; areoles to 0.60-0.90(-1.20) mm wide; surface plane or slightly verrucose, matt, sometimes with a whitish scale; margin determinate; prothallus lacking; vegetative propagules absent. Apothecia innate at first, remaining broadly attached, frequent, often contiguous, to 0.65-0.80 mm in diam.; disc dark brown becoming black, persistently plane until overmature, sometimes pruinose with whitish scale similar to thallus but thinner, best seen when moist; thalline margin concolourous with thallus, entire, persistent, ca. 0.10 mm wide, with brown cracks and/or flaking white scale. ApothecialAnatomy. Thalline exciple 90-120 µm wide laterally; cortex 5-20 µm wide laterally; epinecral layer 5-10 µm wide; crystals absent in cortex and medulla; cortical cells to 4.0-5.5 µm wide, pigmented or not; algal cells to 14.0-15.5 µm long; thalline exciple 120-150 µm deep below in a few apothecia; cortex to 60-80 µm deep when expanded below; proper exciple 10-15 µm wide laterally, expanded to 20-40 µm wide above; hypothecium hyaline or yellowish, inspersed, 60-110 µm deep; hymenium 90-120 µm high, not inspersed, paraphyses 2.5-3.0 µm wide, conglutinate, apices to 4.0-6.0 µm, pigmented brown, forming a dark brown or reddish-brown epihymenium, sometimes with an outer excreted layer 5-10 µm deep in places, similar to thallus; asci 70-85 x 20-24 µm. Ascospores 8/ascus, Type A development, Bischoffii-type, (18.5-)21.0-22.5(-25.0) x (10.5-)12.0-13.0(-14.0) µm, average l/b ratio 1.7-1.8, often inflated at transverse wall when immature, not more so in KOH, lumina initially with well defined canals, pigmented band around septum poorly developed, typically becoming parallel sided, slightly constricted when overmature; torus sometimes briefly evident in immature spores; walls usually ornamented. Pycnidia deep within thallus, highly gelatinized; conidiophore structure not detectable; conidia bacilliform, 4.0-5.0 x ca. 1.0 µm.
Chemistry. Spot tests all negative; secondary metabolites not detected.
Substrate and Ecology. Calcicolous, including limestone and gypsum, at elevations of 730-1615m.
Distribution. This species is scattered in the dry western states, with a Rocky Mountain distribution and outliers in North Dakota and Arizona. The map of Mayrhofer (1984a) shows a southern European distribution extending from Spain and North Africa to the Middle East.
Notes. Rinodina guzzinii is closely related to R. bischoffii, differing from it in the better developed thallus, and by the significantly larger spores which are parallel sided rather than ellipsoid at maturity. The spores are of the Bischoffii-type (Giralt 2001) and are similar to those of R. castanomelodes in their shape but are significantly larger and lack, or only possess a faintly pigmented band around the septum. The spores illustrated in Mayrhofer (1984a) retain the inflation around the septum and were placed in the Dubyana-type. They are probably not fully mature.
The spores of R. guzzinii, although slightly larger on average, are also very similar to those of the oro-arctic R. calcigena. The thallus of R. calcigena is never as robust as that of R. guzzinii and the apothecia of the former species are typically narrowly attached rather than broadly attached. In addition, the apothecia of R. calcigena are characteristically very symmetrical with narrow thalline margins which tend to become excluded as the disc becomes convex. The apothecia margins of R. calcigena are often brown, partly reflecting the presence of a confluent parathecial ring but also the thallus pigmentation. Thallus pigmentation may however be masked by a secreted epinecral layer. Rinodina calcigena is usually characterized by hymenial inspersion and lack of spore wall ornamentation, in contrast to the lack of inspersion and light wall ornamentation of R. guzzinii. The two species might be expected to have an overlapping distribution but as yet R. guzzinii has not been found in Canada and R. calcigena has not been collected south of the Canadian border.
Specimens examined. U.S.A. ARIZONA. Pinal Co., Boyce Thompson SW Arboretum, T.H. Nash 6237; Yavapai Co., 0.5 km N McGuireville, T.H. Nash 34148 (both ASU). COLORADO. Boulder Co., Hall Ranch, 3mi SW Lyons, W.A. Weber 92799 (COLO); San Juan Co., Mesa Verde, T.H. Nash 17970 (ASU). IDAHO. Jefferson Co., S.K. Rope (Rosentreter personal herb.). MONTANA. Gallatin Co., 9 km W Bozeman Pass, B. McCune 13719 (personal herb.). NORTH DAKOTA. Billings Co., 6.5 mi E Medora, C.M. Wetmore 45173 (MIN, SASK). SOUTH DAKOTA. Custer Co., Hell Canyon, C.M. Wetmore 6904b (MSC). WASHINGTON. Benton Co., Horse Heaven Hills, J. Ponzetti 1359 (McCune 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, typically thick but sometimes poorly developed, areolate, areoles up to 0.4-0.9(-1.2) mm wide, plane or slightly verrucate surface: dark gray, sometimes pale brown in places when moist, dull, sometimes with a whitish surficial scale; margin: determinate; prothallus: absent; vegetative propagules: absent Apothecia: innate at first, remaining adnate; frequent, often contiguous, up to 0.4-0.8 mm in diam. disc: dark brown becoming black, persistently plane until overmature, sometimes with whitish scale similar to thallus but thinner thalline margin: concolorous with thallus, entire and persistent, c. 0.1 mm wide, with brown cracks and/or flaking white scale; excipular ring: absent thalline exciple: 90-120 µm wide laterally; cortex: 5-20 µm wide laterally; epinecral layer: 5-10 µm wide; cortical cells: up to 4-7 µm wide, pigmented or not; algal cells: up to 14-17 µm in diam.; thalline exciple: 120-150 µm thick below in some apothecia; cortex: up to 60-80 µm thick, cellular proper exciple: 10-15 µm wide laterally, expanded to 20-40 µm wide at periphery hymenium: 90-120 µm tall, not inspersed, sometimes with an outer excreted layer 5-10 µm thick in places, similar to thallus; paraphyses: 2.5-3 µm wide, conglutinate, with apices up to 4-6.5 µm, pigmented brown, forming a dark brown or reddish brown epihymenium; hypothecium: hyaline or yellowish, inspersed, 60-100 µm thick asci: clavate, 70-85 x 20-24 µm, 8-spored ascospores: brown, 1septate, broadly ellipsoid, type A development, Bischoffitype, (17-)20.5-21.5(-25) x (10-)11.5-12.5(-14) µm, often inflated at transverse wall when immature, lumina initially with well defined canals, finally inflating and excluding canal, typically becoming parallel sided, pigmented band around septum poorly developed; torus: sometimes briefly evident in immature spores; walls: usually ornamented Pycnidia: thick within thallus, highly gelatinized conidia: bacilliform, 4-5 x c. 1 µm Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: on limestone and calcareous sandstone World distribution: southern Europe and North Africa, east to Afghanistan, North America (dry, western interior, North Dakota to Arizona) Sonoran distribution: infrequent in Arizona at elevations of 730-1070 m. Notes: Rinodina guzzinii is closely related to R. bischoffii, differing from it in the better developed thallus, and by the significantly larger spores that are parallel sided rather than ellipsoid at maturity. The spores of R. guzzinii, although slightly smaller on average, are also very similar to those of the arctic-alpine R. calcigena (Th. Fr.) Lynge but that species may not occur south of the Canadian border. Rinodina calcigena is usually characterized by hymenial inspersion and lack of spore wall ornamentation, in contrast to the lack of inspersion and the light wall ornamentation of R. guzzinii. Ir is a new species to North America.