Type. AUSTRIA. TIROL. Kalkhornstein auf dem Kaiserjoch, nördlich ober Pettneu am Arlberg, 29/8/1892, F.C.G. Arnold s.n. (M - holotype!, isotype Mayrhofer (1984)). R. bischoffii var. castanomelodes (H. Mayrhofer & Poelt) Giralt & Llimona, Mycotaxon 62: 186 (1997).
Description.Thallus thick when fully developed, dark grey, or ochraceous to brown, areolate; areoles to (0.40-)0.80-1.40 mm wide, margins becoming subsquamulose and sometimes slightly lobed; surface rugose, usually shining, rarely matt; margin determinate or indeterminate; prothallus lacking; vegetative propagules absent. Apothecia erumpent at first, remaining broadly attached or becoming narrowly attached, frequent, contiguous or not, to 0.40-0.90 mm in diam.; disc black or pruinose, persistently plane or becoming convex, often fissured in largest apothecia; thalline margin concolourous with thallus, 0.05-0.10 mm wide, entire, persistent; excipular ring sometimes present, confluent. Apothecial Anatomy. Thalline exciple 70-120 µm wide laterally; cortex 5-20 µm wide; epinecral layer 5-15 µm wide; crystals absent from cortex and medulla; cortical cells to 5.5-7.0 µm diam., pigmented; algal cells to 14.0‑25.0 µm long; thalline exciple 110-140 µm wide below when apothecia narrowly attached; cortex not expanded; proper exciple hyaline, 10-20 µm wide laterally, expanding to 15-35 µm above; hypothecium colourless, 70-100 µm deep; hymenium 80-120 µm high, inspersed; paraphyses 2.0-3.5 µm wide, conglutinate, apices to 5.0-7.0 µm diam., heavily pigmented, forming a dark brown epihymenium; asci 65-80 x 20‑28 µm. Ascospores 8/ascus, Type A development, Bischoffii-type, (16.0-)18.0-19.0(-21.0) x (9.5-)11.0-11.5(-13.0) µm, average l/b ratio 1.6-1.7, canals quickly becoming excluded as lumina inflate, parallel sided to slightly constricted at maturity, pigmented band around septum narrow and usually not well developed; torus lacking; walls lightly ornamented. Pycnidia not observed.
Chemistry. Spot tests all negative; secondary products not detected (Hecklau et al. 1981).
Substrate and Ecology. Calcicolous rocks including basalt, recorded at 1,000-2 300 m.
Distribution. The species belongs to the Rocky Mountain element with scattered occurrences from Colorado north to Montana. Also found in the European Alps, Spain, rare in southern Europe, and always growing at high elevations according to Giralt (2001).
Notes.Rinodina castanomelodes is similar to R. bischoffii and R. calcigena in its Bischoffii-type spores but typically has a better developed thallus than either, the brown thalli of European material being reminiscent of R. castanomela although the areole margins are less well developed and do not become truly squamulose. Rinodina castanomela is not closely related, being separated by its Bicincta-type spores.
The spores are a similar size to those of R. bischoffii, although large spores of R. castanomelodes are parallel sided at maturity, rather than the ellipsoid shape of large spores of R. bischoffii, and its lumina canals are less persistent. Rinodina castanomelodes has a better developed thallus, larger apothecia with more persistently plane discs until late in development, and more prominent thalline margins compared to R. bischoffii. In addition, R. castanomelodes often has a shining thallus and sometimes a confluent excipular ring around the apothecial disc, both characters being absent in R. bischoffii. Despite these apparently distinct differences young specimens of R. castanomelodes with poorly developed thalli are difficult to separate from R. bischoffii, one reason why this species has been treated as a variety of R. bischoffii (Giralt 2001). The holotype of R. kansuensis (= R. straussii) is accompanied by both species on a uniform substrate. Viewed side by side in this manner there can be little doubt that the two species are distinct, despite the fact that no statistical difference in spore dimensions or shape could be demonstrated.
Rinodina calcigena has significantly longer spores than R. castanomelodes which often have lumina with relatively elongate canals when young and with a poorly developed pigmented band. In addition, the spores of R. calcigena are truly ellipsoid rather than parallel sided as already pointed out by Mayrhofer and Sheard (1988). Rinodina castanomelodes is apparently restricted to semidesert habitats in the centre of the continent whereas R. calcigena is an oro-arctic species. Rinodina guzzinii is a closely related species with similar parallel sided Bischoffii-type spores. The spores are, however, significantly larger and the thallus has a matt, scale like surface rather than the shining surface of R. castanomelodes caused by the epinecral layer which is well developed in North American collections, and which tends to hide the brown colour of the cortical cells.
Specimens examined. U.S.A. COLORADO. Boulder Co., 3 mi SW Lyons Hall Ranch, 1997, W.A. Weber (COLO). IDAHO. Twin Falls Co., Hageman Fossil Beds Nat. Mon., B.D. Ryan 32815, 32879, 32893 (ASU). MONTANA. Beaverhead Co., Pioneer Mountains, B. McCune 20673 (personal herb.); Dawson Co., 0.5 mi E Glendive, T.D. Trana 4662 (MIN); Flathead Co., Blacktail Hills, B. McCune 15231; Glacier Co., East Flattop Mountain, B. McCune 15920; Powell Co., Cramer Creek, B. McCune 6876 (all personal herb.).
Selected References. Mayrhofer & Poelt (1979), Mayrhofer (1984a), Giralt (2001 as R. bischoffii var. castanomelodes).