Type. U.S.A. NORTH DAKOTA. Billings Co., Theodore Roosevelt National Park, Cathedral Ridge, on Artemisia cana, 6 July 1959, R.L. Dix 1 (WIS - holotype!).
Illustration. Sheard & Mayrhofer (2002 Fig. 20).
Description.Thallus thin, light grey to ochraceous, areolate; areoles discrete or contiguous, sometimes with raised margins and minute marginal lobes, to 0.50‑0.60 mm wide, or forming a more continuous, rimose‑areolate thallus; surface plane or rugose, matt; margin indeterminate; prothallus absent; vegetative propagules absent. Apothecia broadly attached, frequent but rarely more than two per areole, to 0.40‑0.55 mm in diam.; disc dark brown to black, sometimes pruinose (most visible when moist), plane becoming convex; margin concolourous with thallus, 0.05‑0.10 mm wide, entire and persistent or becoming excluded; excipular ring absent. Apothecial Anatomy. Thalline exciple 60‑110 µm wide laterally; cortex 10-15(-30) µm; epinecral layer ca. 10 µm wide; crystals absent in cortex and medulla, cortical cells to 5.0‑7.0 µm wide, pigmented or not; algal cells to 15.0‑24.0 µm long; thalline exciple sometimes expanded to 90-120 µm below; cortex ca. 20 µm wide; proper exciple hyaline, 5-10 µm wide laterally, expanded to 20‑25 µm above; hypothecium colourless, (30-)50-70 µm deep; hymenium 80‑110 µm high, not inspersed; paraphyses 2.5‑3.5 µm wide, not conglutinate, apices expanded to 5.0‑7.0 µm, pigmented light brown, immersed in a dispersed, light blue-grey pigment in fresh material, with a weak K+ violet reaction developing slowly, forming a bluish grey, light grey-brown or dark brown epihymenium; asci 55-70 x 16-19 µm. Ascospores 8/ascus, Type A development, Beltraminia-type, (14.0-)17.5-18.5(-22.0) x (6.5-)8.0‑9.0(-10.5) µm, average l/b ratio 2.0-2.2, walls thin, equally thickened, narrow pigmented band at septum, very restricted swelling at septum in some immature and overmature spores in KOH; torus absent; walls not ornamented. Pycnidia open, pale; conidia bacilliform, 6.0-7.0 x ca. 1.0 µm.
Chemistry. Spot tests all negative; secondary metabolites not detected.
Substrate and Ecology. Collected on the steppe shrubs Sarcobatus vermiculatus, Artemisia cana, A. tridentata, and Atriplex confertifolia at elevations of 775-1,950 m, and rarely on sandstone. This inconspicuous species of the dry western interior is probably under collected.
Distribution. A North American endemic, probably belonging to the Colorado Plateau element.
Notes. The Beltraminia-type spores, broad paraphyses apices and weak K+ violet reaction of the epihymenium of fresh material, characterize R. lobulata. The algal cells and conidia also are unusually large for the genus Rinodina. The spores of R. lobulata are similar to those of Rinodinella species in their lack of wall thickening and predominantly narrowly ellipsoid, if somewhat variable shape (CV for both length and breadth >10%), but are more darkly pigmented. The very slight septal thickening shown in might suggest the spores belong to the Physconia-type but apical thickening has not been seen at any developmental stage. The nature of the narrow, pigmented septal band is unresolved. It might possible suggest a relationship with the Bischoffii-type spore.
Rinodina lobulata does not appear to be related to other corticolous species with a blue-grey epihymenium reacting K+ violet (Ropin & Mayrhofer 1995) because of differences in spore structure. Rinodina colobina is also easily distinguished by its dark blastidia and smaller, Dirinaria-type spores.
Two saxicolous, arid zone species with blue-grey epihymenium and spores with unthickened walls are R. zwackhiana (Kremp.) Körb. and R. athallina H. Magn. Rinodina zwackhiana possesses a thick, brown and sometimes sorediate thallus, and broadly ellipsoid spores which show evidence of separation of wall layers at the septum in early developmental stages (Sheard 1982). The spores of this species are here considered to belong to the Bicincta-type, despite their lack of pigmented bands around the cells. Rinodina athallina has a very variable, grey thallus but can be recognized by its much larger, narrowly ellipsoid, Beltraminia-type spores averaging >22.5 x 9.5 µm. Rinodina lobulata, due to its spore type and shape, may well be related to R. athallina.
Specimens examined [not reported by Sheard and Mayrhofer (2002)]. U.S.A. COLORADO, Mesa Co., Loma, D.D. Awasthi (COLO). IDAHO. Lemhi Co., SW of Tendoy, 1999, H. Mayrhofer (SASK). NEVADA. Churchill Co., near Dixie Valley, 1979, R.W. Stack (ASU); Pershing Co., 3 mi ESE Colado, B.D. Ryan 13074 (ASU). NORTH DAKOTA. Billings Co., T. Roosevelt Nat. Park, R.L. Dix 2, 3, 13 (WIS).