Thallus episubstratic, irregular in outline, to 2 cm in diam., small to medium-sized, persistent, rimose-areolate; margin simple, indistinct; surface dirty white to whitish grey, exposed parts gets a blackish tinge, rough and scabrous, matt; hypothallus poorly developed, visible at thallus margin only, black or white. Apothecia sparse, to 1.2 mm in diam., semi-immersed to sessile, slightly constricted; disc initially slightly concave, becoming plane to convex, ferruginous brown or ferruginous red, when shaded dark orange, occasionally with a dark brown almost blackish tinge, biatorine, but with algae at the very base; margin distinct to prominent, persistent or occasionally becoming excluded, occasionally flexuose, darker than remaining thallus surface, ferruginous brown or ferruginous red, orange when shaded, concolourous with or darker than disc, smooth, excipulum brownish. Subhymenium hyaline. Hymenium 60-90 μm high, hyaline; paraphyses with ramifications, terminal cells simple, to 3 μm wide, hyaline; epihymenium distinct. Asci clavate, to 70 × 20 μm. Ascospores 6-8 per ascus, ellipsoid to broadly ellipsoid, (12-)14-16 × 6-8 μm; spore septum 4-5 μm.
SECONDARY METABOLITES: apothecia: 7-chloroemodin (24%), 7-Cl-citreorosein (1%), 7-cl-emodinal (4%), fallacinal (3%), parietinic acid (3%), emodin (7%), and parietin (50%); chemo syndrome C4; thallus: atranorin. All reddish or brownish parts K+ red, C+ red. Thallus K+ yellow.
SUBSTRATE AND ECOLOGY: on sandstone. Habitat exposed to sun or partially shaded.
NOTES: The new species, C. scabrosa resembles the saxicolous C. crenularia in having a greyish, crustose thallus with ferrugineous apothecia. It is characterized by the distinct rimose-areolate and relatively thick, up to 0.9 mm, thallus, which is more whitish and has a very rough, scabrous to granulose surface. The apothecia differ in the darker and more reddish, flat to strongly convex disc that has a pronounced tendency to blacken at exposure, and by not having very flexuose apothecial margin. It has the same chemosyndrome as C. furfuracea and C. herbidella, except that atranorin has not been found in the thallus of those species; furthermore, C. furfuracea has more well developed, less scabrous thallus surface. Atranorin is a rare compound in Teloschistaceae, but occurs in the thallus of e.g. C. sinapisperma. C. scabrosa is known only from the type collection.