Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.

Life habit: lichenized, lichenicolous or parasymbiotic Thallus: crustose, verrucose to +areolate, sometimes with small peripheral squamules, thick or thin, superficial or immersed surface: gray to greenish gray, yellow, pale green or brown yellow cortex: 10-13 µm thick, formed by interwoven hyphae, sometimes interspersed with small yellow or colorless crystals photobiont: Trebouxia, or absent in lichenicolous species Ascomata: apothecial, almost immersed in thalline tissue or sessile; disc: black, at first almost closed, later open; margin: black, proper, with or without thalline rim true exciple: variable in thickness, laterally usually well developed, forming a distinct raised rim, rarely reduced laterally, blackish brown, sometimes white pruinose, formed of densely interwoven, sclerotized hyphae mazaedium: well developed, black; paraphyses: simple, thread-like, disintegrating asci: formed singly from ascogenous hyphae with croziers, at first clavate but becoming cylindrical or broadly clavate or obovate, thin walled, unitunicate, disintegrating at an early stage, the spores being released into a dry black powdery mass (mazaedium), 8-spored ascospores: dark brown, 1-septate with a slight or pronounced constriction at septum, rarely 3-septate to submuriform; wall: thick, smooth or with a distinctive ornamentation of irregular cracks or parallel ridges Conidiomata: pycnidial, spherical to slightly flattened or confluent to form irregular aggregates, 55-190 x 55-12 µm, at first semi-immersed in the thallus; ostiole: initially punctiform, later irregularly split; wall: 7-20 µm thick, in the lower part thinner, consisting of isodiametric or slightly elongated, hyaline cells c. 2-3 µm in diam.; in the uppermost part: wall cells spherical, 4-5 µm in diam., and heavily sclerotized, blackish brown; ontogeny: of the Umbilicaria-type; conidiophores: branched, type V of Vobis (1980); conidiogenous cells: ellipsoid to short cylindrical, 2-4 x 1.5-3 µm; conidia formed acrogenously and pleurogenously conidia: non-septate, hyaline; composed of two types (both often produced in the same thallus): 1) cylindrical, 3-4 x 1 µm, narrower towards one end; and 2) ellipsoid, 3-4 x 1.5 µm Secondary metabolites: pulvinic acid derivatives in yellow species, ß-orcinol depsides and depsidones and tetronic acid derivatives Substrate: on bark or wood, or rarely on rock or lichens, ecologically wide-ranging, with some species occurring in very dry and exposed sites and others in wet and humid habitats Geography: mainly Northern Hemisphere, in cool to temperate areas. Notes: Calicium is similar but has stalked apothecia. Thelomma differs in having the apothecia immersed in verrucae, with the lateral part of exciple very thin and hyaline, the basal part brown-black, very thick and cushion-like, and in most species non-septate spores. Both Cyphelium and Thelomma, however, are heterogeneous and not monophyletic in molecular phylogenies (unpublished).