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 Thallus: crustose, often verrucose upper surface: pale green to bluish gray, rarely bright yellow to orange, continuous, dull cortex: absent, surface formed by a layer of loosely and irregularly arranged, globose cells photobiont: primary one a Trebouxia, secondary one absent lower surface: absent Ascomata: apothecial, usually several concentrically arranged on thallus, sessile with biatorine margin disc: pale to dark brown, sometimes pruinose, +round, flat to slightly convex; thalline exciple: absent; exciple: well-developed, hyaline, paraplectenchymatous hymenium: hyaline, hymenial gel I+ blue, K/I+ blue; paraphyses: thin, branched and anastomosing; hypothecium: pale to dark brown, well-developed asci: clavate, lecanoroid, with distinct tholus lacking differentially staining structure and distinct ocular chamber, I+ dark blue, K/I+ dark blue, 1-8-spored ascospores: hyaline, richly muriform, ellipsoid to ovoid, 20-120 x 7-30 µm Conidiomata: campylidial, sessile on thallus, usually composed of a pycnidia-like sockle on top of which a lobe-shaped structure is found conidia: hyaline, simple, short, ellipsoid to drop-shaped, often intermingled with small algal cells Secondary metabolites: a variety of dibenzofuranes (usnid acid, isousnic acid), didepsides (atranorin), depsidones (argopsin, pannarin), triterpenoids (zeorin), lichexanthones, and pulvinic acid derivates (vulpinic acid) Geography: pantropical Substrate: mostly leaves, but also found on bark. Notes: Species of Sporopodium are recognized by their continuous thallus with globose surface cells which produce a minutely pulveraceous appearance, their large, often pruinose apothecia with distinct margin, their anastomosing paraphyses and muriform ascospores, and especially their abundant campylidia with mussel-shaped lobe and distinct base, which produce ellipsoid to drop-shaped conidia associated with small algal cells. Species of this genus usually contain a wide array of secondary metabolites. Other crustose lichens with muriform ascospores and campylidial conidiomata differ from Sporopodium by their mostly dispersed, smooth thallus, that usually lacks the rich secondary chemistry typical of Sporopodium species.