Squamules: up to 10 mm wide, rounded, adnate and dispersed to adjacent or imbricate, usually weakly to strongly concave; upper surface: orange to bright red or pink, more rarely reddish brown, dull, partly to entirely pruinose, sparingly fissured; margin: concolorous with upper side or white, down-turned or more rarely straight, more or less entire; upper cortex: up to 80-140 μm thick, composed of thin-walled hyphae with round lumina, containing crystals of calcium oxalate but no lichen substances; medulla: containing crystals of lichen substances and calcium oxalate; lower cortex: absent or poorly developed; lower surface: white to pale brown; Apothecia: up to 2 mm diam., marginal, immarginate even when young, black, epruinose or white pruinose; ascospores: 12-16 x 6-8 μm; Pycnidia: unknown; Spot tests: upper cortex K-, C-, KC-, P-; medulla K+ red, C-, KC-, P+ orange (in North America); Secondary metabolites: norstictic acid (in North America) or unknown chemotypes (southern Africa and Australia).
Pink to reddish squamules are diagnostic for P. crenata, P. decipiens and P. saviczii. Psora crenata differs from the other species in forming larger squamules with a more regular central depression and a more down-turned and entire margin. In North America where P. crenata and P. decipiens have overlapping distributions, they are chemically distinct: the former contains norstictic acid and the latter is acid deficient. In the Arctic and in the mediterranean Europe, however, a norstictic acid chemotype of P. decipiens occurs. In southern Africa and Australia the two species are apparently sympatric and several chemotypes occur, most of the compounds are still not identified. The taxonomy of the P. crenata/decipiens-complex in southern Africa and Australia is still poorly understood.
Psora saviczii is a Eurasian species which does not contain lichen substances. It has a paler pink thallus than that of P. crenata and P. decipiens, and is otherwise similar to P. decipiens.
Southern Africa, Australia, and southwestern North America.
On soil in open habitats, from deserts to juniper-pinyon pine woodlands, up to 1680 m alt.
Psora decipiens, Psora saviczii
