Thallus: foliose, up to 6 (-8) cm in diam., orbicular to somewhat irregular lobes: linear and discrete to somewhat irregular-flabellate and confluent to partly imbricate, 0.8-2 mm broad, ± flat to irregularly concave, prostrate upper surface: gray-brown to brown, usually with a ± complete pruina, isidiate isidia: sparse to abundant but often unevenly so, arising as spherical papillae, becoming cylindrical-coralloid and some at times growing into lobules upper cortex: scleroplectenchymatous medulla: white lower cortex: irregularly prosoplectenchymatous lower surface: white to pale tan, darkening only in old necrotic parts of the thallus or not at all, dull to weakly shiny; rhizines: soon blackening, squarrosely branched Apothecia: frequent, up to 3 mm in diam., sessile, the margin becoming crenate and eventually unevenly isidiate-lobulate ascospores: 27-36 x 12-17 µm Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: bark (esp. deciduous trees) or rock World distribution: western North America from the Black Hills to Colorado, Utah, New Mexico and Arizona Sonoran distribution: throughout Arizona at higher elevations in the mountains. Notes: This species is unique in the genus, characterized by the distinctive true isidia and the pale lower surface. Most of the sorediate species of Physconia can and do produce strongly isidioid soredia at times, especially in older specimens or older parts of a thallus, but these can be distinguished from the true isidia of P. elegantula by their clustering in old soralia patterns and their lack of a true cortex. One specimen exhibited more strongly isidioid propagules, some of which have become dorsiventral, therefore resembling the Asian species P. grumosa Kashiw. & Poelt, but the status of that species in North America is still being evaluated.