Thallus: umbilicate, mono- or polyphyllous, very irregular in outline, +deeply incised (lobate) with undulating, often ascending margins, thin, brittle, 2-4 cm in diam. upper surface: brown to gray-brown or almost black, smooth, +shiny medulla: white lower surface: black, smooth to minutely papillate, dull, covered in multicellular thalloconidia Apothecia: rare, black, sessile, gyrose, up to 1.5 mm in diam. asci: clavate, 8-spored ascospores: hyaline, simple, ellipsoid to broadly ellipsoid, 10-15 x 6-8 µm Thalloconidia: dark brown, ball-shaped, multicellular (412 cells), released directly from lower cortex Spot tests: medulla K-, C+ red, KC+ red, P- Secondary metabolites: gyrophoric, lecanoric, and umbilicaric acids. Substrate and ecology: on siliceous rocks and boulders in the boreal or low alpine zone, usually under snow in winter World distribution: Europe, Asia, Africa, Australia and North and South America Sonoran distribution: scattered on the high peaks of Arizona and southern California in the upper conifer to alpine vegetation zones. Note: Unlike most Sonoran Umbilicariae, U. polyphylla is typically polyphyllous with multiple lobes. Its smooth, brown upper surface and black lower surface with multicellular thalloconidia further distinguish it.