Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.
Thallus: erect-shrubby and compact, up to 5 cm long branching: richly anisotomic to isotomic dichtomously branched, divergent basal part: concolorous to branches or light brown branches: cylindrical to ±irregular; lateral branches: ±constricted at attachment points, ±deformed by the presence of foveoles or transverse furrows; apices: sparsely branched, thick, ±distinctly twisted and recurved, resembling skeletal fingers, especially when heavily sorediate segments: terete, ±sausage-like papillae: small, verrucous, ±sparsely and unevenly distributed tubercles and fibercles: absent fibrils: short (1-2 mm) spinulous, sparsely and irregularly distributed soralia: broad, larger than half of diameter of branches, plane to slightly excavate, irregular shape, arising initially from cortex, mainly on terminal branches and fibrils, often confluent and covering most of the extremities of the branches isidiomorphs: absent pseudocyphellae: absent cortex: thin (3-6%), shiny medulla: dense, unpigmented axis: usually thin, sometimes rose pigmented Apothecia: unknown Spot tests: K+ yellow turning red, C-, KC- , P + orangish yellow Secondary metabolites: salazinic (major) and bourgeanic (major) acids, rarely salazinc acid alone, or rarely salazinic and norstictic acids. Substrate and ecology: on bark, sometimes on wood, rarely on rock in the chaparral, oak woodland, oak-pine forests; mainly on Quercus sp., Pinus sp. and diverse schrubs between 0 and 650 m of altitude World distribution: southwestern Europe, Macaronesia, western North America and South America Sonoran distribution: coastal, southern California in the Channel Islands, and Isla Cedros in Baja California. Notes: The main diagnostic characters of U. esperantiana are its constricted branches at attachment points, its large and even soralia without isidiomorphs and the usual presence of bourgeanic acid.