Description: Thallus crustose to subleprose, thin, yellowish green (fading to pale yellow in herbarium), forming large patches delimited by a cottony, zonate, fimbriate, whitish prothallus with 4-5(-5.5)µm thick hyphae aggregated into distinct radiating strands, rarely forming a more or less continuous fringe. Soredia abundant, greenish, granulose, up to 25 µm in diam., often aggregated in up to 80 µm wide, elongated to rounded consoredia, developing directly from the prothallus, soon covering almost the entire thallus surface, giving it a subleprose appearance, Apothecia very rare, lecanorine, up to 1.3 mm across, with a pale yellowish brown to grey-brown, faintly to heavily white-pruinose disc, and a thick, raised, distinctly yellowish or whitish, ecorticate thalline margin. Thalline esciple filled by crystals; proper exciple colourless, up to 25 µm wide; epithecium with yellowish brown crystals dissolving in K; hymenium colourless, 40-90 µm high, K/I+ blue; hypothecium colourless, often inspersed with oil droplets. Asci 8-spored, clavate, very thin-walled, with a K/I+ blue, tall tholus penetrated by a faintly amyloid apical cushion, the wall K/I-, surrounded by a blue outer layer, Lecanora-type. Ascospores 1-celled, hyaline, ellipsoid, 11-14 x 6-9 µm. Photobiont chlorococcoid. Spot tests: thallus and soredia K+ pale yellow then brownish, C-, KC-, P+ pale yellow, UV-. Chemistry: usnic acid, atranorin, zeorin, and a set of unidentified terpenoids.
Note: On bark in humid deciduous forests. This is a sorediate, mostly sterile epiphytic species described from North America and firstly reported from Europe (Tønsberg 1999, Harris et al 2000), which has been often confused with sterile specimens of the mainly epilithic Haematomma ochroleucum var. ochroleucum. Both species, when sterile, are extremely similar, and also have a similar chemistry, as they produce atranorin, usnic acid, and zeorin, but L. thysanophora also contains a characteristic set of terpenoids (“thysanophora-unknowns”) and (at least in European specimens) lacks porphyrilic acid, which is present in H. ochroleucum (Kukwa and Motiejūnaitė 2005). Several earlier records of H. ochroleucum from the Alps could be referred to L. thysanophora.
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)