Synonyms: Leptogium saturninum var. complicatum Anzi
Distribution: N - Frl, Ven (Caniglia & al. 1999), TAA (Nascimbene & al. 2007b), Lomb (Rivellini 1994, Tretiach 1996, Arosio & al. 2003, Dalle Vedove & al. 2004, Abramini & al. 2008, Ravera & al. 2021c), Piem (Isocrono & al. 2004), VA (Piervittori & Isocrono 1999), Emil (Fariselli & al. 2020). C - Marc, Umb (Genovesi & al. 2002, Ravera & al. 2006, 2006b), Abr (Olivieri & Pacioni 1996, Olivieri & al. 1997, 1997b, Loppi & al. 1999, Brackel 2015, Gheza & al. 2021). S - Bas, Cal (Puntillo 1996).
Description: Thallus foliose, broad-lobed, homoiomerous, slightly gelatinous when wet, rather loosely adnate, forming large, more or less regular rosettes 5-12 cm in diam. Lobes 5-10 mm wide, contiguous or more or less imbricate, with rounded, ear-like apices, 70-150 µm thick, firm and rigid when dry. Upper surface brown-black or dark lead-grey, greenish brown when moist, minutely and irregularly but conspicuously wrinkled and striate. Lower surface white-tomentose with long-celled hairs to 1-1.5 mm long, and tufts of pale rhizines. Upper cortex formed by a single layer of cells, inner part of thallus with loosely interwoven chains of Nostoc and hyphae. Apothecia usually abundant, especially in the central parts, lecanorine, laminal, immersed in the thallus at first, then prominent, 2-4 mm across, with a brown-red, shiny disc and a grey-brown, rather thin, usually rugose thalline margin. Asci 8-spored, cylindrical-clavate, the apex thick, with a I+ blue apical dome and a I+ blue annulus projecting downwardly. Ascospores muriform, hyaline, 16-24 x 8-10 µm. Pycnidia immersed, marginal to submarginal, 0.1-0.3 mm wide. Conidia bacilliform, with swollen apices, 4.3~5.5 x 1.3~1.6 µm. Photobiont cyanobacterial (Nostoc, in long chains). Spot tests: all negative. Chemistry: without lichen substances.
Note: on isolated tress with base-rich bark, especially Juglans, Fraxinus and Populus in humid valleys with a rather continental climate. It is included in the Italian red list of epiphytic lichens as “Near-threatened” (Nascimbene & al. 2013c).