Distribution: N - Ven (Lazzarin 2000b, Nascimbene 2008c), TAA (Nascimbene & al. 2007b), Lomb, Piem (Isocrono & al. 2004, Matteucci & al. 2008b), Emil, Lig. C - Tosc, Marc (Nimis & Tretiach 1999), Umb (Ravera 1998, Ravera & al. 2006), Laz (Ravera 2002b), Abr, Sar (Zedda 2002). S - Camp (Garofalo & al. 2010), Pugl, Bas (Potenza 2006, Potenza & Fascetti 2012, Ravera & al. 2021c), Cal (Puntillo 1996), Si.
Description: Thallus foliose to subcrustose, homoiomerous, gelatinous when wet, coarsey wrinkled and indistinctly lobed, forming rounded cushions to 1.5 cm diam., and to 1 cm thick when moist. Lobes short, flattened, adpressed, sometimes with lobules developing from wrinkles, dark olive-green to brown-black. Apothecia numerous, crowded, 0.8-1.5(-2) mm across, with a flat, brown disc, and a thick, more or less wrinkled thalline margin. Proper exciple thin, of thin-walled, slightly pigmented hyphae; hymenium and hypothecium colourless; paraphyses thin (1-1.5 µm), lax, branched, distinctly brown-pigmented at the slightly swollen apices. Asci (6-)8-spored, with a I+ reddish to blue wall, the tholus lacking amyloid structures. Ascospores 9-16-septate, hyaline, worm-like and spirally arranged in ascus, often attenuated towards one or both ends, (50-)70-120(-170) x 4.5-5 µm. Photobiont: cyanobacterial (Nostoc. Spot tests: all negative. Chemistry: without lichen substances.
Note: a mild-temperate lichen with a fragmented holarctic range, found on old broad-leaved trees, often on mosses in open, humid stands, somehow more frequent in the past, presently very much declining. With the probable exception of Liguria, it may be presently almost extinct in northern Italy, and could be restricted to a few humid sites of Tyrrhenian Italy. The recent record from Tuscany by Pasquinelli & Poccini (2010), judging from pictures and description, is wrong. The species is included in the Italian red list of epiphytic lichens as “Near-threatened” (Nascimbene & al. 2013c).