N. Amer. Fung., 7, 2: 3, 2012. Basionym: Parmelia crozalsiana B. de Lesd. ex Harm. - Lich. de France, 4: 555, 1910.
Synonyms: Canoparmelia crozalsiana (Harm.) Elix & Hale; Parmotrema crozalsianum (Harm.) D. Hawksw.; Pseudoparmelia crozalsiana (Harm.) Hale
Distribution: N - Lig (Castello & al. 1994, Brunialti & Giordani 2000, 2003, Giordani & al. 2001, Giordani & Incerti 2008, Ravera & al. 2021c). C - Laz (TSB 17670). S - Si (Ottonello & al. 1994, Iacolino & Ottonello 2006).
Description: Thallus foliose, heteromerous, dorsiventral, adnate, sorediate, forming 3-8(-12) cm wide rosettes. Lobes irregularly rounded, (2-)3-5(-8) mm wide, pale to dark grey, reticulately ridged to slightly rugose, emaculate or faintly maculate, shallowly foveolate, epruinose or rarely slightly pruinose especially along the margins, cracked in older parts, with laminal, often capitate soralia developing along ridges and cracks; soredia white, granular to farinose. Lower surface black in central parts, with simple, black, to 1.5 mm long rhizines; marginal parts brown, erhizinate. Upper cortex of tightly packed, anticlinally oriented hyphae, with a pored epicortex; medulla white, also below the soralia; algal layer continuous; lower cortex prosoplectenchymatous, with rounded and thick-walled cells. Apothecia extremely rare, lecanorine, up to 3.5 mm across. Asci 8-spored, Lecanora-type. Ascospores 1-celled, hyaline, ellipsoid, 8-13 x (4) 6-8 µm. Pycnidia very rare, black. Conidia thread-like. Photobiont chlorococcoid. Spot tests: upper cortex K+ yellow, C-, KC-, P+ yellow; medulla K+ yellow-red, C-, KC-, P+ orange. Chemistry: cortex with chloroatranorin and atranorin; medulla with stictic, constictic and cryptostictic acids.
Note: a mild-temperate species with subtropical affinities, also reported from North America, locally abundant only - and strangely - in Liguria (especially in Olea-plantations), but also sporadically occurring in other warm-humid areas of Tyrrhenian Italy. It is included in the Italian red list of epiphytic lichens as “Endangered” (Nascimbene & al. 2013c). See also note on C. carneopruinata.
Growth form: Foliose, broad lobed
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)