Phytologia 28: 483 (1974).

Basionym: Lichen quercinus Willd., Fl. Berol. Prodr.: 353 (1787).

Protolog: Data lacking.

Protolog type data: Germany, Berlin, icon in Willdenow, Fl. Berol. Prodr.: 1787: P1. 7, Fig. 13 (Lectotype, Hawksworth et al., Lichenologist 43, 2011); Spain, Madrid, Aldea del Fresno, 2003 Argüello et al. (MAF-Lich 13946 epitype, Hawksworth et al., Lichenologist 43, 2011).

Type locality: Data lacking.

Type locality coordinates: Data lacking.

Molecular barcode: Data lacking.

Thallus: foliose, closely adnate, rosette-forming, dichotomously branched, to 8 cm diam., pale grey with a slightly bluish or olivaceous tinge, rather glossy, slightly maculate and partly pruinose. Lobes rounded, indented to entire, continuous, to 10 mm Wide, overlapping towards the centre; cilia sparse, marginal, black, to 1 mm long. Lower surface brownish black, pale towards the margin; rhizines common, simple, rarely squarrose, to 3 mm long. Apothecia common, slightly raised, strongly concave, with smooth edges, rhizinate on underside, to 5 mm diam.; disc brown. Spores ellipsoid, 6-12 x 4.5- 7 μm. Pycnidia irmnersed, black. Conidia slightly dumbbell shaped, 5- 8 x 1 μm.

Photobiont: Data lacking.

Chemistry: Cortex C-, K+ yellow, KC—, PD—; atranorin. Medulla C+ red, K—, KC+ red, PD—; lecanoric acid.

Ecology: On bark of deciduous trees, preferably on twigs of oak, in open woodlands.

Distribution type: Known from southern Danish islands and north-eastem Zealand, but has disappeared from all former localities. Common in southem Europe, extending to Macaronesia, northern Africa, Asia, California, Central America and Australasia.

Note: In the American literature, Parmelia quercina and Parmelia tiliacea have been used variously to refer to P. quercina, P. livida and P. galbina (W. L. Culberson 1961: 169 when synonymizing P. carporrhizans with P. querzina).