Thallus: foliose, adnate to loosely adnate, 3-15 cm in diam., lobate; lobes: subirregular, elongate, slightly imbricate, plane, separate, 5-20 mm wide; apices: rotund, becoming crenate and dissected with age, sometimes ascending, ciliate; cilia: up to 3.0 mm long; upper surface: gray with some blackened areas, smooth, dull to shiny, epruinose, emaculate, finely reticulately cracked with age; isidia: simple to coralloid branched, sometimes disintegrating with age, often apically ciliate, common, laminal and marginal; soredia and pustulae: absent; medulla: white with continuous algal layer; lower surface: black with brown naked zone peripherally, centrally rhizinate, rhizines simple, black; Apothecia: rare, substipitate, up to 8 mm in diam.; margin: sparsely isidiate; disc: brown, imperforate; ascospores: ellipsoid, 21-35 x 11-18 µm; Pycnidia: not seen; Spot tests: upper cortex K+ yellow, C-, KC-, P-; medulla K+ yellow turning orange, C-, KC-, P+ orange; Secondary metabolites: upper cortex with atranorin and chloroatranorin; medulla with stictic acid (major) and constictic acid (minor), menegazziaic acid (trace).; Substrate and ecology: usually on hardwood trees in open habitats, rarely on rocks or soil; World distribution: pantropical and pantemperate; Sonoran distribution: SE Arizona southwards along the Sierra Madre Occidental in Chihuahua, Baja California and in the mountains of southern Baja California Sur. 

Canada

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

United States

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

In Great Britain and/or Ireland:
Lichen / pathogen
clustered pycnidium of Lichenoconium coelomycetous anamorph of Lichenoconium erodens infects and damages bleached or necrosed thallus of Parmotrema crinitum

Lichen / parasite
sporodochium of Marchandiomyces anamorph of Marchandiomyces corallinus parasitises bleached thallus of Parmotrema crinitum

Canada

Rounded National Status Rank: NNR - Unranked

United States

Rounded National Status Rank: NNR - Unranked

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: "Parmeliopsis crinitum can be found on trees and, less commonly, on rock in the open woods in eastern United States. In West Virginia it appears to be most common in the upland areas of the state" (Flenniken 1999).