Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol 1.

Thallus: foliose, forming orbicular rosettes, up to 3 cm diam., growing on a well developed, black hypothallus that may extend beyond the margin lobes: contiguous, with raised margins, 3-4 mm wide and up 8 mm long upper surface: whitish or gray-blue to partly fawn-colored, scabrid or slightly pruinose isidia: granular to coralloid, predominantly marginal, sometimes black-tipped upper cortex: paraplectenchymatous, 40-50 µm thick Apothecia: fairly common, mostly central, up to 1 mm diam.; disc: red-brown to brown, conspicuous isidiate, with a thalline margin; exciple: subparaplectenchymatous, 30-40 µm thick; hymenium: primarily hyaline but brown above, partially I+ persistently deep blue (vicinity of the asci), 110-150 µm high asci: clavate to subcylindrical, with no internal amyloid, apical structures, 8-spored ascospores: simple, colorless, ellipsoid, 20-24 x 10-12 µm (with an epispore; otherwise 15-19 x 9-10 µm) Conidia: not seen Spot tests: thallus K-, C-, KC-, P+ orange, Secondary metabolite: pannarin. Substrate and ecology: mainly on trees, but also on mossy rocks, in moist habitats, mainly in forests, rarely above the forest limit World distribution: widespread in temperate regions of both Northern and Southern Hemispheres Sonoran distribution: fairly common in moist forests, and at the forest limit (to 3000 m) in the SE mountains of Arizona and along the Sierra Madre Occidental in Chihuahua, and in Baja California. Notes: It was previously confused with P. conoplea, from which P. tavaresii differs in having corticate coralloid isidia rather than decorticated, dorsiventral lobules of P. conoplea. Because of this P tavaresii is a less 'fuzzy'-appearing species.