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

Life habit: lichenized Thallus: umbilicate, squamulose, subfruticose, foliose, gelatinous when wet surface: black, sometimes grayish pruinose, smooth, granulose, papillose, sometimes isidiate anatomy: ecorticate, heteromerous, with compact or loose central strand of periclinally arranged hyphae and reticulate anatomy at thallus periphery photobionts: primary one a chroococcoid cyanobacterium, secondary photobiont absent Ascomata: absent or present, apothecial, laminal on thallus or marginal, orbicular, immersed to semi-immersed, margin indistinct to distinct, with thalloid rim ontogeny: hemiangiocarpous, forming pycnoascocarps from ascogonia beneath pycnidia ascoma anatomy: exciple hyaline, hypothecium hyaline, epithecium pale brownish yellow asci: prototunicate, wall thin, non-amyloid, 8-spored ascospores: simple, ellipsoid, broadly ellipsoid or globose; 5-15 x 3-14 µm; walls: thin, occasionally thickened, hyaline Conidiomata: absent or present, pycnidia laminal or marginal, immersed conidia: ellipsoid or bacilliform, c. 3 x 1 µm Secondary metabolites: none detected Geography: cosmopolitan, in arid to semi-humid, tropical, subtropical and warm temperate regions Substrate: limestone and calcareous rock, rarely siliceous rock. Notes: Thyrea differs from Digitothyrea in having immersed to semi-immersed, small apothecia, in its sparsely or unbranched thalli and its type of ascoma ontogeny. Foliose species of Lichinella are similar in external appearance, but can be separated from Thyrea by their polysporous asci and thallinocarpous type of ascomata.