These lichens are typically found in calcareous outcrops in the Northern Hemisphere, with biodiversity centres in the Mediterranean basin, Central Asia, and arid regions of western North America.

The taxonomy of the genus remains complex, with several taxa awaiting more robust data for proper classification.

[3] Pyrenodesmia species have a crustose, epi- or endolithic thallus that is white, gray, or brown in colour.

The apothecia are zeorine or rarely biatorine in form, with brown, gray, or black discs and true exciples.

These lichens can be found in sunlit conditions from coast to alpine zones, with some species such as P. helygeoides growing on acidic siliceous boulders in water.