[5] Molecular studies revealed that this species occupies an isolated position within the cryptothecioid subclade, distinct from Arthonia radiata, supporting its recognition as a separate genus.

The internal structure includes a red-brown epithecium that turns grey or pale green in potassium hydroxide solution (K), a colourless hymenium 40–60 μm tall, and numerous paraphysoids.

In Europe, P. pruinata shows a preference for rain-sheltered, dry bark of tree trunks in nutrient-enriched situations, particularly favouring species such as Maple, Ash, and Oak.

It can become locally dominant on tree trunks and is occasionally found on wooden boards and dry stonework.

[8] In South America, P. longipseudisidiata has been documented in mountain forest habitats of Brazil, specifically in the Chapada Diamantina region, where it occurs at elevations of around 1,100 m (3,600 ft).