[3] This lichen is characterised by its grey, areolate thallus that produces abundant lichenised diaspores, such as short spherical isidia and coarse, dark brown-black soredia.

Its habitats include weathered wooden structures influenced by nitrate enrichment, and while it is largely found in European mountain ranges and reported in New Zealand and South Africa, recent findings also place it in Tasmania, suggesting a broader distribution than previously thought.

Catillaria fungoides and overgrown Buellia griseovirens share certain visible traits with P. ocellatum, like dark pigmented soralia, but differ in substrate preference and chemical composition, respectively.

[8] Pseudothelomma ocellatum has a crustose (crust-like) thallus that is well-developed, with either a mosaic-like pattern (areolate) or elevated, coarse, and flattened warts, typically coloured grey.

The lichen is characterised by frequent isidia, which are small, outgrowth propagules that form irregular but well-defined clusters of blue or brown-black colour, generally slightly raised (convex).

[6] Chemical spot tests on the thallus yield negative results (C–, K–, Pd–, UV–), suggesting the absence of secondary metabolites (lichen products).

[11] Overgrown forms of Buellia griseovirens also somewhat resemble P. ocellatum due to the presence of a white thallus with what appears to be dark brownish-black soredia.

[12] However, the report of norstictic acid-deficient populations of Buellia griseovirens in the Yukon of Canada indicates that the chemical variability in this species is greater than previously suspected.

[18] In 1995, McCune and Rosentreter noted that the species is rarely found west of the Cascade crest in Oregon and Washington and is absent from the extreme coastal regions.

In California, the lichen seems to be prevalent in the northeast part of the state and becomes less frequent moving southward, occurring sporadically in both the Sierra foothills and the Coast Ranges.

Hardwood hosts include species such as Purshia and Robinia, while its coniferous partners encompass Abies, Juniperus, Larix, Pinus, Pseudotsuga, and Thuja.

The occurrence of this community, particularly in France, is commonly observed on wooden substrates like old vineyard stakes or abandoned agricultural wood, suggesting these lichens play a role in the ecological succession of these areas post-cultivation.