[3] The characteristics of a fossilized Phyllopsora, P. dominicana, found in Dominican amber, suggests that the main distinguishing features of the genus have remained unchanged for tens of millions of years.

[4] The genus was circumscribed by the Swiss botanist Johannes Müller Argoviensis in 1894, with Phyllopsora breviuscula assigned as the type species.

The proposal argued that conserving Phyllopsora would be the least disruptive option, as taking up Triclinum would require 56 new combinations, while Crocynia included many species now considered to belong to other genera.

[7] The genus Phyllopsora is distinguished by its scale-like (squamulose) to almost leaf-like (foliose) body (thallus) that often has a distinct border (prothallus).

The ascospores produced by Phyllopsora are small, with thin walls, and are typically not divided into separate compartments (rarely septate).