[1] Platismatia erosa reproduces primarily asexually through the production of isidia, which are small outgrowths on the thallus surface.

The lichen's upper thallus is light tan to ashy gray, becoming brown at the lobe margins, and has a broadly reticulately ridged and veined surface with pseudocyphellae (small pores).

[2] The lichen has been recorded from Japan, Taiwan, Java, Vietnam, Nepal, the Philippines, and Sikkim, and Tibet.

[3] More recent chemical analysis has also identified atranorin, caperatic acid, and an unidentified yellow pigment in P. erosa.

[2] Phylogenetic analysis has shown that P. erosa is closely related to P. norvegica, with the two species forming a strongly supported sister relationship.