[2] This taxon was later (1875) transferred by Ferdinand Arnold into Imbricaria (a now obsolete genus name sunk into Anaptychia).

[7] Parmotrema arnoldii has a pale grey thallus comprising lobes that measure 6–15 mmm wide.

The lower surface of the thallus (the subthallus) is black to brown and has a naked marginal zone (i.e. without rhizines).

[8] Parmotrema arnoldii is widely distributed, and has been recorded from temperate locations in Africa, Asia, Europe, Oceania, Macaronesia, and North and South America.

Typically growing among mosses that associate with plants, often on old shrubs or horizontal tree branches, the lichen prefers relatively well-lit and humid undisturbed woodlands.