Marsupella profunda, the western rustwort,[2] is a liverwort native to Europe and known only from Portugal (Mainland, Azores and Madeira) and Great Britain (Cornwall) and has been sighted in the Canary Islands.

[3] Marsupella profunda is a saxicolous plant, commonly found on open but shady sites, in wet rock crevices or on slopes.

[4][5][6] Within Cornwall, western rustwort is generally found growing on micaceous or clay waste substrates which are flat or gently sloping.

It appears to be a pioneer species, the largest populations being found on surfaces showing the early stages of colonisation by other bryophytes and by vascular plants.

[3] It disappeared from at least six Cornish sites between 1971 and 2005 due to shading from European gorse (Ulex europaeus) and bramble (Rubus fruticosus agg.