Description: This is an extremely rare crustose epiphyte of isolated parkland trees and trees of the wayside. It has been in decline in Britain for decades and is a rarity also in Ireland with six pre–1970 records. There are few lichenologists alive that have seen its pink-yellow-brown, thickly warted thallus. In the herbarium, it tends to fade to grey and in this condition it may resemble Pertusaria pertusa (described elsewhere). However, T. modesta differs in its muriform spores, four-to eight-spored asci and lack of chemistry, that is, negative spot tests.

Key Identification Features:

• Thallus of living specimens pink or yellow-brown with wart-like discs
• No lichen substances, spores four to eight/ascus, muriform.

Original text submitted by Vince J. Giavarini

Distribution Map from NBN: Thelenella modesta at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Thelenella modesta at iNaturalist World Species Observations database.