Description: This large, foliose, dark-grey to brown, dog lichen that attaches to the trunk and bases of mossy trees in old, undisturbed woodland like strips of Velcro has smooth lobes and bears horizontally-held oval to circular discs. It is distinctive when seen and occurs most frequently in woodland with a long history of continuous canopy, especially in western Ireland.

Key Identification Features:

• The reddish-brown fruits that are held more or less flat, strongly suggest this species
• The underside criss-crossed by dark (sometimes almost black) veins on a white background that support bundle rhizinae (root-like attachment structures) is diagnostic in material without discs.

Original text submitted by Simon Davey

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

iNaturalist: Peltigera horizontalis at iNaturalist World Species Observations database.