Earliest lichen

Lichens are compound organisms, consisting of a symbiotic association between a fungus and an alga and/or cyanobacteria, but they are named and classified according to their fungal constituents. The earliest lichen presently known from the fossil record is Winfrenatia reticulata, a crustose cyanolichen which dates back approximately 400 million years, to the early Devonian Period. It was found in the Rhynie Chert – a sedimentary deposit containing exceptionally well-preserved, plant, fungus, lichen and animal material – named after the village of Rhynie in Aberdeenshire, Scotland, which is nearby. The age of the lichen is discussed in a paper in the Paleontological Journal published on 7 February 2009.

Winfrenatia consists of a main body or thallus that is composed of layered fungal filaments called hyphae and has several depressions on its upper surface that house photosynthetic cyanobacteria (blue-green algae). Its fungal component seems most closely related to zygomycote fungi, and its algal component seems most closely related to certain coccoid cyanobacteria. Moreover, there may be two different algal types associated with the fungus, which if so means that Winfrenatia is a three-partner lichen rather than the usual two-partner version.