Thuchomyces (sometimes mistakenly called “Thucomyces”) is a genus of Archean fossils from the Witwatersrand of South Africa, and is the earliest macroscopic land life known. The generic name derives from thucholite, the carbonaceous material which "Thuchomyces" is preserved in, and the Ancient Greek word "myces", meaning "fungus". The specific name, "lichenoides", derives from its similarity to some modern lichens.
Description.
"Thuchomyces" resembles modern columnar biomats, alongside certain lichens, however the latter are far more recent, only having appeared "at most" 300 million years ago, and therefore it almost certainly is not a lichen, or even a eukaryote at all. Some fossils have a round structure at their tip, interpreted as a diaspore, and these structures can also be observed in the rock surrounding the fossils. The internal structure of "Thuchomyces" consists of a network of hyphae, made of intensely branching cells possibly connected via anastomoses. The outer layer of the organism consists of highly agglutinated hyphae with a layer of loose tissue inside it, alongside a "central cord" observed in immature specimens which disappears with age. "Thuchomyces" columns are roughly 200–500 micrometers across, and reach a height of roughly 1 mm. "Thuchomyces" shares many similarities with the Paleoproterozoic "Diskagma", having a similar size and shape, alongside both forming dense palisades on paleosols. However it lacks the spines of "Diskagma" and has complex vertical partitions, alongside having rounded terminations instead of the cup-like tips of "Diskagma".
Paleoecology.
Taking into account various features such as ventifacts, the concentration of carbon-13 in the rock and other geological features, the sediments "Thuchomyces" is known from are interpreted as being a wind-blasted desert environment crossed by ephemeral streams, which was occasionally flooded. In addition another organism named "Witwateromyces conidiophorus", a possible actinomycete bacterium, was found associated with "Thuchomyces", possibly as a decomposer.