Fossil fungi : At left are fossil hyphae from the Cretaceous of northern France. The filaments resemble those of the living genus Candida. At right is a Miocene perithecium from Nevada. The fine preservation is due to the silicification of chert in which it was embedded.

While fungi are not uncommon fossils, their fossils have not received a great deal of attention compared to other groups of fossils. Their fossils tend to be microscopic; very few large fungal bodies, such as mushrooms, have ever been found as fossils. Fossil fungi are often difficult or impossible to identify. The fungal filaments shown above at left are a case in point; found in Cretaceous amber from north France, they resemble living filaments of the common ascomycete Candida; however, since there is little information on how this fossil organism lived or how it reproduced (both important in recognizing modern taxa), its true affinities may never be known. By contrast, the Miocene fossil at right above has preserved the perithecium, an enclosed reproductive structure. Features of the spores and the perithecium in which they occur suggest that this may be a fossil species of Savoryella.

Recent careful studies of some well-preserved material have contributed much to our knowledge of fossil fungi. In particular, microscopic examination of fossil fungi from the Devonian-age Rhynie Chert in Aberdeenshire, Scotland, has shown that fungi and land plants were forming symbiotic relationships even at that very early stage in terrestrial evolution. In fact, all four major groups of modern fungi have now been found in Devonian strata, showing that the fungi had successfully invaded the land and begun to diversify before the first vertebrates crawled out of the sea!

More fossil fungi : At left is a section through a silicified stem of Aglaophyton from the Devonian Rhynie Chert. Among the cells are a fossilized fungus Paleomyces. At right are fungal spores from Lost Chicken Creek.

The oldest fossil fungi so far known are probably chytrid-like forms from the Vendian Period (Late Precambrian), found in north Russia. Older fossils of Precambrian "fungi" are now usually considered to be empty sheaths of filamentous cyanobacteria, or else are not distinct enough to be placed in any taxon with certainty. Fossil fungi older than the Devonian are rare; the fungi may have undergone an evolutionary radiation at about the same time that the land plants began to radiate.