When did fungi first appear on earth?

The oldest fossil fungi so far known are probably chytrid-like forms from the Vendian Period (Late Precambrian)(650 to 543 Million Years Ago), 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.

http://www.ucmp.berkeley.edu/fungi/fungifr.html