Discovering the world of fossil fungi

Violeta de Anca Prado and Stephen McLoughlin (Sweden) When people think of fossils, they usually picture slabs of rock bristling with bones, or the shells of ammonites or trilobites. Most do not even consider that delicate organisms, such as fungi or bacteria, can even fossilize – they seem too fragile to be preserved as they lack a hard skeleton. In many cases this is true. Microscopic organisms that lack hard parts have fewer chances of being fossilised but, despite the odds, delicate fungi have a fossil record that is more extensive than generally thought. The fossil record of fungi goes all the way back to the Proterozoic. Identifying the oldest fossil fungus is difficult because many reports of early fungi have later been reinterpreted as filaments of green algae or cyanobacteria. Nevertheless, increasing reports of fungi from the late Proterozoic are consistent with DNA comparisons (the so-called “molecular clock” method) that suggests fungi, plants and animals diverged about 1,600 million years ago. What is more certain, is that fungi were actively diversifying in terrestrial habitats as soon as plants gained a foothold on land. Fungi are fossilised in diverse styles. Usually, the best examples are preserved inside permineralized (petrified) wood or peats. The process of permineralization involves the organic tissues becoming entombed within mineral matter (usually calcium carbonate or silica), which is precipitated from solution in groundwaters. More rarely, we encounter fungi preserved as impressions, which are like a “fingerprint” of the organism – the original fungus has decayed but … Read More