Fossils are integral tools used to describe not only extinct species, but the evolutionary history of the species that live today. Already, we have learned so much about Earth’s biology from the fossil record. A few examples include the evolution of modern birds from small, feathered dinosaurs that scurried along the forest floor nearly 65 million years ago, and the development of vascular plant tissues during the Devonian, around 400 million years ago. The ability to date the origin of rock formations is one of the best qualities fossil evidence has to offer, because not only can we study the fine morphological details of past organisms, but we can understand when they showed up along Earth’s ancient history.
Unfortunately for us, not all of Earth’s past species are represented equally in the fossil record. In a perfect world, the 99% of species that have gone extinct before us would show up in pristine condition throughout the fossil record. We would be able to build extensive phylogenetic relationships by simply looking at rocks. It would be incredible, but you and I both know, we don’t live in a perfect world. We live in a world in which some organic structures are more easily fossilized while some rapidly deteriorate before sediments can settle and encase the deceased organism. Soft bodied fungi do not preserve well at all. As far as I know, there has only been one fossilized mushroom found in rock so far. That fossil was recently found in 2017, within Northeast Brazil and was later named Gondwanagaricites magnificus. It has been pristinely preserved for an estimated 113–120 million years.
The 113–120 million year old Gondwanagaricites magnificus.
The other ancient fungi we have uncovered have been preserved in amber. Luckily for us, organisms trapped in amber have their fine details preserved so there is much to learn from these specimens. Again in 2017, a wonderful ancient mushroom was found in Burma. This mid-Cretaceous, 99-million-year-old mushroom has all of its fine details preserved. Palaeoagaracites antiquus is its name and it was likely a saprotrophic or parasitic species that broke down dead/living plant material from these prehistoric trees.
Two researchers looked more closely at these preserved mushrooms in amber, and using powerful microscopes and imaging software, they actually found other fungal parasites breaking down the main specimen’s tissue. That’s right, fungus on fungus. These mushrooms preserved in amber really are a snapshot of a moment in time from an extremely distant era.
Mycoparasitism in Burmese amber. Hyphae (small arrows) of M. atrebora inside lamellar tissue of P. antiquus.
Another amber preserved specimen found in 2007 revealed an entirely different ecological role compared to other ancient fungi found. This particular fungus was actually a carnivore! Like many modern day nematode trapping fungi, this 100 million fossil from Southwestern France too utilized hyphal lassos that wrap around the bodies of these roundworms. These fungi then release digestive enzymes that break down these nitrogen rich animals.
A representation of ancient, carnivorous, nematode trapping fungi.
In 2011, David Hughes and his team discovered evidence of a fungal parasite from a fossilized leaf. This 48 million year old preserved leaf displays the telltale signs of a successful cordyceps infection. Even today, an ant infected by a cordyceps fungus will bit down on a leaf’s vein on the abaxial surface in its last act. This behavior is called the death grip, and it ensures the sexual structures of the fungus remain attached to the leaf long after the ant host has died. Even though there was no preserved fungus in this example, this fossilized leaf shows the presence of these ridiculously cool fungal parasites.
Fossilized death grip reveals the presence of cordyceps 48 million years ago.
These discoveries lead us to the notion that not only was fungal diversity high millions of years ago, but extremely complex fungal interactions where present. These interactions help shaped these ancient ecosystems from the bottom up. From decomposition rates, to mycoparasites to insect parasites, ancient fungi played integral roles and have clearly had their hand in shaping evolutionary trends.