On a recent mushroom foray in Washington State we found a wonderful fungus that shows evolution in action. We now know that underground truffles started out as cup fungi fruiting on the surface of the soil, then retreated below as the climate dried out. This fungus, Geopora cooperi, shows the process part of the way through. What was once a large cup fungus has folded in on itself and become like a ball of scrunched up newspaper (look at the first picture), with the spore-bearing surfaces on the inside, as the second picture shows.
I had never seen this before and it was an exciting discovery for a mycologist/evolutionist. If you are fascinated by natural history and biodiversity, as I am, this shows that you never run out of new things to see and wonder at.