Ahoy! Textladen post ahead!
Cordyceps is a parasitic fungus effecting ants and other insects. One particular species is Ophiocordyceps unilateralis, which effects ants in such a way as to alter their behavior.
The fungus, once it has infected a host, will cause its host to climb up high to a plant structure and latch on before dying. The fruiting bodies of the fungus then emerge from the ant’s head and spores are spread once the structure matures. Now, here’s where it gets really creepy. The cordyceps fungus is oddly specific, causing ants to latch onto plants “about 25 cm above the ground, on the northern side of the plant, in an environment with 94-95% humidity and temperatures between 20 and 30 °C.” according to wikipedia. In addition, workers from an infected ant’s colony can sense when an individual is infected and will carry it far from the rest of the colony to avoid infecting others.
Now, obviously, the fungus doesn’t effect mammalians (like this dog’s skull), birds, fish, reptiles, etc, but it’s freaky to think about something like this effecting something else. Hell, it’s freaky enough to think about it as it is. Nor would the structure still be there without anything to anchor to, so you’d never see it on a mere skeleton.
Still. Nature is scary.