Fern fossil

The fern fossil is a stand-alone fossil introduced in that appears in all subsequent games except.

In
After donating the fossil in, its plaque in the museum will read:

"Originally, all plants on the planet were actually sea dwelling, but then they eventually spread to land. This fossilized fern is thought to be one of the very first plants to make this move to dry land. Reproducing via spores rather than seeds, it resembles modern ferns, though several yards taller."

Real-world information
In real life, a fern fossil is a fossilized fern.