Dinosaur egg

The Dinosaur Egg is a standalone fossil in the introduced in  that appears in all subsequent games except.

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

"Dinosaur eggs vary in size depending on the species, but larger ones can reach about a foot in length. If the egg was fossilized when it was just about to hatch, sometimes intact bones can be found inside. However, it is generally rather difficult to determine the exact species a fossilized egg belongs to."