Eusthenopteron

Eusthenopteron is a standalone fossil: one piece completes it. Dig up fossils at the cracks on the ground, have Blathers assess them, then donate it to the museum or sell spares for 2,000 Bells.

Eusthenopteron was a lobe-finned fish from about 385 million years ago. The bones inside its fins match the arm bones of land animals, helping scientists trace how fish evolved legs.