Shark-tooth pattern

Shark-tooth pattern 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 1,000 Bells.

Sharks lose and replace teeth all their lives, and their skeletons are made of cartilage that rarely fossilises. That is why teeth are often the only parts of ancient sharks that survive as fossils.