My daily beach wanders usually turn up an interesting find or two. I stumbled across a fossilized Sea Biscuit (Clypeaster sp.) early on during my stay and the partial, contemporary one just recently.
I’m having difficulty pinning down an exact age for the fossil but they first enter the record during the Eocene (around 37mya). I suppose once your form has been perfected there is little reason to change it.
Note: The fossil is underside up, the other is top up. Also, I must content myself with just the photo, as Costa Rica prohibits the removal of any nature items from the country.