Hi, just joined the forum after browsing some very informative posts.
My wife and I found the items pictured on the beach on Oahu, Hawaii.
They appear to resemble others' pictures of porcupinefish dental plates. I have found info on similar finds from the Philippines, Australia, and Florida, but nothing from Hawaii.
What we are mainly wondering is whether these are fossilized or just hard due to being made of tooth material (we have not found any still attached to a jawbone).
Sorry about no coin in the photo for scale, the largest specimen is about 1 inch or 2.5 cm.
As we say in Hawaii, Mahalo for any insights!