Fossilized sea urchin tests. All are about ¾ – 1" in diameter.
Era: Cretaceous (70 million years ago)
The pictures are average representatives of our current inventory. You may not receive the ones pictured, but specimens like them. We attempt to prioritize the largest specimens to ship first.
Sea urchins appear to have first evolved about 450 million years ago during the Ordovician period. We know this thanks to their calcium carbonate shells, called tests, which are exceptionally well preserved through fossilization. This urchin likely belonged to the genus Goniopygus which places this specimen in the late Cretaceous period, which occured 70 million years ago.
Urchin larvae have bilateral symmetry (two halves of their tests look like mirror images), but they develop five-fold symmetry as they mature. You may be able to make out the five symmetrical sections of your fossil. The larger hole in the test would have been the urchin’s mouth, and it would have pointed down.