2.5" Fossil Crinoid (Eucalyptocrinus) Calyx - Indiana
This is a calyx of the crinoid Eucalyptocrinus magnus. It is Silurian in age (430 million years old) from the Waldron Shale of Indiana.
Crinoids, sometimes commonly referred to as sea lilies, are animals, not plants. They are echinoderms related to starfish, sea urchins, and brittle stars. Many crinoid traits are like other members of their phylum; such traits include tube feet, radial symmetry, a water vascular system, and appendages in multiples of five (pentameral). They first appeared in the Ordovician (488 million years ago) and some species are still alive today.