This is a 1" long, uncommon Abrotocrinus unicus crinoid from the famous Witherspoon crinoid quarry near Crawfordsville, Indiana. The quality of preparation on this fossil is exquisite - using skillful air-abrasion techniques under a stereo microscope.
It is believed that crinoids from the Ramp Creek Limestone were buried in sediment from nearby deltas during storms. The resulting siltstone deposits are soft enough that fossils
can be extracted in exquisite, three-dimensional relief.
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.