5.5" Crinoid (Platycrinites) Fossil - Crawfordsville, Indiana

This is a 5.5" long Platycrinites hemisphericus crinoid from the bluff's site near Crawfordsville, Indiana. The crinoid crown is naturally associated with a gastropod (Platyceras). The quality of preparation on this fossil is exquisite - using skillful air-abrasion techniques under a stereo microscope.

This is a composite piece, meaning the stem and the crown are from two different crinoids. The stem is on it's original rock and the crown has been composited onto it.

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.

Platycrinites hemisphericus & Platyceras (Gastropod)
Bluff's Site, Crawfordsville, Indiana
Edwardsville Formation
Platycrinites 5.5" long (including stem), Rock 7 x 5.6"
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