Fossil Crinoid (Macrocrinus) With Anal Tube - Indiana

This is a crinoid fossil (Macrocrinus mundulus) from the famous crinoid beds near Crawfordsville, Indiana. This crinoid was prepared using skillful air-abrasion techniques under a stereo microscope. It has a nice section of stem still attached and an exposed anal tube protruding from the top of the crown. The rock measures 3.1 x 2.5" and the crown of the crinoid is 1.75" with about 2.5" of stem.

The crinoid fossil has been remounted on the rock.

Crinoids from the Ramp Creek Limestone were likely 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.

About Crinoids