Encrinite is a type of limestone; this piece is dated to over 500 million years ago and contains fossils of crinoids. Crinoids are a type of echinoderm, related to starfish and sea urchins. Although crinoids belong to the animal kingdom, they are often called sea lilies due to their flower-like crowns and plant-like stalks. Unlike lily flowers, some sea lilies can shed their stalks or unhook themselves from the bottom to crawl or swim away from danger.
The rings and columns embedded in the stone are from crinoid stalks. Encrinite can be found throughout Europe and the Americas, including the Midwest! Millions of years ago, much of what is now Iowa was under a shallow sea populated with echinoderms, fish, corals, gastropods (slugs and snails), trilobites (arthropods distantly related to horseshoe crabs), cephalopods (a group that includes modern-day octopuses and squids), and many other animals. Their remains accumulated at the bottom of the ocean, cementing into layers over time to form sedimentary rock – limestone.