CRINOIDS are a type of echinoderm, which is a group of animals that includes starfish and sea urchins. Crinoids live only in seawater, and although uncommon today, they were very abundant in the geologic past. Crinoids have a stem that is attached to the seafloor with a holdfast and topped with a crown-shaped body, or calyx, which bears feathery arms. Although they are commonly known as "sea lillies," crinoids are NOT plants. The arms gather small food particles from the water and transfer them to a mouth at the top of the calyx. The crinoid skeleton is composed of hundreds of tiny plates that usually fall apart when the animal dies.
At least 22 species of crinoids lived as dwellers in the Silurian reefs of Wisconsin. Eight of these species, shown above, have been placed in the reef diorama. Some paleontologists have also interpreted ancient reef crinoids as bafflers.