This exquisitely prepared 3-D fossil of an Uperocrinus nashvillae crinoid shows how the calyx and anal tube evolved to keep gastropods and others away. The spines are thought to impede or prevent such creatures from attaching to the calyx. Fossil was found in Iowa in Mississippian period rock.
Fossil photographed in 2010 at the Smithsonian National Museum of Natural History in Washington, D.C.
