Crinoids are a class of the phylum Echinodermata that began in the Ordovician Period and were widespread during the Paleozoic. Stalked crinoids, which live connected to the sea floor, are commonly called "sea lilies" and filter nutrients from the water. Unstalked crinoids are known as "feather stars" and have a small body with arms that look like large bird feathers and are used to filter food from the water.

Courtesy of >Creative Commons; photo by James St. John