Crinoids are marine animals that are part of the phylum Echinodermata, which makes them relatives to starfish, sea urchins, and sea cucumbers. One of our oldest fossils, crinoids have lived in oceans since at least the Ordovician Era (485 million years ago). These fragments were part of their tube-like stem, which served as their water vascular system. Crinoids were surprisingly resilient. They survived the Permian Period, which ended with the largest mass extinction event in history, and recent fossil discoveries suggest that these flower-like creatures may have even crossed seas by attaching themselves to driftwood. They flourished to their peak during the Mississippian period, when the shallow, marine environments they preferred were widespread on several continents.