Featherstar, close-up. This marine invertebrate (also called a crinoid) is an ancient and primitive echinoderm, a member of the group of invertebrates that includes the starfish. It uses its feathery and fragile arms to catch and convey microscopic plankton and detritus to its mouth at the base of its arms. Unlike the closely-related sea lily, a featherstar is a free-swimming animal. Photographed off the island of North Sulawesi, Indonesia