Crinoids, aptly nicknamed “feather stars”, can inhabit a wide range of marine environments and, judging by the fossil record, were very abundant organisms in the past, especially in the mid- to late-Paleozoic. They usually have a stem to attach themselves to a substrate but many only live attached as juveniles and spend most of their lives as free-swimming entities. They obtain nutrition by filtering small particles of food from the water using the mucous covered tube feet covering their feathery arms. Though they display the five-fold symmetry typical of echinoderms, some crinoids can have as many as two hundred arms!

https://en.wikipedia.org/wiki/Crinoid