Crinozoa

The Crinozoa are a subphylum of echinoderms, marine invertebrates that typically have a cup-shaped body with five or more flexible arms. These arms are edged with feathery projections and contain reproductive organs, as well as tube feet used for sensory functions. Food particles are swept along open grooves on the tentacles to the mouth by cilia.1

While about 700 species of crinoids exist today, primarily in deep waters, thousands of extinct species are known. The distinctive internal skeletons of these fossilized crinoids, made of calcium carbonate, make them important index fossils from the Paleozoic Era. Crinozoa includes the class Crinoidea, which encompasses sea lilies and feather stars. Sea lilies are stalked and attached to the seafloor, resembling plants, while feather stars are free-moving.123