Crinoidea, also known as sea lilies and feather stars, are a class of marine invertebrate animals that belong to the phylum Echinodermata. This class encompasses a diverse group of organisms characterized by their distinctive appearance, including a mouth-oriented upward and a crown-like arrangement of feathery arms.
The crinoidea have an ancient evolutionary history, dating back to at least the Ordovician period, and are considered one of the oldest known groups of echinoderms. They are primarily sessile, attached to the seabed or other substrates by a stalk called a column, although some species are capable of limited mobility.
The body of crinoids is composed of a calyx, which contains the visceral organs, and a series of branching arms that radiate from the central disk. These arms are lined with numerous tube feet, which possess tiny pincers called cirri that aid in capturing food particles suspended in the water.
Crinoids are filter feeders, using their feathery arms to create currents that draw in nutrient-rich water and trap tiny organisms or organic matter for consumption. They primarily consume plankton, detritus, and small organisms that they capture with their specialized feeding apparatus.
Due to their fragility and sensitivity to environmental changes, crinoidea are typically found in deep-sea habitats, although some species also inhabit shallow waters. They have complex reproductive strategies, with both sexual and asexual reproduction occurring within the class. Fossil crinoids are extremely common, with numerous species having been recorded from various geological periods.
