Knowra Crinoid Crinoid A marine echinoderm in the class Crinoidea, including stalked sea lilies and free-moving feather stars. Its feathery arms capture suspended food particles.
Echinoderm : A marine invertebrate in the phylum Echinodermata, typically with radial symmetry and a water vascular system. Crinoids are one of the five living echinoderm classes.
Suspension feeding : A feeding mode in which animals capture food particles suspended in water. Crinoids collect plankton and organic particles from passing water.
Crinoid fossil : The preserved remains or traces of a crinoid, often represented by stem segments or skeletal plates. Their durable calcite skeletons are common in marine fossil deposits.
Crinoid limestone : A limestone composed largely of fossil crinoid skeletal pieces, especially stem segments called columnals. Abundant crinoid debris can form conspicuous, identifiable sedimentary rock.
Asteroidea : The echinoderm class containing sea stars, typically with broad arms continuous with the central disk. Sea stars move and feed differently from crinoids with feathery arms.
Water vascular system : A fluid-filled canal system in echinoderms that powers tube feet and supports movement, feeding, or gas exchange. Crinoids use its canals in their arms and tube feet.
Pinnule : A small side branch extending from a crinoid arm, bearing tube feet and a food-gathering surface. Rows of pinnules increase the arm surface exposed to food-bearing currents.
Paleozoic : The geologic era from about 541 to 252 million years ago, marked by major diversification of marine life. Crinoids became abundant and diverse across Paleozoic seas.
Columnal : A disk-shaped segment of a crinoid stem, commonly preserved as a fossil. Columnals often identify crinoids even when the rest of the animal is absent.
Ophiuroidea : The echinoderm class containing brittle stars, characterized by slender, sharply distinct arms used for locomotion. Brittle stars have flexible locomotor arms rather than crinoid feeding fans.
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