Starfish, sea star, sea urchin, sea cucumber, serpent star, and sea lily {starfish} {echinoderm} (Enchinodermata) are deuterostomes, live in ocean, have radial symmetry, have central disc, have five to twenty arms, and have mouth on underside. Starfish have no ganglia and no circulatory, respiratory, or excreting system. Brachiopoda and Phoronida share common ancestor, from which Enchinodermata ancestors split. Hemichordata ancestors and Echinodermata and Pterobranchia ancestors split.
Starfish can pump water {water vascular system}, to move and to open prey.
Enchinoderms {sand dollar} (Clypeasteroida) (superorder Gnathostomata) (class Echinoidea) can be flat and circular, have spines, and have five-star patterns. They relate to sea stars, sea urchins, and sea cucumbers.
Enchinoderms {sea cucumber} (Holothuroidea) can have cucumber shapes, flexible bodies, and tentacles.
Enchinoderms {sea urchin} (Echinus) (class Echinoidea) can have shells, long spines, tube feet, and five movable mouth parts.
Enchinoderms {sea star} can have star shape and five or more arms with tube feet.
Euryale, Astrophyton, and Gorgonocephalus {basket star} have slender branched crossed arms.
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Date Modified: 2022.0225