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Cyrtocrinida (class Crinoidea, subclass Articulata) An order of crinoids in which the calyx consists of large radial plates and a single dorsal plate which is probably a modified column. The column is short or absent. The arms are short and stout and may completely cover the aboral surface of the animal when withdrawn. The order is restricted to hard substrata (e.g. hardgrounds and reefs), and is known from the Lower Jurassic to the present.