For 10 points, identify this phylum of marine animals possessing radial symmetry, examples of which include sea urchins and starfish.
One species from this phylum begins life in the bipinnaria stage, which is usually followed by a brachiolaria stage. Members of this phylum possess an opening to filter water called the madreporite, which is a feature of this phylum's water vascular system. The act of harvesting one class of organisms in this phylum is called "trepanging." This phylum is the second-largest grouping of deuterostomes after Chordata. For 10 points, identify this phylum of marine animals possessing radial symmetry, examples of which include sea urchins and starfish.
One species from this phylum begins life in the bipinnaria stage, which is usually followed by a brachiolaria stage.
Echinodermata [or echinoderms]