a bilaterally symmetrical pelagic larva of the phylum Echinodermata. Development of the dipleurula results in the formation of the echinopluteus larva of sea urchins, of the ophiopluteus of brittle stars, of the bipinnaria and brachiolaria of starfishes, of the auricularia and doliolaria of sea cucumbers, and of the barrel-shaped larva of sea lilies. In structural design the dipleurula is similar to the tornaria of the phylum Enteropneusta and to the larvae of the phylums Pogonophora and Chaetognatha, which attests the phylogenetic kinship of these groups.