part of part of in taxon develops from existence starts during produces Eumetazoa Chordata sonic hedgehog protein organ embryo stage multi-tissue structure neural tube digestive tract notochord The notochord appears early in embryogeny and plays an important role in promoting or organizing the embryonic development of nearby structures. In most adult chordates the notochord disappears or becomes highly modified. In some non-vertebrate chordates and fishes the notochord persists as a laterally flexible but incompressible skeletal rod that prevents telescopic collapse of the body during swimming[TOLWEB] ectoderm-derived structure chordamesoderm notochordal plate axial skeletal system