A derived characteristic that is found in vertebrates is the formation of neural crest cells. Neural crest cells are ectodermally derived, and develop along the top of the neural tube as the neural folds close. Most neural crest cells change into what is called mesenchyme, an embryonic tissue that consists of star-shaped cells from all three germ layers. The neural crest cells are extremely important to vertebrates and act in higher-level organization in the embryo. After the production of the nerve tube, differentiation of the germ layers occurs rapidly, and many new structures are formed.
All endodermal derivatives stem from the first endodermal derivative, the archenteron.
We have already discussed one of the first mesodermal derivatives, the notochord, which is derived from chordamesoderm. The mesodermal derivatives are extremely complex. These three blocks then differentiate into more structures. Lateral plate mesoderm separates into. The cleidoic egg is an important derived trait among many vertebrates, and enabled tetrapods to be independent of water.