As a result of this development, the neural processes and the costal processes are formed in the paraxial space from the dense caudal halves of the sclerotomes, i.e. from one pair of somites each. They are connected to the cranial areas of the vertebral centra. The vertebral centra and the intervertebral discs develop in the axial perinotochordal space. Formation of a vertebral centrum involves two somitic pairs. All elements of the vertebral column develop in situ and so displacement or resegmentation is not necessary.