Embryos of modern vertebrates form transient notochord structures during gastrulation. The chorda-mesoderm develops into the notochord. The dorsal hollow nerve cord is a hollow cord dorsal to the notochord. All lungfish demonstrate an uninterrupted cartilaginous notochord and an extensively developed palatal dentition. The hagfish skeleton comprises the skull, the notochord, and the caudal fin rays. The notochord is found ventral to the neural tube. In vertebrates, the notochord develops into the vertebral column. In most vertebrates, the notochord develops into secondary structures. During early embryonic development the endoskeleton is composed of notochord and cartilage. The lancelet notochord, unlike the vertebrate spine, extends into the head. Most craniates are vertebrates, in which the notochord is replaced by the vertebral column. A tube-like formation develops in the midline, called the notochord. Shh is secreted by the notochord. Chordoma is a rare slow-growing neoplasm thought to arise from cellular remnants of the notochord. It is the fibrous remnant of the notochord.