Among the first animals to possess this structure were the fish Haikouicthys.
Among the first animals to possess this structure were the fish Haikouicthys. Consisting of a core of glycoproteins enveloped by two helices of collagen fibers, it secretes the protein sonic hedgehog homolog, which is important in the development of neurons. It forms during (*) gastrulation by the epiblasts that comprise the floor of the amnion cavity, and it leads to the formation of the neural plate. Extending to the sphenoid bone, for 10 points, name this structure found in the embryos of all chordates, the precursor of the vertebral column.
Among the first animals to possess this structure were the fish Haikouicthys.
{notochord}