Animals that at least at some stage in their development possess a stiff, rod-like structure running along their back, called a notochord.
Animals that at least at some stage in their development possess a stiff, rod-like structure running along their back, called a notochord. This includes all the vertebrates, in which the notochord has evolved into the spinal column. It also includes a small number of invertebrates, including the simple fish-like lancelets, sea squirts and hagfish.
This includes all the vertebrates, in which the notochord has evolved into the spinal column. It also includes a small number of invertebrates, including the simple fish-like lancelets, sea squirts and hagfish.