All chordates, such as vertebrates, eel-like lancelets, and tunicates, or sea squirts, at some point in their lives have a flexible, rod-shaped nerve structure called a notochord in their backs.

Chordates include all animals with a notochord ... This form of locomotion was aided by the ridged structure notochords and early backbones, which is something all vertebrates share.

Together, the vertebrates, urochordates and lancelets (also known as cephalochordates) constitute the phylum Chordata ... Florida lancelet and compare its structure with the genomes of other ...