neurochord

A neurochord is a prominent strand of nervous tissue, essentially a nerve cord. This term can refer to the primitive central nervous system found in chordates like lancelets, or to the large longitudinal nerve fibers present in certain segmented worms.1

In the broader context of chordates, a defining characteristic is the presence of a dorsal nerve cord, which runs along the back of the animal. This nerve cord is a key feature that distinguishes chordates from other animal phyla. In some related groups, like hemichordates, a structure called a neurochord is also present, formed by an inpocketing of the epidermis and containing large nerve cells.23