The dorsal nerve cord is one of the embryonic features unique to chordate

Chordate

Chordates are animals which are either vertebrates or one of several closely related invertebrates. They are united by having, for at least some period of their life cycle, a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail...

s, along with a notochord

Notochord

The notochord is a flexible, rod-shaped body found in embryos of all chordates. It is composed of cells derived from the mesoderm and defines the primitive axis of the embryo. In some chordates, it persists throughout life as the main axial support of the body, while in most vertebrates it becomes...

, a post-anal tail and pharyngeal slit

Pharyngeal slit

Pharyngeal slits are filter-feeding organs found in non-vertebrate chordates and hemichordates living in aquatic environments. These repeated segments are controlled by similar developmental mechanisms. Some hemichordate species can have as many as 200 gill slits...

s. The dorsal nerve cord is a hollow cord dorsal to the notochord.It is formed from a part of the ectoderm that rolls, forming the hollow tube, compared to other animal phyla, which have solid, ventral tubes. The dorsal nerve cord is later modified into the brain and spinal cord.
Dorsal nerve cord is mainly found in phylum Vertebrata.

Dorsal means the "back" side, as opposed to the belly side (ventral).

See also

• ventral nerve cord
  Ventral nerve cord
  The ventral nerve cord makes up the nervous system of some phyla of the invertebrates, particularly within the nematodes, annelids and the arthropods. It usually consists of cerebral ganglia anteriorly with the nerve cords running down the ventral plane of the organism...
  
   in arthropod
  Arthropod
  An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
  
  s
• nerve net
  Nerve net
  A nerve net is a type of simple nervous system that is found in members of the cnidaria, ctenophora, and echinodermata phyla. Nerve nets consist of interconnected neurons lacking a brain or any form of cephalization. This nervous system allows cnidarians to respond to physical contact. They may...
  
   in cnidaria
  Cnidaria
  Cnidaria is a phylum containing over 9,000 species of animals found exclusively in aquatic and mostly marine environments. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey. Their bodies consist of mesoglea, a non-living jelly-like substance,...
  
   and echinodermata phyla