Notochord is unique to Chordata (it is a diagnostic feature) and is evident at some stage of the life cycle in all chordates.
An animal belonging to the phylum Chordata is a chordate. At some point during their larval or adult phases, all chordates have five synapomorphies, or primary traits, that set them apart from all other taxa.
The term "chordate" can be defined as "the class of animals that, at least throughout some stage of their development into adulthood, possess the following four anatomical features:
