https://en.wikipedia.org/wiki/Chordate
Chordates are animals possessing a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail for at least some period of their life cycles.
Taxonomically, the phylum includes the subphyla
Vertebrata, including mammals, fish, amphibians, reptiles, birds;
Tunicata, including salps and sea squirts; and
Cephalochordata, comprising the lancelets.
Members of the phylum Chordata are bilaterally symmetric, deuterostome coelomates, and the vertebrate Chordates display segmentation.
The phylum Hemichordata including the acorn worms has been presented as a fourth chordate subphylum, but it now is usually treated as a separate phylum.
It, along with the phylum Echinodermata, including starfish, sea urchins, and sea cucumbers and their kin, are the chordates' closest relatives