Cephalochordata (from
Greek: κεφαλή kephalé, "head" and χορδή khordé, "chord") is a
chordate subphylum defined by the presence of a
notochord that persists throughout life. It is represented in the modern oceans by the Amphioxiformes (
lancelets, also known as amphioxus). Along with its sister phylum
Urochordata, Cephalochordata can be classified as belonging to the taxon
Protochordata.