Cephalochordata

noun plural

Ceph·​a·​lo·​chor·​da·​ta -ˌkȯr-ˈdät-ə  -ˈdāt-ə 

: a subphylum or other major taxon of the phylum Chordata comprising the lancelets and characterized by extension of the notochord to the anterior as well as to the posterior end of the body