Chordate unranked clades

Olfactores is a clade within the Chordata that comprises the Tunicata (Urochordata) and the Vertebrata (sometimes referred to as Craniata). Olfactores represent the overwhelming majority of the phylum Chordata, as the Cephalochordata (with only 32 known species across 3 genera) are the only chordates not included in the clade. This clade is defined by a more advanced olfactory system which, in the immediate vertebrate generation, gave rise to nostrils.