Olfactores is a group, called a clade, in taxonomy. Taxonomy is the way scientists put living things in groups to show how they are related to each other. Olfactores is part of the phylum Chordata, animals with notochords. These are rods of tissue that form inside the developing embryo. In many organisms, the notochord helps the spine or nervous system grow, but some animals have only a notochord and no spinal bones. Olfactores contains Vetulicolia, Tunicata (Urochordata) and Vertebrata (also named Craniata). Most animals in Chordata are also in Olfactores. Only the animals in Cephalochordata are in Chordata but not Olfactores.