Chordate, << KAWR dayt, >> is the name of a large phylum (group) of land, marine, and freshwater animals. Chordates include lancelets, amphibians, fish, reptiles, birds, and mammals. At some time during their life cycle, all chordates have a notochord (a rodlike, flexible cord that runs down the back of the body). In vertebrates, the notochord is surrounded or replaced by a bony structure called a vertebral column. Chordates also have a hollow nerve tube that runs above the notochord. Chordates are segmented in some way, and they have left and right sides that are alike. Chordates also have gill slits, but in many cases these appear only during the undeveloped stage. See also Vertebrate.
