Amphioxus, am fee AHK suhs, also called lancelet, is a small sea animal that lives in shallow water. It is a link between vertebrates and invertebrates. It has no distinct brain, but has a nerve cord running along its back that is somewhat like the spinal cord of animals with backbones. Instead of the hard, jointed backbone of the vertebrates, the amphioxus has an organ called the notochord. This is a fairly stiff rod of cartilage, found along the back just under the nerve cord. This primitive form of backbone makes the amphioxus more like a vertebrate than an invertebrate.