In Biology it is an invertebrate living being, considered the first step of vertebrates. Instead of spine they have a cartilaginous cord. They are shaped like an elongated fish and live in shallow water and are often buried in the mud. They feed on plankton. It is also called lancet, acranium or amphibox. It belongs to the subphyle Cephalochordata (cephalocordates). The word as such means "thin-hearted or flat"
