It is a name that was given to chordate animals for their shape, since they are small marine invertebrates with spindle profile, head and tail finished as lancets. In Greek 945; 956; 966; 953; 959; 958; 959; 962; ( amphioxos ) is composed of 945; 956; 966; 953; ( amphi "both sides" ) 959; 958; 965; 962; ( oxys "pointed" ) .
In Biology it is an invertebrate living being, considered the first step of vertebrates. Instead of spine it has a cartilaginous cord. It is shaped like an elongated fish and lives in shallow water and is often buried in the mud. It feeds on plankton. It is also called lancet, acranius or leptocardium. It belongs to the subphyle Cephalochordata (cephalocordates).