Plural of leptocardium . In Biology they are invertebrate living beings, 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. They are also called lancets, acranons or amphiboxes. They belong to the subphyle Cephalochordata (cephalocordates).
