Cephalochordates are a group of marine animals that belong to the phylum Chordata. They are characterized by their elongated, fish-like bodies and possess a notochord, which is a flexible rod that provides support. Cephalochordates are often referred to as lancelets and are typically found buried in sandy or muddy substrates in shallow waters. These organisms have a simple body structure and lack a true backbone. They filter-feed by drawing water through their bodies, capturing small particles and plankton. Cephalochordates are important for understanding the evolution of vertebrates, as they share key features with early ancestors of fish and other vertebrate groups.