Lancelets are small, fish-like marine animals belonging to the subphylum Cephalochordata. They are characterized by their elongated, slender bodies and lack of a backbone. Lancelets live in shallow coastal waters, where they burrow into the sand and filter-feed on plankton and organic particles. These creatures possess a notochord, which provides structural support, and gill slits for respiration. Lancelets are considered important for studying the evolution of vertebrates, as they share key features with early ancestors. Their simple body structure makes them a valuable model for understanding the development of more complex organisms.