A lancelet is a small, fish-like marine animal belonging to the phylum Chordata and the subphylum Cephalochordata. They are known for their elongated, streamlined bodies and lack of a true backbone. Lancelets live in shallow coastal waters, burrowing into the sand and filtering food particles from the water. These creatures are significant in the study of evolution, as they share characteristics with early vertebrates. Lancelets possess a notochord, which is a flexible rod that provides support, and they have gill slits for respiration. Their simple body structure makes them a valuable model for understanding the development of more complex organisms.