1. Amphioxus is a small marine invertebrate that lives in sand and has a notochord but no distinct head or vertebral column. 2. It has gill slits for filtering food particles from water and an endostyle for processing food through the pharynx to the intestine. 3. Amphioxus spends much of its time buried in sand and uses rapid movements of its body and continuity of the notochord to burrow, and contracts its myomeres to swim side to side.