Class Ascidiaceae is a group of marine animals also known as sea squirts or tunicates. These animals are known for their sac-like body structure and their ability to filter feed. There are several synonyms used to refer to Class Ascidiaceae including Tunicata, Urochordata, and Ascidiacea. Tunicata comes from the Latin word "tunica" meaning tunic or mantle, which refers to their unique body structure. Urochordata comes from the Greek words "oura" meaning tail and "chorda" meaning cord, referring to the notochord found in the larval stage. Lastly, Ascidiacea comes from the Greek word "askos" meaning wine skin, referencing the sac-like structure found in these unique marine animals.