The Thalicea comprise a class of marine animals within the subphylum Urochordata. Unlike their bottom-dwelling relatives the ascidians, thaliaceans are free-floating for their entire lifespan. There are three orders of Thaliacea: Pyrosomida, Doliolida, and Salpida. Pyrosomes are colonies of tiny zooids arranged around a central chamber called the cloaca. As the water exhaled by the zooids exits the cloaca through a common opening, the water movement slowly propels the pyrosome through the sea. Doliolids and salps...
