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How many tunicate species are known?

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Bright blue sea squirt Rhopalaea crassa with yellow-edged openings grows on a coral reef among various corals in the Philippines. — tunicate Blue spot sea squirt (*Clavelina moluccensis*), a colonial tunicate.

There are approximately 2,600 known species of tunicates, which are members of the subphylum Tunicata (also known as Urochordata) within the phylum Chordata.12

These species are categorized into three primary classes:

Class Ascidiacea (sea squirts): This group comprises the majority of known species, with approximately 2,500 identified.2
Class Appendicularia (Larvacea): There are about 70 known species in this class.2
Class Thaliacea: This class also contains approximately 70 known species.2