裸唇纲是外肛动物门的一个纲。在海水中生活。分三个目。

• 栉口目（Ctenostomata）：例如：Bowerbankia。
• 唇口目（Cheilostomata）：例如：草苔虫、膜孔苔虫、裂孔苔虫等。
• 环口目（Cyclostomata）：例如：管孔虫（Tubulipora），栉苔虫（Crisia）等。近年来常将环口目提升为窄唇纲（Stenolaemata）。

Gymnolaemata are a class Bryozoans. Gymnolaemata typically live under seawater and grow on surfaces of rocks, kelps, and in some cases on animal species, like fish. They are mostly marine bryozoans with cylindrical or flattened zooids. The lophophore is protruded by action of muscles pulling on the frontal wall. This order includes the majority of living bryozoan species.