Cheilostome colonies are composed of calcium carbonate and grow on a variety of surfaces, including rocks, shells, seagrass and kelps.

The colony shapes range from simple encrusting sheets to erect branching and even unattached forms.

Cheilostomes first appeared in the Late Jurassic (Pyriporopsis) but diversified very slowly during the Early Cretaceous, with only 1 family known up to the Albian.

During the Late Cretaceous, cheilostomes diversified rapidly to reach a level of more than 20 families in the Maastrichtian, replacing cyclostomes as the dominant group of bryozoans.

[5] Though the Cretaceous–Paleogene extinction event had some impact on genetic diversity, the rapid diversification continued into the Eocene, then apparently reaching a plateau of about 50 families up to the Holocene.