Tintinnids are ciliates of the choreotrich order Tintinnida, distinguished by vase-shaped shells, the name deriving from a Latin source meaning a small tinkling bell, that are called loricae, which are mostly protein but may incorporate minute pieces of minerals.

[3] Tintinnids are an important part of the fossil record because of the rarity with which most other ciliates become preserved under the conditions of the marine environment.

[6] Many species appear to have wide distributions (for example from the Chesapeake Bay to New Caledonia) while others are restricted to certain areas, such as arctic waters or coastal seas.

They feed on phytoplankton (algae and cyanobacteria) and in turn act as food for larger organisms such as copepods (small crustaceans) and larval fish.

The cilia generate a water flow across the mouth of the cell, bringing food into contact and move the tintinnid.