Hypotrichea

Euplotes is a genus of ciliates in the subclass Euplotia. Species are widely distributed in marine and freshwater environments, as well as soil and moss. Most members of the genus are free-living, but two species have been recorded as commensal organisms in the digestive tracts of sea urchins.

Urostylida is an order of littoral ciliates. The taxonomy of the order is largely unresolved and still subject to scientific inquiry.