Choreotrichia Euplotia Hypotrichia Licnophoria Oligotrichia Phacodiniidea Protohypotrichia The spirotrichs are a large and diverse group of ciliate protozoa.

Forms with sparse or absent body cilia tend to be smaller and are mostly marine, but a few are common in freshwater.

As first defined by Bütschli in 1889 the spirotrichs were one of two orders, together with the now-abandoned holotrichs, and included all ciliates with prominent oral cilia: heterotrichs, hypotrichs, oligotrichs, and peritrichs, although the last were soon separated.

The heterotrichs have an adoral zone of membranelles, but molecular and ultrastructure studies have shown they are a separate group that diverged from most other ciliates early on.

However Halteria and its close relatives, originally considered oligotrichs, form a separate group and may even be modified stichotrichs.