Plagiopylida

The Plagiopylida are a small order of ciliate protozoa, including a few forms common in anaerobic habitats. The body cilia are dense, and arise from monokinetids with an entirely unique ultrastructure. One or two rows of dikinetids run into the oral cavity, which takes the form of a groove, with a deep tube lined by oral cilia leading to the mouth. The order was introduced by Small & Lynn in 1985, who treated it as a subclass of Oligohymenophorea. Since then they tend to be treated as an independent class, possibly affiliated with the Colpodea[?].