ciliateprotozoa that have relatively uniform cilia over their body, and lack or only have a few prominent oral membranelles. Most of the major lines of ciliates are holotrichous. They do not form a natural group, so the term is now used only as a physical description, although it has appeared in many earlier classifications. They were one of two orders in the classification of ciliates introduced by Otto Bütschliin 1889:
In this system the spirotrichs included all ciliates that have prominent oral cilia, and the holotrichs all those that lack them. Later the peritrichs, as well as the
chonotrichs, were either given their own groups or considered unusual holotrichs. In 1974, de Puytoracand various other workers abandoned the holotrichs, dividing them into the classes Oligohymenophoreaand Kinetofragmophora. The latter have since been divided into several more classes, and the gymnostomes in particular have been split into several different groups.
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