Plagiopylida

{{Short description|Order of single-celled organisms}}

{{Automatic taxobox

| display_parents = 2

| parent_authority = Small & Lynn, 1985

| taxon = Plagiopylida

| authority = Jankowski, 1978{{cite book|title=The Ciliated Protozoa: Characterization, Classification, and Guide to the Literature | vauthors = Lynn DH |edition=3rd |publisher=Springer |isbn=978-1-4020-8239-9 |page=409|date=2008-06-24 }}

| subdivision_ranks = Typical families

| subdivision =

• Plagiopylidae
• Sonderiidae

}}

The plagiopylids are a small order of ciliates, 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 Eugen Small and Denis 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. Class Plagiopylea is divided into two clades:{{cite journal | vauthors = Boscaro V, Santoferrara LF, Zhang Q, Gentekaki E, Syberg-Olsen MJ, Del Campo J, Keeling PJ | title = EukRef-Ciliophora: a manually curated, phylogeny-based database of small subunit rRNA gene sequences of ciliates | journal = Environmental Microbiology | volume = 20 | issue = 6 | pages = 2218–2230 | date = June 2018 | pmid = 29727060 | doi = 10.1111/1462-2920.14264 | s2cid = 19135660 | url = http://ir.yic.ac.cn/handle/133337/24501 | url-access = subscription }} one contains members of the order Plagiopylida (like Plagiopyla frontata and Trimyema compressum) and the second clade contains plagiopylean ciliate associated with denitrifying obligate endosymbiont Candidatus Azoamicus ciliaticola.{{cite journal | vauthors = Graf JS, Schorn S, Kitzinger K, Ahmerkamp S, Woehle C, Huettel B, Schubert CJ, Kuypers MM, Milucka J | display-authors = 6 | title = Anaerobic endosymbiont generates energy for ciliate host by denitrification | journal = Nature | volume = 591 | issue = 7850 | pages = 445–450 | date = March 2021 | pmid = 33658719 | pmc = 7969357 | doi = 10.1038/s41586-021-03297-6 | bibcode = 2021Natur.591..445G }}