Editing Euglenid (section)

== Classification ==

[[File:Algen I. (Schizophyceen, Flagellaten, Peridineen) (1910) (17950163265).jpg|right|thumb|upright=1.2|Examples of euglenid diversity.<br/>1—2. ''Ascoglena'' sp. (Euglenales);<br /> 3–4. ''Cryptoglena'' sp. (idem);<br /> 5–9, 14–15, 24–25, 27–29. ''[[Trachelomonas]]'' spp. (id.);<br /> 10. ''Eutreptia'' sp. (Eutreptiales);<br /> 11, 20. ''Astasia'' spp. (Euglenales);<br /> 12. ''Distigma'' sp. (Eutreptiales);<br /> 13. ''Menoid[i]um'' sp. (Rhabdomonadales);<br /> 16–18. ''Colacium'' sp. (Euglenales);<br /> 19, 26. ''Petalomonas'' spp. (Sphenomonadales);<br /> 21. ''Sphenomonas'' sp. (id.);<br /> 22–23. ''Euglenopsis'' sp. (Euglenales);<br /> 30. ''[[Peranema]]'' sp. (Heteronematales)]]

The first attempt at classifying euglenids was done by [[Christian Gottfried Ehrenberg|Ehrenberg]] in 1830, when he described the genus ''[[Euglena]]'' and placed it in the Polygastrica of family Astasiae, containing other creatures of variable body shape and lacking [[pseudopod]]s or [[lorica (biology)|lorica]]. Later, various biologists described additional characteristics for ''Euglena'' and established different classification systems for euglenids based on nutrition modes, the presence and number of [[flagella]], and the degree of [[metaboly]]. The 1942 revision by A. Hollande distinguished three groups, Peranemoidées (flexible phagotrophs), Petalomonadinées (rigid phagotrophs) and Euglenidinées (phototrophs), and was widely accepted as the best reflection of the natural relationships between euglenids, adopted by many other authors.<ref name="Bicudo 2016">{{cite Q|Q57898656|doi-access=free }}</ref> Gordon F. Leedale expanded on Hollande's system, establishing six orders ([[Eutreptiales]], [[Euglenales]], [[Rhabdomonadales]], [[Sphenomonadales]], [[Heteronematales]] and [[Euglenamorphales]]) and taking into account new data on their physiology and [[ultrastructure]]. This scheme endured until 1986, with the sequencing of the [[SSU rRNA]] gene from ''[[Euglena gracilis]]''.<ref name="Bicudo 2016"/>

Euglenids are currently regarded as a highly diverse clade within [[Euglenozoa]], in the [[eukaryotic supergroup]] [[Discoba]].<ref name="Adl 2019">{{cite Q|Q57086550}}</ref> They are traditionally organized into three categories based on modes of nutrition: the [[phototroph]]s ([[Euglenophyceae]]), the [[osmotroph]]s (mainly the 'primary osmotrophs' known as [[Aphagea]]), and the [[phagotroph]]s, from which the first two groups have evolved.<ref name="Lax 2020">{{cite Q|Q101127864}}</ref> The phagotrophs, although [[paraphyletic]], have historically been classified under the name of [[Heteronematina]].<ref name="Adl 2019"/> 

In addition, euglenids can be divided into inflexible or rigid euglenids, and flexible or metabolic euglenids which are capable of '[[metaboly]]' or 'euglenid motion'. Only those with more than 18 protein strips in their pellicle gain this flexibility. Phylogenetic studies show that various clades of rigid phagotrophic euglenids compose the [[basal (phylogenetics)|base]] of the euglenid tree, namely [[Petalomonadida]] and the paraphyletic '[[Ploeotiida]]'. In contrast, all flexible euglenids belong to a [[monophyletic]] group known as [[Spirocuta]], which includes Euglenophyceae, Aphagea and various phagotrophs ([[Peranemidae]], [[Anisonemidae]] and [[Neometanemidae]]). The current classification of class Euglenida, as a result of these studies, is as follows:<ref name="Lax 2020"/><ref name="Lax 2021">{{cite Q|Q110667805}}</ref><ref name="Kostygov 2021">{{cite Q|Q125548575}}</ref><ref name="Lax 2023">{{cite Q|Q123348233}}</ref><ref name="Lax Keeling 2023">{{cite journal|vauthors=Lax G, Keeling PJ|title=Molecular phylogenetics of sessile ''Dolium sedentarium'', a petalomonad euglenid|journal=The Journal of Eukaryotic Microbiology|volume=70|number=e12991|date=2023|pages=e12991 |doi=10.1111/jeu.12991|doi-access=free|pmid=37424051}}</ref>
* Euglenida ''incertae sedis'': ''[[Atraktomonas]]'', ''[[Calycimonas]]'', ''[[Dolium]]'', ''[[Dylakosoma]]'', ''[[Tropidoscyphus]]'', ''[[Michajlowastasia]]'', ''[[Parastasiella]]'', ''[[Dinemula]]'', ''[[Paradinemula]]'', ''[[Mononema]]'', ''[[Ovicola]]'', ''[[Naupliicola]]'', ''[[Embryocola]]'', ''[[Copromonas]]''.
* Order [[Petalomonadida]] {{au|Cavalier-Smith 1993}}
* Order "[[Ploeotiida]]" {{au|Cavalier-Smith 1993}} (paraphyletic)
** Clade [[Alistosa]] {{au|Lax & Simpson 2021}}
** ''[[Entosiphon (excavate)|Entosiphon]]'' {{au|Cavalier-Smith, Chao & Vickerman 2016}}
** ''[[Gaulosia]]'' {{au|Lax, Cho & Keeling 2023}}
** Clade [[Karavia]] {{au|Lax, Cho & Keeling 2023}}
** ''[[Chelandium (genus)|Chelandium]]'' {{au|Lax, Cho & Keeling 2023}}
** ''[[Olkasia]]'' {{au|Lax, Lee, Eglit & Simpson 2019}}<ref name="Lax 2019">{{cite Q|Q92132357}}</ref>
* Clade [[Spirocuta]] {{au|Cavalier-Smith, Chao & Vickerman 2016}}<ref name="Spirocuta">{{cite Q|Q31135651}}</ref> [Helicales {{au|Perschke et al. 2017}}]<ref name="Lax 2021"/>
** Clade [[Anisonemia]] {{au|Cavalier-Smith 2016}}
*** Order [[Anisonemida]] {{au|Cavalier-Smith 2016}}
**** Family [[Anisonemidae]] {{au|Kent 1880 emend. Cavalier-Smith 2016}}
*** Order [[Natomonadida]] {{au|Cavalier-Smith 2016}}
**** Suborder [[Metanemina]] {{au|Cavalier-Smith 2016}}
***** Family [[Neometanemidae]] {{au|Cavalier-Smith 2016}}
**** Suborder [[Aphagea]] {{au|Cavalier-Smith 1993 emend. Busse & Preisfeld 2003}} [Rhabdomonadina {{au|Leedale 1967 emend. Cavalier-Smith 1993}}]<ref name="Higher Euglenozoa">{{cite Q|Q39151632}}</ref>
***** Family [[Astasiidae]] {{au|Kent 1884}}
***** Family [[Distigmidae]] {{au|Hollande 1942}}
** Order  [[Peranemida]] {{au|Bütschli 1884}}
*** Family [[Peranemidae]] {{au|Bütschli 1884}}
** Clade [[Euglenophyceae]] {{au|Schoenichen 1925, emend. Marin & Melkonian 2003}} [Euglenea {{au|Butschli 1884, emend. Busse & Preisfeld 2002}}]
*** Euglenophyceae ''incertae sedis'': ''[[Ascoglena]]'', ''[[Euglenamorpha]]'', ''[[Euglenopsis]]'', ''[[Glenoclosteroium]]'', ''[[Hegneria]]'', ''[[Klebsina]]'', ''[[Euglenocapsa]]''.
*** Order [[Rapazida]] {{au|Cavalier-Smith 2016}}
**** Family [[Rapazidae]] {{au|Cavalier-Smith 2016}}
*** Order [[Eutreptiales]] {{au|Leedale 1967, emend. Marin & Melkonian 2003}}
**** Family [[Eutreptiaceae]] {{au|Hollande 1942}}
*** Order [[Euglenales]] {{au|Leedale 1967, emend. Marin & Melkonian 2003}}
**** Family [[Phacaceae]] {{au|Kim et al. 2010}}
**** Family [[Euglenaceae]] {{au|Dujardin 1841, emend. Kim et al. 2010}}