View source for Foraminifera

{{short description|Phylum of amoeboid protists}}
{{Use dmy dates|date=March 2022}}
{{automatic taxobox
| fossil_range = {{fossil range|542|0|ref=<ref name="Parfrey2011">{{cite Q|Q24614721}}</ref>}} Latest [[Ediacaran]]–Recent
| image = Ammonia tepida.jpg
| image_caption = Live ''[[Ammonia tepida]]'' (Rotaliida)
| taxon = Foraminifera
| authority = [[Alcide d'Orbigny|d'Orbigny]], 1826
| subdivision_ranks = Subdivisions
| subdivision = "[[Monothalamea]]"
* "[[Allogromiida]]"
* "[[Astrorhizida]]"
* [[Xenophyophorea]]
* ''[[Reticulomyxa]]''
[[Tubothalamea]]
* [[Miliolida]]
* [[Spirillinida]]
* [[Silicoloculinida]]
[[Globothalamea]]
* [[Textulariida]]
* [[Rotaliida]]
** [[Globigerinida]]
* [[Carterinida]]
* [[Robertinida]]
* [[Fusulinida]]? – ''extinct''

''incertae sedis''
* [[Involutinida]]
* [[Lagenida]]
}}

'''Foraminifera''' ({{IPAc-en|f|ə|ˌ|r|æ|m|ə|ˈ|n|ɪ|f|ə|r|ə}} {{respelling|fə|RAM|ə|NIH|fə|rə}}; [[Latin]] for "hole bearers"; informally called "'''forams'''") are [[unicellular organism|single-celled organisms]], members of a [[phylum]] or [[class (biology)|class]] of [[Rhizaria]]n [[protist]]s characterized by streaming granular [[Ectoplasm (cell biology)|ectoplasm]] for catching food and other uses; and commonly an external shell (called a "[[Test (biology)|test]]") of diverse forms and materials. Tests of [[chitin]] (found in some simple genera, and ''[[Textularia]]'' in particular) are believed to be the most primitive type. Most foraminifera are marine, the majority of which live on or within the [[seafloor sediment]] (i.e., are [[benthos|benthic]], with different sized species playing a role within the [[macrobenthos]], [[meiobenthos]], and [[Benthos|microbenthos]]),<ref>{{Citation|last1=Binczewska|first1=Anna|title=Foraminifers (Benthic)|date=2014|url=https://doi.org/10.1007/978-94-007-6644-0_60-1|encyclopedia=Encyclopedia of Marine Geosciences|pages=1–8|editor-last=Harff|editor-first=Jan|place=Dordrecht|publisher=Springer Netherlands|language=en|doi=10.1007/978-94-007-6644-0_60-1|isbn=978-94-007-6644-0|access-date=2021-05-13|last2=Polovodova Asteman|first2=Irina|last3=Farmer|first3=Elizabeth J.|editor2-last=Meschede|editor2-first=Martin|editor3-last=Petersen|editor3-first=Sven|editor4-last=Thiede|editor4-first=Jörn}}</ref> while a smaller number float in the water column at various depths (i.e., are [[plankton]]ic), which belong to the suborder [[Globigerinina]].<ref>{{Citation|last=Kimoto|first=Katsunori|title=Planktic Foraminifera|date=2015|url=https://doi.org/10.1007/978-4-431-55130-0_7|work=Marine Protists: Diversity and Dynamics|pages=129–178|editor-last=Ohtsuka|editor-first=Susumu|place=Tokyo|publisher=Springer Japan|language=en|doi=10.1007/978-4-431-55130-0_7|isbn=978-4-431-55130-0|access-date=2021-05-13|editor2-last=Suzaki|editor2-first=Toshinobu|editor3-last=Horiguchi|editor3-first=Takeo|editor4-last=Suzuki|editor4-first=Noritoshi}}</ref> Fewer are known from freshwater<ref>{{Cite journal|date=2017-08-01|title=Taxonomic revision of freshwater foraminifera with the description of two new agglutinated species and genera|journal=European Journal of Protistology|language=en|volume=60|pages=28–44|doi=10.1016/j.ejop.2017.05.006|issn=0932-4739|last1=Siemensma|first1=Ferry|last2=Apothéloz-Perret-Gentil|first2=Laure|last3=Holzmann|first3=Maria|last4=Clauss|first4=Steffen|last5=Völcker|first5=Eckhard|last6=Pawlowski|first6=Jan|pmid=28609684|doi-access=free}}</ref> or brackish<ref>{{Citation|last1=Boltovskoy|first1=Esteban|title=Benthonic Foraminifera of Brackish, Hypersaline, Ultrasaline, and Fresh Waters|date=1976|url=https://doi.org/10.1007/978-94-017-2860-7_5|work=Recent Foraminifera|pages=139–150|editor-last=Boltovskoy|editor-first=Esteban|place=Dordrecht|publisher=Springer Netherlands|language=en|doi=10.1007/978-94-017-2860-7_5|isbn=978-94-017-2860-7|access-date=2021-05-13|last2=Wright|first2=Ramil|editor2-last=Wright|editor2-first=Ramil}}</ref> conditions, and some very few (nonaquatic) soil species have been identified through molecular analysis of small subunit [[ribosomal DNA]].<ref>{{cite book|last=Giere|first=Olav|title=Meiobenthology: the microscopic motile fauna of aquatic sediments|year=2009|publisher=Springer|location=Berlin|isbn=978-3540686576|edition=2nd }}</ref><ref name="Lej">{{cite journal|last1=Lejzerowicz|first1=Franck |last2=Pawlowski |first2=Jan |last3=Fraissinet-Tachet |first3=Laurence |last4=Marmeisse |first4=Roland |title=Molecular evidence for widespread occurrence of Foraminifera in soils|journal=Environmental Microbiology|date=1 September 2010|volume=12|issue=9|pages=2518–26|doi=10.1111/j.1462-2920.2010.02225.x |pmid=20406290|bibcode=2010EnvMi..12.2518L |s2cid=20940138 }}</ref>

Foraminifera typically produce a [[test (biology)|test]], or shell, which can have either one or multiple chambers, some becoming quite elaborate in structure.<ref name=Kennett>{{cite book |first1=J.P. |last1=Kennett |first2=M.S. |last2=Srinivasan |title=Neogene planktonic foraminifera: a phylogenetic atlas |url=https://books.google.com/books?id=wr4TAQAAIAAJ |year=1983 |publisher=Hutchinson Ross |isbn=978-0-87933-070-5}}</ref> These shells are commonly made of [[calcium carbonate]] ({{chem|CaCO|3}}) or [[agglutination (biology)|agglutinated]] sediment particles. Over 50,000 species are recognized, both living (6,700–10,000)<ref>{{Cite journal|last1=Pawlowski|first1=J.|last2=Lejzerowicz|first2=F.|last3=Esling|first3=P.|date=2014-10-01|title=Next-Generation Environmental Diversity Surveys of Foraminifera: Preparing the Future|url=https://www.journals.uchicago.edu/doi/10.1086/BBLv227n2p93|journal=The Biological Bulletin|volume=227|issue=2|pages=93–106|doi=10.1086/BBLv227n2p93|pmid=25411369|s2cid=24388876|issn=0006-3185}}</ref><ref name="adl2007">Ald, S.M. ''et al''. (2007) [https://wayback.archive-it.org/all/20110331223739/http://myweb.dal.ca/jmarchib/2007.Adl.Syst.biol.pdf Diversity, Nomenclature, and Taxonomy of Protists], ''Syst. Biol.'' 56(4), 684–689, DOI: 10.1080/10635150701494127.</ref> and [[fossil]] (40,000).<ref>Pawlowski, J., Lejzerowicz, F., & Esling, P. (2014). [http://www.biolbull.org/content/227/2/93.long Next-generation environmental diversity surveys of foraminifera: preparing the future]. The Biological Bulletin, 227(2), 93-106.</ref><ref>{{cite web|title=World Foraminifera Database|url=http://www.marinespecies.org/foraminifera/}}</ref> They are usually less than 1&nbsp;mm in size, but some are much larger, the [[Xenophyophore|largest species]] reaching up to 20&nbsp;cm.<ref>{{cite news |author=Marshall M |title=Zoologger: 'Living beach ball' is giant single cell |newspaper=[[New Scientist]] |date=3 February 2010 |url=https://www.newscientist.com/article/dn18468}}</ref>

In modern scientific English, the term ''foraminifera'' is both singular and plural (irrespective of the word's [[Latin]] derivation), and is used to describe one or more specimens or taxa: its usage as singular or plural must be determined from context. Foraminifera is frequently used informally to describe the group, and in these cases is generally lowercase.<ref name=Lipps2011>{{cite journal|url=http://www.ucmp.berkeley.edu/people/klf/Lipps2011.pdf|access-date=10 April 2018 |title=What Should We call the Foraminifera |vauthors=Lipps JH, Finger KL, Walker SE |journal=Journal of Foraminiferal Research |volume=41 |issue=4 |pages=309–313 |date=October 2011|doi=10.2113/gsjfr.41.4.309 |bibcode=2011JForR..41..309L }}</ref>

== History of study ==
The earliest known reference to foraminifera comes from [[Herodotus]], who in the 5th century BCE noted them as making up the rock that forms the [[Great Pyramid of Giza]]. These are today recognized as representatives of the genus [[Nummulite|''Nummulites'']]. [[Strabo]], in the 1st Century BCE, noted the same foraminifera, and suggested that they were the remains of [[lentil]]s left by the workers who built the pyramids.<ref>{{Cite web|title=Foraminifera {{!}} Fossil Focus {{!}} Time {{!}} Discovering Geology {{!}} British Geological Survey (BGS)|url=https://www.bgs.ac.uk/discoveringGeology/time/Fossilfocus/foraminifera.html#folkloreAndFact|access-date=2020-07-20|website=bgs.ac.uk}}</ref>

[[Robert Hooke]] observed a foraminifera under the microscope, as described and illustrated in his 1665 book ''[[Micrographia]]:''<blockquote>I was trying several small and single Magnifying Glasses, and casually viewing a parcel of white Sand, when I perceiv'd one of the grains exactly shap'd and wreath'd like a Shell[...] I view'd it every way with a better Microscope and found it on both sides, and edge-ways, to resemble the Shell of a small Water-Snail with a flat spiral Shell[...]<ref>{{Cite web|title=Micrographia, or, Some physiological descriptions of minute bodies made by magnifying glasses ?with observations and inquiries thereupon /by R. Hooke ... : Hooke, Robert, : Free Download, Borrow, and Streaming|url=https://archive.org/details/mobot31753000817897|access-date=2020-07-20|website=Internet Archive|year=1665|language=en}}</ref></blockquote>[[Antonie van Leeuwenhoek]] described and illustrated foraminiferal tests in 1700, describing them as minute cockles; his illustration is recognizable as being ''[[Elphidium]]''.<ref name=SenGupta2003>{{Citation|last=Sen Gupta|first=Barun K.|date=2003|title=Modern Foraminifera|pages=7–36|editor-last=Sen Gupta|editor-first=Barun K.|chapter=Systematics of moder Foraminifera|publisher=Springer Netherlands|language=en|doi=10.1007/0-306-48104-9_2|isbn=978-0-306-48104-8}}</ref> Early workers classified foraminifera within the genus ''[[Nautilus]]'', noting their similarity to certain [[cephalopod]]s. It was recognised by [[Lorenz Spengler]] in 1781 that foraminifera had holes in the septa, which would eventually grant the group its name.<ref name=BOUDAGHERFADEL>{{Citation|last=BOUDAGHER-FADEL|first=MARCELLE K.|title=Biology and Evolutionary History of Larger Benthic Foraminifera|date=2018|work=Evolution and Geological Significance of Larger Benthic Foraminifera|pages=1–44|edition=2|publisher=UCL Press|doi=10.2307/j.ctvqhsq3.3 |jstor=j.ctvqhsq3.3|isbn=978-1-911576-94-5}}</ref> Spengler also noted that the septa of foraminifera arced the opposite way from those of nautili and that they lacked a nerve tube.<ref>{{Cite web|last=Hansen|first=H.|date=1981-01-01|title=On Lorentz Spengler and a neotype for the foraminifer Calcarina spengleri|url=https://www.researchgate.net/publication/242127606}}</ref>
[[File:Robert Hooke foraminifera.png|thumb|Earliest known illustration of a foraminifera shell, published by Robert Hooke in his 1665 book ''[[Micrographia]]'']]
[[Alcide d'Orbigny]], in his 1826 work, considered them to be a group of minute [[cephalopod]]s and noted their odd morphology, interpreting the pseudopodia as tentacles and noting the highly reduced (in actuality, absent) head.<ref>{{Cite journal|last=d'Orbigny|first=Alcide|date=1826|title=Tableau Méthodique de la Classe des Céphalopodes|url=https://www.biodiversitylibrary.org/item/28626#page/261/mode/1up|journal=Annales des Sciences Naturelles, Paris |series=Série 1|volume=7|pages=245–314|via=Biodiversity Heritage Library}}</ref> He named the group ''foraminifères'', or "hole-bearers", as members of the group had holes in the divisions between compartments in their shells, in contrast to [[Nautilus|nautili]] or [[ammonites]].<ref name=Lipps2011 />

The protozoan nature of foraminifera was first recognized by [[Félix Dujardin|Dujardin]] in 1835.<ref name=BOUDAGHERFADEL /> Shortly after, in 1852, d'Orbigny produced a classification scheme, recognising 72 genera of foraminifera, which he classified based on test shape—a scheme that drew severe criticism from colleagues.<ref name=SenGupta2003 />

[[Henry Bowman Brady|H.B. Brady]]'s 1884 monograph described the foraminiferal finds of the [[Challenger expedition|''Challenger'' expedition]]. Brady recognized 10 families with 29 subfamilies, with little regard to stratigraphic range; his taxonomy emphasized the idea that multiple different characters must separate taxonomic groups, and as such placed agglutinated and calcareous genera in close relation.

This overall scheme of classification would remain until [[Joseph Augustine Cushman|Cushman]]'s work in the late 1920s. Cushman viewed wall composition as the single most important trait in classification of foraminifera; his classification became widely accepted but also drew criticism from colleagues for being "not biologically sound".

Geologist [[Irene Crespin]] undertook extensive research in this field, publishing some ninety papers—including notable work on foraminifera—as sole author as well as more than twenty in collaboration with other scientists.<ref>{{Citation |title=Kennedy, Margaret Moore (1896–1967) |date=2018-02-06 |url=http://dx.doi.org/10.1093/odnb/9780192683120.013.34281 |work=Oxford Dictionary of National Biography |publisher=Oxford University Press |doi=10.1093/odnb/9780192683120.013.34281 |access-date=2022-11-03}}</ref>

Cushman's scheme nevertheless remained the dominant scheme of classification until Tappan and Loeblich's 1964 classification, which placed foraminifera into the general groupings still used today, based on microstructure of the test wall.<ref name="SenGupta2003" /> These groups have been variously moved around according to different schemes of higher-level classification. Pawlowski's (2013) use of molecular systematics has generally confirmed Tappan and Loeblich's groupings, with some being found as polyphyletic or paraphyletic; this work has also helped to identify higher-level relationships among major foraminiferal groups.<ref name="Pawlowski2013">{{Cite journal|last1=Pawlowski|first1=Jan|last2=Holzmann|first2=Maria|last3=Tyszka|first3=Jarosław|date=2013-04-01|title=New supraordinal classification of Foraminifera: Molecules meet morphology|url=http://www.sciencedirect.com/science/article/pii/S0377839813000327|journal=Marine Micropaleontology|language=en|volume=100|pages=1–10|doi=10.1016/j.marmicro.2013.04.002|bibcode=2013MarMP.100....1P|issn=0377-8398}}</ref>

==Taxonomy==

{{cladogram | caption= Phylogeny of Foraminifera following Pawlowski et al. 2013.<ref name=Pawlowski2013 /> The monothalamid orders [[Astrorhizida]] and [[Allogromiida]] are both paraphyletic. | clades =
{{clade
|1 = "Monothalamids" (paraphyletic)
|2 = {{clade
|1 = {{clade
|1 = [[Lagenida]]
|2 = {{clade
|1 = "Monothalamids"
|label2 = [[Tubothalamea]]
|2 = {{clade
|1 = [[Miliolida]]
|2 = [[Spirillinida]]
}}
}}
}}
|2 = {{clade
|1 = {{clade
|1 = "Monothalamids"
|2 = [[Xenophyophorea]]
}}
|label2 = [[Globothalamea]]
|2 = {{clade
|1 = "[[Textulariida]]" (paraphyletic)
|2 = [[Robertinida]]
|3 = [[Rotaliida]]
}}
}}
}}
}}
}}
The taxonomic position of the Foraminifera has varied since Schultze in 1854,<ref name="Treatise">{{cite book |last1=Loeblich |first1=A.R. Jr. |first2=H. |last2=Tappan |chapter=Foraminiferida |title=Part C, Protista 2 |publisher=Geological Society of America |year=1964 |isbn=978-0-8137-3003-5 |pages=C55–C786 |series=Treatise on Invertebrate Paleontology }}</ref>
who referred to as an order, Foraminiferida. [[Alfred R. Loeblich Jr|Loeblich]] (1987) and [[Helen Niña Tappan Loeblich|Tappan]] (1992) reranked Foraminifera as a class<ref name="Sen_Gupta02">{{cite book |first=Barun K. |last=Sen Gupta |title=Modern Foraminifera |url=https://books.google.com/books?id=K-3tUmXW-IgC&pg=PA16 |year=2002 |publisher=Springer |isbn=978-1-4020-0598-5 |page=16}}</ref> as it is now commonly regarded.

The Foraminifera have typically been included in the [[Protozoa]],<ref name = C-Smith04>{{cite journal |first=T |last=Cavalier-Smith |title=Only Six Kingdoms of Life |journal=Proceedings. Biological Sciences |year=2004 |volume=271 |issue=1545 |pages=1251–62 |doi=10.1098/rspb.2004.2705 |pmid=15306349 |pmc=1691724 |url=http://www.cladocera.de/protozoa/cavalier-smith_2004_prs.pdf}}</ref><ref name = C-Smith03>{{cite journal |first=T |last=Cavalier-Smith |title=Protist phylogeny and the high-level classification of Protozoa |journal=European Journal of Protistology |volume=34 |issue=4 |pages=338–348 |year=2003 |doi=10.1078/0932-4739-00002 }}</ref><ref>{{Cite web |url=http://tolweb.org/Cercozoa/121187 |title=Tolweb Cercozoa |access-date=21 June 2010 |archive-date=25 December 2019 |archive-url=https://web.archive.org/web/20191225170741/http://tolweb.org/Cercozoa/121187 |url-status=dead }}</ref> or in the similar Protoctista or [[Protist]] [[Kingdom (biology)|kingdom]].<ref>[http://www.marbef.org/data/aphia.php?p=browser European Register of Marine Species]</ref><ref>[http://www.eforams.icsr.agh.edu.pl/index.php/TAXONOMY eForams-taxonomy] {{webarchive|url=https://web.archive.org/web/20111003031806/http://www.eforams.icsr.agh.edu.pl/index.php/TAXONOMY |date=3 October 2011 }}</ref> Compelling evidence, based primarily on [[molecular phylogenetics]], exists for their belonging to a major group within the Protozoa known as the [[Rhizaria]].<ref name = C-Smith04/> Prior to the recognition of evolutionary relationships among the members of the Rhizaria, the Foraminifera were generally grouped with other [[Amoeba|amoeboid]]s as phylum Rhizopodea (or Sarcodina) in the class Granuloreticulosa.

The Rhizaria are problematic, as they are often called a "supergroup", rather than using an established [[taxonomic rank]] such as [[phylum]]. [[Thomas Cavalier-Smith|Cavalier-Smith]] defines the Rhizaria as an infra-kingdom within the kingdom Protozoa.<ref name = C-Smith04/>

Some taxonomies put the Foraminifera in a phylum of their own, putting them on par with the amoeboid Sarcodina in which they had been placed.

Although as yet unsupported by morphological correlates, molecular data strongly suggest the Foraminifera are closely related to the [[Cercozoa]] and [[Radiolaria]], both of which also include amoeboids with complex shells; these three groups make up the Rhizaria.<ref name = C-Smith03/> However, the exact relationships of the forams to the other groups and to one another are still not entirely clear. Foraminifera are closely related to [[testate amoebae]].<ref>{{citation|url=http://www6.plymouth.ac.uk/files/extranet/docs/ssb/quattestenv.pdf|title=Testate amoebae as environmental indicators|access-date=27 November 2016|archive-url=https://web.archive.org/web/20161127225520/http://www6.plymouth.ac.uk/files/extranet/docs/ssb/quattestenv.pdf|archive-date=27 November 2016|url-status=dead}}</ref>

{| class="wikitable collapsible collapsed" style="text-align: left; width:560px;"
|-
! Taxonomy from Mikhalevich 2013<ref>{{cite journal |last=Mikhalevich |first=V.I. | url=https://www.researchgate.net/publication/259562840 |title=New insight into the systematics and evolution of the foraminifera |journal=[[Micropaleontology]] |volume=59 |issue=6 |pages=493–527 |date=2013 |doi=10.47894/mpal.59.6.01 |bibcode=2013MiPal..59..493M |s2cid=90243148 }}</ref>
|-
|* '''Foraminifera''' <small>d'Orbigny 1826</small>
** Order [[Reticulomyxida]]
** '''Class Schizocladea''' <small>Cedhagen & Mattson 1992</small>
*** Order [[Schizocladida]]
** '''Class [[Xenophyophorea]]''' <small>Schultze 1904</small>
*** Order [[Stannomida]] <small>Tendal 1972</small>
*** Order [[Psamminida]] <small>Tendal 1972</small>
** '''Class [[Astrorhizata]]''' <small>Saidova 1981</small>
*** Subclass [[Lagynana]] <small>Mikhalevich 1980</small>
**** Order [[Ammoscalariida]] <small>Mikhalevich 1980</small>
**** Order [[Lagynida]] <small>Mikhalevich 1980</small>
**** Order [[Allogromiida]] <small>Loeblich & Tappan 1961</small>
*** Subclass [[Astrorhizana]] <small>Saidova 1981</small>
**** Order [[Astrorhizida]] <small>Lankester 1885</small>
**** Order [[Dendrophryida]] <small>Mikhalevich 1995</small>
**** Order [[Hippocrepinida]] <small>Saidova 1981</small>
**** Order †[[Parathuramminida]] <small>Mikhalevich 1980</small>
**** Order [[Psammosphaerida]] <small>Haeckel 1894</small>
** '''Class [[Rotaliata]]''' <small>Mikhalevich 1980</small> (hyaline foraminifers)
*** Subclass [[Globigerinana]] <small>Mikhalevich 1980</small>
**** Order [[Cassigerinellida]] <small>Mikhalevich 2013</small>
**** Order [[Globigerinida]] <small>Carpenter, Parker & Jones 1862</small>
**** Order [[Hantkeninida]] <small>Mikhalevich 1980</small>
**** Order [[Heterohelicida]] <small>Fursenko 1958</small>
**** Order [[Globorotaliida]] <small>Mikhalevich 1980</small>
*** Subclass [[Textulariana]] <small>Mikhalevich 1980</small>
**** Order [[Nautiloculinida]] <small>Mikhalevich 2003</small>
**** Order [[Spiroplectamminida]] <small>Mikhalevich 1992</small>
**** Order [[Textulariida]] <small>Delage & Hérouard 1896</small>
**** Order [[Trochamminida]] <small>Saidova 1981</small> ([[Carterinida]] <small>Loeblich & Tappan 1955</small>]
**** Order [[Verneuilinida]] <small>Mikhalevich & Kaminski 2003</small>
*** Subclass [[Rotaliana]] <small>Mikhalevich 1980</small>
**** Superorder [[Robertinoida]] <small>Mikhalevich 1980</small>
***** Order [[Robertinida]] <small>Mikhalevich 1980</small>
**** Superorder [[Nonionoida]] <small>Saidova 1981</small>
***** Order [[Elphidiida]] <small>Saidova 1981</small>
***** Order [[Nummulitida]] <small>Carpenter, Parker & Jones 1862</small>
***** Order †[[Orbitoidida]] <small>Copeland 1956</small>
***** Order [[Nonionida]] <small>Saidova 1981</small>
**** Superorder [[Buliminoida]] <small>Saidova 1981</small>
***** Order [[Cassidulinida]] <small>d'Orbigny 1839</small>
***** Order [[Buliminida]] <small>Saidova 1981</small>
***** Order [[Bolivinitida]] <small>Saidova 1981</small>
**** Superorder [[Discorboida]] <small>Ehrenberg 1838</small>
***** Order [[Chilostomellida]] <small>Haeckel 1894</small>
***** Order [[Discorbida]] <small>Ehrenberg 1838</small>
***** Order [[Glabratellida]] <small>Mikhalevich 1994</small>
***** Order [[Planorbulinida]] <small>Mikhalevich 1992</small>
***** Order [[Rotaliida]] <small>Lankester 1885</small>
***** Order [[Rosalinida]] <small>Delage & Hérouard 1896</small>
** '''Class [[Nodosariata]]''' <small>Mikhalevich 1992</small>
*** Subclass [[Hormosinana]] <small>Mikhalevich 1992</small>
**** Order [[Ammomarginulinida]] <small>Mikhalevich 2002</small>
**** Order [[Nouriida]] <small>Mikhalevich 1980</small>
**** Order †[[Pseudopalmulida]] <small>Mikhalevich 1992</small>
**** Order [[Saccamminida]] <small>Lankester 1885</small>
**** Order [[Hormosinida]] <small>Mikhalevich 1980</small>
*** Subclass [[Nodosariana]] <small>Mikhalevich 1992</small>
**** Order †[[Biseriamminida]] <small>Mikhalevich 1981</small>
**** Order [[Delosinida]] <small>Revets 1989</small>
**** Order [[Lagenida]] <small>Delage & Hérouard 1896</small>
**** Order †[[Palaeotextulariida]] <small>Hohenegger & Piller 1975</small>
**** Order [[Polymorphinida]] <small>Mikhalevich 1980</small>
**** Order [[Vaginulinida]] <small>Mikhalevich 1993</small>
**** Order [[Nodosariida]] <small>Calkins 1926</small>
** '''Class [[Spirillinata]]''' <small>Mikhalevich 1992</small>
*** Subclass [[Ammodiscana]] <small>Mikhalevich 1980</small>
**** Order †[[Plagioraphida]] <small>Mikhalevich 2003</small>
**** Order [[Ammodiscida]] <small>Mikhalevich 1980</small> [Pseudoammodiscoida <small>Conil & Lys 1970</small>]
**** Order [[Ammovertellinida]] <small>Mikhalevich 1999</small>
**** Order [[Ataxophragmiida]] <small>Fursenko 1958</small> [Orbitolinida <small>Ehrenberg 1839</small>]
*** Subclass [[Spirillinana]] <small>Mikhalevich 1992</small>
**** Superorder †[[Archaediscoida]] <small>Pojarkov & Skvortsov 1979</small>
***** Order †[[Archaediscida]] <small>Pojarkov & Skvortsov 1979</small>
***** Order †[[Lasiodiscida]] <small>Mikhalevich 1993</small>
***** Order †[[Tetrataxida]] <small>Mikhalevich 1981</small>
**** Superorder [[Involutinoida]] <small>Hohenegger & Piller 1977</small>
***** Order †[[Hottingerellida]] <small>Mikhalevich 1993</small>
***** Order [[Involutinida]] <small>Hohenegger & Piller 1977</small>
**** Superorder [[Spirillinoida]] <small>Hohenegger & Piller 1975 </small>
***** Order [[Seabrookiida]] <small>Mikhalevich 1980</small>
***** Order [[Cymbaloporida]] <small>Mikhaelevich 2013</small>
***** Order [[Spirillinida]] <small>Hohenegger & Piller 1975</small>
***** Order [[Patellinida]] <small>Mikhalevich 1992</small>
** '''Class [[Miliolata]]''' <small>Saidova 1981</small> (porcelaneous foraminifers)
*** Subclass [[Schlumbergerinana]] <small>Mikhalevich 1992</small>
**** Order [[Lituotubida]] <small>Mikhalevich 1992</small>
**** Order [[Loftusiida]] <small>Kaminski & Mikhalevich 2004</small>
**** Order [[Sphaeramminida]] <small>Mikhalevich & Kaminski 2004</small>
**** Order [[Cyclolinida]] <small>Mikhalevich 1992</small>
**** Order [[Haplophragmiida]] <small>Loeblich & Tappan 1989</small>
**** Order [[Schlumbergerinida]] <small>Mikhalevich 1980</small> [Rzehakinida <small>Saidova 1981</small>]
**** Order [[Lituolida]] <small>Lankester 1885</small>
**** Subclass [[Miliolana]] <small>Saidova 1981</small>
**** Clade Fusulinoids
***** Order †[[Ozawainellida]] <small>Solovieva 1980</small>
***** Order †[[Endothyroida]] <small>Fursenko 1958</small>
***** Order †[[Tournayellida]] <small>Hohenegger & Piller 1973</small>
***** Order †[[Fusulinida]] <small>Fursenko 1958</small>
***** Order †[[Neoschwagerinida]] <small>Minato & Honjo 1966</small>
***** Order †[[Schubertellida]] <small>Skinner 1931</small>
***** Order †[[Schwagerinida]] <small>Solovieva 1985</small>
***** Order †[[Staffellida]] <small>Miklukho-Maklay 1949</small>
**** Clade Milioloids
***** Order †[[Costiferida]] <small>Mikhalevich 1988</small>
***** Order [[Squamulinida]] <small>Mikhalevich 1988</small>
***** Order [[Cornuspirida]] <small>Jirovec 1953</small>
***** Order [[Soritida]] <small>Schultze 1854</small> [Orbitolitida <small>Wedekind 1937</small>]
***** Order [[Nubeculariida]] <small>Jones 1875</small>
***** Order [[Miliolida]] <small>Delage & Hérouard 1896</small>
|}

==Anatomy==
The most striking aspect of most foraminifera are their hard shells, or tests. These may consist of one of multiple chambers, and may be composed of protein, sediment particles, calcite, aragonite, or (in one case) silica.<ref name="Sen_Gupta02" /> Some foraminifera lack tests entirely.<ref name=":18">{{Cite journal|last1=Pawlowski|first1=Jan|last2=Bolivar|first2=Ignacio|last3=Fahrni|first3=Jose F.|last4=Vargas|first4=Colomban De|last5=Bowser|first5=Samuel S.|date=1999|title=Molecular Evidence That Reticulomyxa Filosa Is A Freshwater Naked Foraminifer|journal=Journal of Eukaryotic Microbiology|language=en|volume=46|issue=6|pages=612–617|doi=10.1111/j.1550-7408.1999.tb05137.x|pmid=10568034|s2cid=36497475|issn=1550-7408}}</ref> Unlike other shell-secreting organisms, such as [[Mollusca|molluscs]] or [[coral]]s, the tests of foraminifera are located inside the [[cell membrane]], within the [[protoplasm]]. The organelles of the cell are located within the {{Not a typo|compartment(s)}} of the test, and the {{Not a typo|hole(s)}} of the test allow the transfer of material from the pseudopodia to the internal cell and back.<ref name=Saraswati2016>{{Citation|last1=Saraswati|first1=Pratul Kumar|title=Calcareous-Walled Microfossils|date=2016|work=Micropaleontology: Principles and Applications|pages=81–119|editor-last=Saraswati|editor-first=Pratul Kumar|publisher=Springer International Publishing|language=en|doi=10.1007/978-3-319-14574-7_6|isbn=978-3-319-14574-7|last2=Srinivasan|first2=M. S.|editor2-last=Srinivasan|editor2-first=M.S.}}</ref>

The foraminiferal cell is divided into granular endoplasm and transparent ectoplasm from which a [[pseudopodia]]l net may emerge through a single opening or through many perforations in the test. Individual pseudopods characteristically have small granules streaming in both directions.<ref name="Sen_Gupta83">{{cite book|last=Sen Gupta|first=Barun K.|title=Foraminifera: notes for a short course organized by M.A. Buzas and B.K. Sen Gupta|publisher=University of Tennessee, Dept. of Geological Sciences|year=1982|isbn=978-0910249058|editor-last=Broadhead|editor-first=T.W.|series=Studies in Geology|volume=6|pages=37–50|chapter=Ecology of benthic Foraminifera|oclc=9276403|chapter-url=https://books.google.com/books?id=33hOAQAAIAAJ}}</ref> Foraminifera are unique in having ''granuloreticulose pseudopodia''; that is, their pseudopodia appear granular under the microscope; these pseudopodia are often elongate and may split and rejoin each other. These can be extended and retracted to suit the needs of the cell. The pseudopods are used for locomotion, anchoring, excretion, test construction and in capturing food, which consists of small organisms such as diatoms or bacteria.<ref name="Hemleben">{{cite book|last1=Hemleben|first1=C.|url=https://books.google.com/books?id=NaHOmAEACAAJ|title=Modern Planktonic Foraminifera|last2=Anderson|first2=O.R.|last3=Spindler|first3=M.|publisher=Springer-Verlag|year=1989|isbn=978-3-540-96815-3}}</ref><ref name=Saraswati2016 />

Aside from the tests, foraminiferal cells are supported by a [[cytoskeleton]] of microtubules, which are loosely arranged without the structure seen in other amoeboids. Forams have evolved special cellular mechanisms to quickly assemble and disassemble microtubules, allowing for the rapid formation and retraction of elongated pseudopodia.<ref name="Sen_Gupta02" />

[[File:2023 Foram.svg|thumb|center|upright=2|{{center|Detailed diagram of foraminifera morphology}}{{ordered list|Test|Proloculus (first chamber)|Chambers|Foramen (older apertures)|Endoplasm|Lipid globule|
[[Cell nucleus|Nucleus]]|
[[Nucleolus]]|
[[Endoplasmic reticulum]], the transport network for molecules going to specific parts of the cell|
Annular [[Lamella (cell biology)|lamellae]]|
[[Mitochondria|Mitochondrion]], creates [[Adenosine triphosphate|ATP]] (energy) for the cell|
Nascent annular lamellae|
[[Golgi apparatus]]; modifies [[protein]]s and sends them out of the cell|
[[Food vacuole|Digestive vacuole]]|
[[Peroxisome]], generates and scavenges hydrogen peroxide|
[[Phagosome|Phagocytic vacuole]]|
[[Lysosome]], holds enzymes|
Adhesive substance vesicle|
Aperture (opening of newest chamber)|
[[Ectoplasm (cell biology)|Ectoplasm]]|
Reticulopodia|
Adhesive granules|
Prey}}]]

In the gamont (sexual form), foraminifera generally have only a single nucleus, while the agamont (asexual form) tends to have multiple nuclei. In at least some species the nuclei are dimorphic, with the somatic nuclei containing three times as much protein and RNA than the generative nuclei. However, nuclear anatomy seems to be highly diverse.<ref>{{Cite journal|last=Grell|first=K. G.|date=1979-01-01|title=Cytogenetic systems and evolution in foraminifera|url=http://dx.doi.org/10.2113/gsjfr.9.1.1|journal=The Journal of Foraminiferal Research|volume=9|issue=1|pages=1–13|doi=10.2113/gsjfr.9.1.1|bibcode=1979JForR...9....1G |issn=0096-1191}}</ref> The nuclei are not necessarily confined to one chamber in multi-chambered species. Nuclei can be spherical or have many lobes. Nuclei are typically 30-50&nbsp;μm in diameter.<ref name=":19">{{Cite journal|date=2018-01-01|title=An overview of cellular ultrastructure in benthic foraminifera: New observations of rotalid species in the context of existing literature|journal=Marine Micropaleontology|language=en|volume=138|pages=12–32|doi=10.1016/j.marmicro.2017.10.005|issn=0377-8398|last1=Lekieffre|first1=Charlotte|last2=Bernhard|first2=Joan M.|last3=Mabilleau|first3=Guillaume|last4=Filipsson|first4=Helena L.|last5=Meibom|first5=Anders|last6=Geslin|first6=Emmanuelle|bibcode=2018MarMP.138...12L |doi-access=free|hdl=1912/9530|hdl-access=free}}</ref>

Some species of foraminifera have large, empty vacuoles within their cells; the exact purpose of these is unclear, but they have been suggested to function as a reservoir of nitrate.<ref name=":19" />

Mitochondria are distributed evenly throughout the cell, though in some species they are concentrated under the pores and around the external margin of the cell. This has been hypothesised to be an adaptation to low-oxygen environments.<ref name=":19" />

Several species of [[Xenophyophorea|xenophyophore]] have been found to have unusually high concentrations of [[Radionuclide|radioactive isotopes]] within their cells, among the highest of any eukaryote. The purpose of this is unknown.<ref>{{Cite journal|last=Domanov|first=M. M.|date=July 2015|title=Natural 226Ra and 232Th radionuclides in xenophyophores of the Pacific Ocean|url=http://link.springer.com/10.1134/S0016702915070034|journal=Geochemistry International|language=en|volume=53|issue=7|pages=664–669|doi=10.1134/S0016702915070034|bibcode=2015GeocI..53..664D |s2cid=127121951|issn=0016-7029}}</ref>

== Ecology ==
[[File:Living planktonic foraminifera.png|thumb|upright=2.5| {{center|'''Photomicrographs of living planktonic foraminifera''' <ref>Takagi, H., Kimoto, K., Fujiki, T., Saito, H., Schmidt, C., Kucera, M. and Moriya, K. (2019) "Characterizing photosymbiosis in modern planktonic foraminifera". ''Biogeosciences'', '''16'''(17). {{doi|10.5194/bg-16-3377-2019}}. [[File:CC-BY icon.svg|50px]] Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License].</ref>
}} (1) ''Orbulina universa'', (2) ''Sphaeroidinella dehiscens'', (3) ''Globigerinoides sacculifer'', (4) ''Globigerinoides conglobatus'', (5) ''Globigerinoides ruber'' (white), (6) ''Globigerinoides ruber'' (pink), (7) ''Globoturborotalita rubescens'', (8) ''Globoturborotalita tenella'', (9) ''Globigerinella calida'', (10) ''Globigerinella siphonifera'' Type I, (11) ''Globigerinella siphonifera'' Type II, (12) ''Globigerinella adamsi'', (13) ''Globigerina bulloides'', (14) ''Turborotalita quinqueloba'', (15) ''Turborotalita humilis'', (16) ''Hastigerina pelagica'', (17) ''Hastigerinella digitata'', (18) ''Neogloboquadrina incompta'', (19) ''Neogloboquadrina pachyderma'', (20) ''Neogloboquadrina dutertrei'', (21) ''[[Pulleniatina obliquiloculata]]'', (22) ''Globorotalia inflata'', (23) ''Globorotalia menardii'', (24) ''Globorotalia scitula'', (25) ''Globorotalia crassaformis'', (26) ''Globorotalia truncatulinoides'', (27) ''Candeina nitida'', (28) ''Globigerinita glutinata'', (29) ''Globigerinita uvula'', and (30) ''Tenuitella fleisheri''.
{{center|<small>Scale bars 200 μm</small>}}]]
Modern Foraminifera are primarily marine organisms, but living individuals have been found in brackish, freshwater<ref name="Sen_Gupta83" /> and even terrestrial habitats.<ref name="Lej" /> The majority of the species are [[benthos|benthic]], and a further 50 morphospecies are [[plankton]]ic.<ref name="Hemleben" /> This count may, however, represent only a fraction of actual diversity, since many genetically distinct species may be morphologically indistinguishable.<ref name="Kucera and Darling">{{cite journal|last1=Kucera|first1=M.|last2=Darling|first2=K.F.|date=April 2002|title=Cryptic species of planktonic foraminifera: their effect on palaeoceanographic reconstructions|journal=Philos Trans Royal Soc A|volume=360|issue=1793|pages=695–718|bibcode=2002RSPTA.360..695K|doi=10.1098/rsta.2001.0962|pmid=12804300|s2cid=21279683}}</ref>

Benthic foraminifera are typically found in fine-grained sediments, where they actively move between layers; however, many species are found on hard rock substrates, attached to seaweeds, or sitting atop the sediment surface.<ref name="Sen_Gupta02" />

The majority of planktonic foraminifera are found in the [[globigerinina]], a lineage within the [[rotaliida]].<ref name=Pawlowski2013 /> However, at least one other extant rotaliid lineage, ''[[Neogallitellia]]'', seems to have independently evolved a planktonic lifestyle.<ref name="Ujiié2008">{{Cite journal|last1=Ujiié|first1=Yurika|last2=Kimoto|first2=Katsunori|last3=Pawlowski|first3=Jan|date=December 2008|title=Molecular evidence for an independent origin of modern triserial planktonic foraminifera from benthic ancestors|journal=Marine Micropaleontology|language=en|volume=69|issue=3–4|pages=334–340|doi=10.1016/j.marmicro.2008.09.003|bibcode=2008MarMP..69..334U }}</ref><ref name="Özdikmen2009">{{Cite journal|last=Özdikmen|first=Hüseyin|date=June 2009|title=Substitute names for some unicellular animal taxa (Protozoa|url=https://www.munisentzool.org/yayin/vol4/issue2/MEZVol4No2.pdf|journal=Munis Entomology & Zoology|volume=4|issue=1|pages=233–256}}</ref> Further, it has been suggested that some Jurassic fossil foraminifera may have also independently evolved a planktonic lifestyle, and may be members of Robertinida.<ref name=Dubicka2019>{{Cite journal|last=Dubicka|first=Zofia|date=2019|title=Chamber arrangement versus wall structure in the high-rank phylogenetic classification of Foraminifera|journal=Acta Palaeontologica Polonica|volume=64|doi=10.4202/app.00564.2018|issn=0567-7920|doi-access=free}}</ref>

A number of forams, both benthic and planktonic,<ref>[https://microbiomejournal.biomedcentral.com/articles/10.1186/s40168-017-0257-7 Symbiosis and microbiome flexibility in calcifying benthic foraminifera of the Great Barrier Reef]</ref><ref>[https://bg.copernicus.org/articles/16/3377/2019/bg-16-3377-2019.pdf Characterizing photosymbiosis in modern planktonic foraminifera - BG]</ref> have unicellular [[algae]] as [[endosymbiont]]s, from diverse lineages such as the [[green algae]], [[red algae]], [[golden algae]], [[diatom]]s, and [[dinoflagellate]]s.<ref name="Hemleben" /> These [[mixotroph]]ic foraminifers are particularly common in nutrient-poor oceanic waters.<ref>[https://books.google.com/books?id=QvvlBwAAQBAJ&dq=%22The+symbiont-bearing+foraminifera+are+particularly+common+in+nutrient-poor+oceanic+waters%22&pg=PA22 Advances in Microbial Ecology, Volum 11]</ref> Some forams are [[kleptoplasty|kleptoplastic]], retaining [[chloroplast]]s from ingested algae to conduct [[photosynthesis]].<ref name="Bernhard and Bowser">{{Cite journal|last=Bernhard|first=J. M.|author2=Bowser, S.M.|year=1999|title=Benthic Foraminifera of dysoxic sediments: chloroplast sequestration and functional morphology|journal=Earth-Science Reviews|volume=46|issue=1|pages=149–165|bibcode=1999ESRv...46..149B|doi=10.1016/S0012-8252(99)00017-3}}</ref>

Most foraminifera are heterotrophic, consuming smaller organisms and organic matter; some smaller species are specialised feeders on [[phytodetritus]], while others specialise in consuming diatoms. Some benthic forams construct feeding cysts, using the pseuodopodia to encyst themselves inside of sediment and organic particles.<ref name="Sen_Gupta02" /> Certain foraminifera prey upon small animals such as [[copepod]]s or [[cumacea]]ns; some forams even predate upon other forams, drilling holes into the tests of their prey.<ref name="Goldstein 2003 37–55">{{Citation|last=Goldstein|first=Susan T.|date=2003|title=Modern Foraminifera|pages=37–55|editor-last=Sen Gupta|editor-first=Barun K.|chapter=Foraminifera: A biological overview|publisher=Springer Netherlands|language=en|doi=10.1007/0-306-48104-9_3|isbn=978-0-306-48104-8}}</ref> One group, the xenophyophores, has been suggested to farm bacteria within their tests, although studies have failed to find support for this hypothesis.<ref>{{Cite journal|last1=Tsuchiya|first1=Masashi|last2=Nomaki|first2=Hidetaka|date=2021-10-01|title=Rapid response of the giant protist xenophyophores (Foraminifera, Rhizaria) to organic matter supply at abyssal depths revealed by an in situ dual stable isotope labeling experiment|url=https://www.sciencedirect.com/science/article/pii/S0967063721001473|journal=Deep Sea Research Part I: Oceanographic Research Papers|language=en|volume=176|pages=103608|doi=10.1016/j.dsr.2021.103608|bibcode=2021DSRI..17603608T |issn=0967-0637}}</ref> [[Suspension feeding]] is also common in the group, and at least some species can take advantage of [[dissolved organic carbon]].<ref name="Sen_Gupta02" />

A few foram species are [[Parasitism|parasitic]], infecting sponges, molluscs, corals, or even other foraminifera. Parasitic strategies vary; some act as ectoparasites, using their pseudopodia to steal food from the host, while others burrow through the shell or body wall of their host to feed on its soft tissue.<ref name="Sen_Gupta02" />

Foraminifera are themselves eaten by a host of larger organisms, including invertebrates, fish, shorebirds, and other foraminifera. It has been suggested, however, that in some cases predators may be more interested in the calcium from foram shells than in the organisms themselves. Several aquatic snail species are known to selectively feed upon foraminifera, often even preferring individual species.<ref>{{Citation|last1=Culver|first1=Stephen J.|title=Predation on and by Foraminifera|date=2003|url=http://link.springer.com/10.1007/978-1-4615-0161-9_2|work=Predator—Prey Interactions in the Fossil Record|pages=7–32|editor-last=Kelley|editor-first=Patricia H.|place=Boston, MA|publisher=Springer US|doi=10.1007/978-1-4615-0161-9_2|isbn=978-1-4613-4947-1|access-date=2020-09-30|last2=Lipps|first2=Jere H.|editor2-last=Kowalewski|editor2-first=Michał|editor3-last=Hansen|editor3-first=Thor A.}}</ref>

Certain benthic foraminifera have been found to be capable of surviving [[Anoxic waters|anoxic]] conditions for over 24 hours, indicating that they are capable of selective [[anaerobic respiration]]. This is interpreted as an adaptation to survive changing oxygenic conditions near the sediment-water interface.<ref>{{Cite journal|last1=Moodley|first1=L.|last2=Hess|first2=C.|date=1992-08-01|title=Tolerance of Infaunal Benthic Foraminifera for Low and High Oxygen Concentrations|journal=The Biological Bulletin|volume=183|issue=1|pages=94–98|doi=10.2307/1542410|issn=0006-3185|jstor=1542410|pmid=29304574|url=https://www.biodiversitylibrary.org/part/22909}}</ref>

Foraminifera are found in the deepest parts of the ocean such as the [[Mariana Trench]], including the [[Challenger Deep]], the deepest part known.  At these depths, below the [[carbonate compensation depth]], the calcium carbonate of the tests is soluble in water due to the extreme pressure. The Foraminifera found in the Challenger Deep thus have no carbonate test, but instead have one of organic material.<ref name="organicWalled">{{cite journal|last1=Gooday|first1=A.J.|last2=Todo|first2=Y.|last3=Uematsu|first3=K.|last4=Kitazato|first4=H.|date=July 2008|title=New organic-walled Foraminifera (Protista) from the ocean's deepest point, the Challenger Deep (western Pacific Ocean)|journal=Zoological Journal of the Linnean Society|volume=153|issue=3|pages=399–423|doi=10.1111/j.1096-3642.2008.00393.x|url=https://zenodo.org/record/5447678 |doi-access=free}}</ref>

Nonmarine foraminifera have traditionally been neglected in foram research, but recent studies show them to be substantially more diverse than previously known. They are known to inhabit disparate ecological niches, including [[moss]]es, rivers, lakes and ponds, wetlands, soils, [[Bog|peat bogs]], and sand dunes.<ref>{{Cite journal|last1=Holzmann|first1=Maria|last2=Gooday|first2=Andrew J.|last3=Siemensma|first3=Ferry|last4=Pawlowski|first4=Jan|date=2021-10-29|title=Review: Freshwater and Soil Foraminifera – A Story of Long-Forgotten Relatives|url=https://doi.org/10.2113/gsjfr.51.4.318|journal=Journal of Foraminiferal Research|volume=51|issue=4|pages=318–331|doi=10.2113/gsjfr.51.4.318|bibcode=2021JForR..51..318H |s2cid=240240437 |issn=0096-1191}}</ref>

== Reproduction ==
The generalized foraminiferal life-cycle involves an alternation between [[Ploidy#Haploid and monoploid|haploid]] and [[Ploidy|diploid]] generations, although they are mostly similar in form.<ref name="Treatise" /><ref name="M,L &F">{{cite book|last1=Moore|first1=R.C.|title=Invertebrate Fossils|last2=Lalicker|first2=A.G.|last3=Fischer|first3=C.G.|publisher=McGraw-Hill|year=1952|chapter=Ch 2 Foraminifera and Radiolaria|oclc=547380}}</ref> The haploid or gamont initially has a single [[cell nucleus|nucleus]], and divides to produce numerous [[gamete]]s, which typically have two [[flagellum|flagella]].  The diploid or agamont is [[multinucleate]], and after [[meiosis]] divides to produce new gamonts.  Multiple rounds of [[asexual reproduction]] between sexual generations are not uncommon in benthic forms.<ref name="Sen_Gupta83" />
[[File:Foraminifera life cycle.png|thumb|379x379px|Diagram of a typical foraminiferan life cycle, showing characteristic alternation of generations.]]
Foraminifera exhibit morphological dimorphism associated with their reproductive cycle. The gamont, or sexually reproducing haploid form, is ''megalospheric''—that is, its ''proloculus'', or first chamber, is proportionally large. The gamont is also known as the ''A'' form. Gamonts, despite having typically larger proloculi, also generally have smaller overall test diameter than do agamonts.

After reaching maturity, the gamont divides via [[mitosis]] to produce thousands of gametes which are also haploid. These gametes all have a full set of [[organelle]]s, and are expelled from the test into the environment leaving the test undamaged. Gametes are not differentiated into [[sperm]] and [[Egg cell|egg]], and any two gametes from a species can generally fertilize each other.
[[File:Megalosphere and Microsphere.png|left|thumb|Morphs present in the foram life cycle—the megalosphere and the microsphere. The name derives from the size of the proloculus, or first chamber, and as such the microsphere has a larger overall size.]]
When two gametes combine, they create a diploid, multi-nucleated cell known as the ''agamont,'' or ''B'' form. In contrast to the gamont, the agamont is ''microspheric'', with a proportionally small first chamber but typically larger overall diameter with more chambers. The agamont is the [[asexual reproduction]] phase of the foraminifera; upon reaching adulthood, the protoplasm entirely vacates the test and divides its [[cytoplasm]] [[Meiosis|meiotically]] via [[multiple fission]] to form a number of haploid offspring. These offspring then begin to form their megalospheric first chamber before dispersing.

In some cases the haploid young may mature into a megalospheric form which then reproduces asexually to produce another megalospheric, haploid offspring. In this case, the first megalospheric form is referred to as the ''schizont'' or ''A<sub>1</sub>'' form, while the second is referred to as the gamont or ''A<sub>2</sub>'' form.

[[File:Nummulitids.jpg|thumb|Fossil [[Nummulite|nummulitid]] foraminiferans showing microspheric (larger) and megalospheric individuals (smaller); [[Eocene]] of the United Arab Emirates; scale in mm|alt=]]

Maturation and reproduction occur more slowly in cooler and deeper water; these conditions also cause forams to grow larger. ''A'' forms always seem to be much more numerous than are ''B'' forms, likely due to the reduced likelihood of two gametes encountering one another and successfully combining.<ref name=Haynes1981 /><ref name=Saraswati2016 />

=== Variations in reproductive mode ===
There is a high degree of diversity in reproductive strategies in different foraminiferal groups.

In [[Monothalamea|unilocular species]], the ''A'' form and ''B'' form are still present. As in the microspheric morph of multilocular forams, the asexually reproducing ''B'' form is larger than the sexually reproducing ''A'' form.

Forams in the family [[Spirillinidae]] have amoeboid gametes rather than flagellated. Other aspects of reproduction in this group are generally similar to that of other groups of forams.

The calcareous [[Spirillinida|spirillinid]] ''[[Patellina|Patellina corrugata]]'' has a slightly different reproductive strategy than most other foraminifera. The asexually reproducing ''B'' form produces a cyst that surrounds the entire cell; it then divides within this cyst and the juvenile cells cannibalise the calcite of the parent's test to form the first chamber of their own test. These ''A'' forms, upon maturity, gather into groups of up to nine individuals; they then form a protective cyst around the whole group. [[Gametogenesis]] occurs within this cyst, producing very low numbers of gametes.  The ''B'' form larvae are produced inside of the cyst; any nuclei that are not bound into cells are consumed as food for the developing larvae. ''Patellina'' in ''A'' form is reportedly [[dioecious]], with sexes referred to as the "plus" and "minus"; these sexes differ in number of nuclei, with the "plus" form having three nuclei and the "minus" form having four nuclei. The ''B'' form is again larger than the ''A'' form.<ref name=Saraswati2016 /><ref name=Haynes1981>{{Cite book|last=Haynes|first=J. R.|url=https://books.google.com/books?id=y5ewCwAAQBAJ&q=foraminifera+john+r+haynes&pg=PP7|title=Foraminifera|date=1981-06-18|publisher=Springer|isbn=978-1-349-05397-1|language=en}}</ref><ref name="Goldstein 2003 37–55" />

==Tests==
{{main|Foraminifera test}}
{{see also|Protist shell}}
[[File:benthic foraminifera.jpg|thumb|upright=1.2| {{center|Foraminiferan tests (ventral view)}}]]
{{biomineralization sidebar|exoskeletons}}

Foraminiferal [[Test (biology)|tests]] serve to protect the organism within. Owing to their generally hard and durable construction (compared to other protists), the tests of foraminifera are a major source of scientific knowledge about the group.

Openings in the test that allow the cytoplasm to extend outside are called apertures.<ref name="Lana2001">{{Cite journal|last1=Lana|first1=C|year=2001|title=Cretaceous Carterina (Foraminifera)|journal=Marine Micropaleontology|volume=41|issue=1–2|pages=97–102|bibcode=2001MarMP..41...97L|doi=10.1016/S0377-8398(00)00050-5}}</ref> The ''primary'' aperture, leading to the exterior, take many different shapes in different species, including but not limited to rounded, crescent-shaped, slit-shaped, hooded, radiate (star-shaped), dendritic (branching). Some foraminifera have "toothed", flanged, or lipped primary apertures. There may be only one primary aperture or multiple; when multiple are present, they may be clustered or equatorial. In addition to the primary aperture, many foraminifera have ''supplemental'' apertures. These may form as relict apertures (past primary apertures from an earlier growth stage) or as unique structures.

Test shape is highly variable among different foraminifera; they may be single-chambered (unilocular) or multi-chambered (multilocular). In multilocular forms, new chambers are added as the organism grows. A wide variety of test morphologies is found in both unilocular and multilocular forms, including spiraled, serial, and milioline, among others.<ref name=Saraswati2016 />

Many foraminifera exhibit dimorphism in their tests, with megalospheric and microspheric individuals. These names should not be taken as referring to the size of the full organism; rather, they refer to the size of the first chamber, or ''proloculus''. Tests as fossils are known from as far back as the [[Ediacaran]] period,<ref name=Kontorovich2008>{{Cite journal|last1=Kontorovich|first1=A. E.|last2=Varlamov|first2=A. I.|last3=Grazhdankin|first3=D. V.|last4=Karlova|first4=G. A.|last5=Klets|first5=A. G.|last6=Kontorovich|first6=V. A.|last7=Saraev|first7=S. V.|last8=Terleev|first8=A. A.|last9=Belyaev|first9=S. Yu.|last10=Varaksina|first10=I. V.|last11=Efimov|first11=A. S.|date=2008-12-01|title=A section of Vendian in the east of West Siberian Plate (based on data from the Borehole Vostok 3)|url=http://www.sciencedirect.com/science/article/pii/S106879710800206X|journal=Russian Geology and Geophysics|language=en|volume=49|issue=12|pages=932–939|doi=10.1016/j.rgg.2008.06.012|bibcode=2008RuGG...49..932K|issn=1068-7971}}</ref> and many marine sediments are composed primarily of them.  For instance, the limestone that makes up the pyramids of Egypt is composed almost entirely of [[Nummulite|nummulitic]] benthic Foraminifera.<ref>[http://www.ucl.ac.uk/GeolSci/micropal/foram.html#histofstudy Foraminifera: History of Study], [[University College London]], retrieved 20 September 2007</ref> It is estimated that reef Foraminifera generate about 43 million tons of calcium carbonate per year.<ref name="Langer. et al. 1997">{{Cite journal|title = Global ocean carbonate and carbon dioxide production: The role of reef Foraminifera |year = 1997|last= Langer|first=M. R.|author2=Silk, M. T. B. |author3=Lipps, J. H. |journal = Journal of Foraminiferal Research|volume = 27|issue = 4|pages = 271–277|doi = 10.2113/gsjfr.27.4.271| bibcode=1997JForR..27..271L |url=http://jfr.geoscienceworld.org/cgi/content/abstract/27/4/271}}</ref>

Genetic studies have identified the naked amoeba ''[[Reticulomyxa]]'' and the peculiar [[xenophyophore]]s as foraminiferans without tests. A few other amoeboids produce reticulose pseudopods, and were formerly classified with the forams as the Granuloreticulosa, but this is no longer considered a natural group, and most are now placed among the Cercozoa.<ref name="Adl. et al.">{{Cite journal|title = The new higher level classification of Eukaryotes with emphasis on the taxonomy of Protists|year = 2005|last= Adl|first=S. M.|author2=Simpson, A. G. B. |author3=Farmer, M. A. |author4=Anderson  |journal = Journal of Eukaryotic Microbiology|volume = 52|issue = 5|pages = 399–451|doi = 10.1111/j.1550-7408.2005.00053.x|pmid = 16248873|s2cid = 8060916|display-authors=etal|doi-access = free}}</ref>

== Evolutionary history ==
Molecular clocks indicate that the crown-group of foraminifera likely evolved during the [[Neoproterozoic]], between 900 and 650 million years ago; this timing is consistent with Neoproterozoic fossils of the closely related [[Filosa|filose amoebae]]. As fossils of foraminifera have not been found prior to the very end of the [[Ediacaran]], it is likely that most of these Proterozoic forms did not have hard-shelled tests.<ref name=Pawlowski2003>{{Cite journal|last1=Pawlowski|first1=Jan|last2=Holzmann|first2=Maria|last3=Berney|first3=Cédric|last4=Fahrni|first4=José|last5=Gooday|first5=Andrew J.|last6=Cedhagen|first6=Tomas|last7=Habura|first7=Andrea|last8=Bowser|first8=Samuel S.|date=2003-09-30|title=The evolution of early Foraminifera|journal=Proceedings of the National Academy of Sciences|language=en|volume=100|issue=20|pages=11494–11498|doi=10.1073/pnas.2035132100|issn=0027-8424|pmid=14504394|pmc=208786|bibcode=2003PNAS..10011494P|doi-access=free}}</ref><ref>{{Cite journal|last1=Groussin|first1=Mathieu|last2=Pawlowski|first2=Jan|last3=Yang|first3=Ziheng|date=2011-10-01|title=Bayesian relaxed clock estimation of divergence times in foraminifera|url=http://www.sciencedirect.com/science/article/pii/S1055790311002752|journal=Molecular Phylogenetics and Evolution|language=en|volume=61|issue=1|pages=157–166|doi=10.1016/j.ympev.2011.06.008|pmid=21723398|bibcode=2011MolPE..61..157G |issn=1055-7903}}</ref>

Due to their non-mineralised tests, "[[Allogromiida|allogromiids]]" have no fossil record.<ref name=Pawlowski2003 />
[[File:Paleodictyon P.San García Algeciras I03.JPG|left|thumb|The mysterious ''[[Paleodictyon]]'' has been interpreted as a fossil [[Xenophyophorea|xenophyophore]] but this remains controversial.]]
The mysterious [[vendozoa]]ns of the Ediacaran period have been suggested to represent fossil [[Xenophyophorea|xenophyophores]].<ref>{{Cite journal|last=Seilacher|first=A.|s2cid=128619251|date=2007-01-01|title=The nature of vendobionts|url=https://sp.lyellcollection.org/content/286/1/387|journal=Geological Society, London, Special Publications|language=en|volume=286|issue=1|pages=387–397|doi=10.1144/SP286.28|bibcode=2007GSLSP.286..387S|issn=0305-8719}}</ref> However, the discovery of [[Diagenesis|diagenetically altered]] C<sub>27</sub> [[sterol]]s associated with the remains of ''[[Dickinsonia]]'' cast doubt on this identification and suggest it may instead be an animal.<ref>{{Cite journal|last1=Bobrovskiy|first1=Ilya|last2=Hope|first2=Janet M.|last3=Ivantsov|first3=Andrey|last4=Nettersheim|first4=Benjamin J.|last5=Hallmann|first5=Christian|last6=Brocks|first6=Jochen J.|date=2018-09-21|title=Ancient steroids establish the Ediacaran fossil Dickinsonia as one of the earliest animals|journal=Science|language=en|volume=361|issue=6408|pages=1246–1249|doi=10.1126/science.aat7228|issn=0036-8075|pmid=30237355|bibcode=2018Sci...361.1246B|doi-access=free|hdl=1885/230014|hdl-access=free}}</ref> Other researchers have suggested that the elusive trace fossil ''[[Paleodictyon]]'' and its [[Graphoglyptidae|relatives]] may represent a fossil xenophyophore<ref>{{Cite journal|last=Swinbanks|first=D. D.|s2cid=28690086|date=1982-10-01|title=Piaeodicton: The Traces of Infaunal Xenophyophores?|url=https://www.science.org/doi/10.1126/science.218.4567.47|journal=Science|language=en|volume=218|issue=4567|pages=47–49|doi=10.1126/science.218.4567.47|issn=0036-8075|pmid=17776707|bibcode=1982Sci...218...47S}}</ref> and noted the similarity of the extant xenophyophore ''[[Occultammina]]'' to the fossil;<ref name=Levin1994>{{Cite journal|last=Levin|first=Lisa A.|date=1994|title=Paleoecology and Ecology of Xenophyophores|journal=PALAIOS|volume=9|issue=1|pages=32–41|doi=10.2307/3515076|jstor=3515076|bibcode=1994Palai...9...32L|issn=0883-1351}}</ref> however, modern examples of ''Paleodictyon'' have not been able to clear up the issue and the trace may alternately represent a burrow or a [[Hexactinellid|glass sponge.]]<ref>{{Cite journal|last1=Rona|first1=Peter A.|last2=Seilacher|first2=Adolf|last3=de Vargas|first3=Colomban|last4=Gooday|first4=Andrew J.|last5=Bernhard|first5=Joan M.|last6=Bowser|first6=Sam|last7=Vetriani|first7=Costantino|last8=Wirsen|first8=Carl O.|last9=Mullineaux|first9=Lauren|last10=Sherrell|first10=Robert|last11=Frederick Grassle|first11=J.|date=2009-09-01|title=Paleodictyon nodosum: A living fossil on the deep-sea floor|url=http://www.sciencedirect.com/science/article/pii/S0967064509001799|journal=Deep Sea Research Part II: Topical Studies in Oceanography|series=Marine Benthic Ecology and Biodiversity: A Compilation of Recent Advances in Honor of J. Frederick Grassle|language=en|volume=56|issue=19|pages=1700–1712|doi=10.1016/j.dsr2.2009.05.015|bibcode=2009DSRII..56.1700R|issn=0967-0645}}</ref> Supporting this notion is the similar habitat of living xenophyophores to the inferred habitat of fossil graphoglyptids; however, the large size and regularity of many graphoglyptids as well as the apparent absence of xenophyae in their fossils casts doubt on the possibility.<ref name=Levin1994 /> As of 2017 no definite xenophyophore fossils have been found.<ref>{{Cite journal|last1=Gooday|first1=Andrew J|last2=Holzmann|first2=Maria|last3=Caulle|first3=Clémence|last4=Goineau|first4=Aurélie|last5=Kamenskaya|first5=Olga|last6=Weber|first6=Alexandra A. -T.|last7=Pawlowski|first7=Jan|date=2017-03-01|title=Giant protists (xenophyophores, Foraminifera) are exceptionally diverse in parts of the abyssal eastern Pacific licensed for polymetallic nodule exploration|journal=Biological Conservation|language=en|volume=207|pages=106–116|doi=10.1016/j.biocon.2017.01.006|issn=0006-3207|doi-access=free|bibcode=2017BCons.207..106G }}</ref>

Test-bearing foraminifera have an excellent fossil record throughout the [[Phanerozoic]] eon. The earliest known definite foraminifera appear in the fossil record towards the very end of the Ediacaran; these forms all have agglutinated tests and are unilocular. These include forms like ''[[Platysolenites]]'' and ''[[Spirosolenites]]''.<ref>{{Cite journal|last1=McIlroy|first1=Duncan|last2=Green|first2=O. R.|last3=Brasier|first3=M. D.|date=2001|title=Palaeobiology and evolution of the earliest agglutinated Foraminifera: Platysolenites, Spirosolenites and related forms|journal=Lethaia|language=en|volume=34|issue=1|pages=13–29|doi=10.1080/002411601300068170|bibcode=2001Letha..34...13M |issn=1502-3931}}</ref><ref name=Kontorovich2008 />
Single-chambered foraminifera continued to diversify throughout the Cambrian. Some commonly encountered forms include ''[[Ammodiscus]], [[Glomospira]],''  ''[[Psammosphera]],'' and ''[[Turritellella]]''; these species are all agglutinated. They make up part of the [[Ammodiscacea|Ammodiscina]], a lineage of [[Spirillinida|spirillinids]] that still contains modern forms.<ref name=Scott2003>{{Cite journal|last1=Scott|first1=David B.|last2=Medioli|first2=Franco|last3=Braund|first3=Regan|date=2003-06-01|title=Foraminifera from the Cambrian of Nova Scotia: The oldest multichambered foraminifera|url=https://pubs.geoscienceworld.org/micropal/article-abstract/49/2/109/125201/Foraminifera-from-the-Cambrian-of-Nova-Scotia-The|journal=Micropaleontology|language=en|volume=49|issue=2|pages=109–126|doi=10.2113/49.2.109|issn=1937-2795}}</ref><ref name=Pawlowski2013 /> Later spirillinids would evolve multilocularity and calcitic tests, with the first such forms appearing during the [[Triassic]]; the group saw little effects on diversity due to the [[K-Pg Extinction|K-Pg extinction]].<ref name=Tappan1988>{{Cite journal|last1=Tappan|first1=Helen|last2=Loeblich|first2=Alfred R.|date=1988|title=Foraminiferal Evolution, Diversification, and Extinction|journal=Journal of Paleontology|volume=62|issue=5|pages=695–714|jstor=1305391|issn=0022-3360}}</ref>

The earliest multi-chambered foraminifera are agglutinated species, and appear in the fossil record during the middle [[Cambrian]] period. Due to their poor preservation they cannot be positively assigned to any major foram group.<ref name=Scott2003 />
[[File:Fusulinid cutaway.gif|thumb|Cutaway view of a [[Fusulinida|Fusulinid]]|246x246px]]
The earliest known calcareous-walled foraminifera are the [[Fusulinida|Fusulinids]], which appear in the fossil record during the [[Llandovery epoch|Llandoverian]] epoch of the early [[Silurian]]. The earliest of these were microscopic, planispirally coiled, and evolute; later forms evolved a diversity of shapes including lenticular, globular, and elongated rice-shaped forms.<ref>{{cite book |last1=Wagner |first1=Robert Herman |title=The Carboniferous of the World: China, Korea, Japan & S.E. Asia |date=1983 |publisher=IGME |isbn=978-84-300-9949-8 |page=88 |url=https://books.google.com/books?id=NNTkn2pI4MUC |language=en}}</ref><ref>{{cite book |last1=Goldberg |first1=Walter M. |title=The Biology of Reefs and Reef Organisms |date=4 October 2013 |publisher=University of Chicago Press |isbn=978-0-226-92537-0 |page=73 |url=https://books.google.com/books?id=pfmsAAAAQBAJ&pg=PA73 |access-date=10 January 2023 |language=en}}</ref>

Later species of fusulinids grew to much larger size, with some forms reaching 5&nbsp;cm in length; reportedly, some specimens reach up to 14&nbsp;cm in length, making them among the largest foraminifera extant or extinct. Fusulinids are the earliest lineage of foraminifera thought to have evolved symbiosis with photosynthetic organisms. Fossils of fusulinids have been found on all continents except [[Antarctica]]; they reached their greatest diversity during the [[Viséan|Visean]] epoch of the [[Carboniferous]]. The group then gradually declined in diversity until finally going extinct during the [[Permian–Triassic extinction event|Permo-Triassic extinction event]].<ref name=Saraswati2016 /><ref name=Tappan1988 /><ref>{{Cite web|title=Fusulinids {{!}} GeoKansas|url=http://geokansas.ku.edu/fusulinids|website=geokansas.ku.edu|access-date=2020-05-16}}</ref>

During the [[Tournaisian]] epoch of the Carboniferous, [[Miliolida|Miliolid]] foraminifera first appeared in the fossil record, having diverged from the [[Spirillinida|spirillinids]] within the [[Tubothalamea]]. Miliolids suffered about 50% casualties during both the Permo-Triassic and K-Pg extinctions but survived to the present day. Some fossil miliolids reached up to 2&nbsp;cm in diameter.<ref name=Tappan1988 />
[[File:Foraminifera hg.jpg|left|thumb|A fossil test from a planktonic [[globigerinina]]n foraminifera.]]
The earliest known [[Lagenida|Lagenid]] fossils appear during the [[Moscovian (Carboniferous)|Moscovian]] epoch of the Carboniferous. Seeing little effect due to the Permo-Triassic or K-Pg extinctions, the group diversified through time. Secondarily unilocular taxa evolved during the Jurassic and Cretaceous.

The earliest [[Involutinida|Involutinid]] fossils appear during the Permian; the lineage diversified throughout the Mesozoic of Eurasia before apparently vanishing from the fossil record following the [[Cenomanian-Turonian boundary event|Cenomanian-Turonian Ocean Anoxic Event]]. The extant group [[planispirillinidae]] has been referred to the involutinida, but this remains the subject of debate.<ref>{{Cite web|title=PBDB Navigator|url=https://paleobiodb.org/navigator/#/b191337c|last=Czaplewski|first=John J.|website=paleobiodb.org|access-date=2020-05-16}}</ref><ref name=Tappan1988 />

The [[Robertinida]] first appear in the fossil record during the [[Anisian]] epoch of the Triassic. The group remained at low diversity throughout its fossil history; all living representatives belong to the [[Robertinidae]], which first appeared during the [[Paleocene]].<ref name=Tappan1988 />

The first definite [[Rotaliida|Rotaliid]] fossils do not appear in the fossil record until the [[Pliensbachian]] epoch of the Jurassic, following the [[Triassic–Jurassic extinction event|Triassic-Jurassic event]].<ref>{{Cite journal|last=Gräfe|first=K.U.|s2cid=55664447|date=2005|title=Benthic foraminifers and palaeoenvironment in the Lower and Middle Jurassic of the Western Basque-Cantabrian Basin (Northern Spain)|journal=Journal of Iberian Geology|volume=31|issue=2|pages=217–233}}</ref> Diversity of the group remained low until the aftermath of the Cenomanian-Turonian event, after which the group saw a rapid diversification. Of this group, the planktonic [[Globigerinina]]—the first known group of planktonic forams—first appears in the aftermath of the [[Toarcian turnover|Toarcian Turnover]]; the group saw heavy losses during both the K-Pg extinction and the [[Eocene–Oligocene extinction event|Eocene-Oligocene extinction]], but remains extant and diverse to this day.<ref name=Tappan1988 /> An additional evolution of planktonic lifestyle occurred in the Miocene or Pliocene, when the rotaliid ''[[Neogallitellia]]'' independently evolved a planktonic lifestyle.<ref name="Ujiié2008" /><ref name="Özdikmen2009" />

==Paleontological applications==
Dying planktonic Foraminifera continuously rain down on the sea floor in vast numbers, their mineralized tests preserved as fossils in the accumulating [[Pelagic sediments|sediment]]. Beginning in the 1960s, and largely under the auspices of the [[Deep Sea Drilling Program|Deep Sea Drilling]], [[Ocean Drilling Program|Ocean Drilling]], and International Ocean Drilling Programmes, as well as for the purposes of oil exploration, advanced deep-sea drilling techniques have been bringing up sediment cores bearing Foraminifera fossils.<ref name="Nature">{{Cite journal | url=http://www.nature.com/nature/debates/fossil/fossil_1.html | title=Nature debates| journal=Nature| date=19 November 1998| pages=1–3| doi=10.1038/nature28135| last1=Pearson| first1=Paul| doi-access=free}}</ref> The effectively unlimited supply of these fossil tests and the relatively high-precision age-control models available for cores has produced an exceptionally high-quality planktonic Foraminifera fossil record dating back to the mid-[[Jurassic]], and presents an unparalleled record for scientists testing and documenting the evolutionary process.<ref name="Nature" /> The exceptional quality of the fossil record has allowed an impressively detailed picture of species inter-relationships to be developed on the basis of fossils, in many cases subsequently validated independently through molecular genetic studies on extant specimens<ref>Journal bioinformatics and biology insights, [http://www.la-press.com/using-the-multiple-analysis-approach-to-reconstruct-phylogenetic-relat-article-a1734-abstract Using the Multiple Analysis Approach to Reconstruct Phylogenetic Relationships among Planktonic Foraminifera from Highly Divergent and Length-polymorphic SSU rDNA Sequences]</ref>

Because certain types of foraminifera are found only in certain environments, their fossils can be used to figure out the kind of environment under which ancient marine sediments were deposited; conditions such as salinity, depth, oxygenic conditions, and light conditions can be determined from the different habitat preferences of various species of forams. This allows workers to track changing climates and environmental conditions over time by aggregating information about the foraminifera present.<ref>{{Cite journal|last=Gebhardt|first=Holger|date=1997-02-01|title=Cenomanian to Turonian foraminifera from Ashaka (NE Nigeria): quantitative analysis and palaeoenvironmental interpretation|url=http://www.sciencedirect.com/science/article/pii/S0195667196900476|journal=Cretaceous Research|language=en|volume=18|issue=1|pages=17–36|doi=10.1006/cres.1996.0047|bibcode=1997CrRes..18...17G |issn=0195-6671}}</ref>

In other cases, the relative proportion of planktonic to benthic foraminifera fossils found in a rock can be used as a proxy for the depth of a given locality when the rocks were being deposited.<ref>{{Cite journal|last1=Báldi|first1=Katalin|last2=Benkovics|first2=László|last3=Sztanó|first3=Orsolya|s2cid=129296067|date=2002-05-01|title=Badenian (Middle Miocene) basin development in SW Hungary: subsidence history based on quantitative paleobathymetry of foraminifera|journal=International Journal of Earth Sciences|language=en|volume=91|issue=3|pages=490–504|doi=10.1007/s005310100226|bibcode=2002IJEaS..91..490B|issn=1437-3262}}</ref>

[[File:Planktic foraminifera microfossils from southern Maryland.png|thumb|upright=2|left|Ten species of planktic foraminifera [[microfossil]]s from [[Paleocene-Eocene Thermal Maximum]] (PETM) sediments in southern Maryland.<ref>Robinson, Marci (2021) [https://www.usgs.gov/media/images/planktic-foraminifera-southern-maryland Planktic Foraminifera from Southern Maryland] ''United States Geological Survey''.</ref> The scale bars measure 150 microns (0.015 cm). Each specimen is similar in size to a grain of sand.]]

[[File:65 Myr Climate Change.png|thumb|upright=1.85|Climate change during the last 65 million years as expressed by the [[oxygen isotope]] composition of benthic foraminifera. The Paleocene-Eocene thermal maximum is characterized by a brief but prominent excursion, attributed to rapid warming.<ref>{{cite journal | last1=Zachos | first1=James C. | last2=Shackleton | first2=Nicholas J. | last3=Revenaugh | first3=Justin S. | last4=Pälike | first4=Heiko | last5=Flower | first5=Benjamin P. | title=Climate Response to Orbital Forcing Across the Oligocene-Miocene Boundary | journal=Science | publisher=American Association for the Advancement of Science (AAAS) | volume=292 | issue=5515 | date=2001-04-13 | issn=0036-8075 | doi=10.1126/science.1058288 | pages=274–278| pmid=11303100 | bibcode=2001Sci...292..274Z | s2cid=38231747 | url=http://doc.rero.ch/record/13507/files/PAL_E303.pdf }}</ref><ref>Raymo, M. E. and Lisiecki, L. E. (2005) "A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records", ''Paleoceanography'', '''20''': PA1003.</ref><ref>{{cite journal | last1=Petit | first1=J. R. | last2=Jouzel | first2=J. | last3=Raynaud | first3=D. | last4=Barkov | first4=N. I. | last5=Barnola | first5=J.-M. | last6=Basile | first6=I. | last7=Bender | first7=M. | last8=Chappellaz | first8=J. | last9=Davis | first9=M. | last10=Delaygue | first10=G. | last11=Delmotte | first11=M. | last12=Kotlyakov | first12=V. M. | last13=Legrand | first13=M. | last14=Lipenkov | first14=V. Y. | last15=Lorius | first15=C. | last16=PÉpin | first16=L. | last17=Ritz | first17=C. | last18=Saltzman | first18=E. | last19=Stievenard | first19=M. | title=Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica | journal=Nature | publisher=Springer Science and Business Media LLC | volume=399 | issue=6735 | year=1999 | issn=0028-0836 | doi=10.1038/20859 | pages=429–436| bibcode=1999Natur.399..429P | s2cid=204993577 | url=http://www.escholarship.org/uc/item/7rx4413n }}</ref>]]

{{clear}}

Since at least 1997, the [[Paleocene–Eocene thermal maximum]] (PETM) has been investigated as an analogy for understanding the [[effects of global warming]] and of massive carbon inputs to the ocean and atmosphere, including [[ocean acidification]].<ref name=Dickens1>{{cite journal | author = Dickens, G.R. | author2=Castillo, M.M. | author3=Walker, J.C.G. | year = 1997 | title = A blast of gas in the latest Paleocene; simulating first-order effects of massive dissociation of oceanic methane hydrate | journal =  Geology | volume = 25 | issue = 3 | pages = 259–262| doi=10.1130/0091-7613(1997)025<0259:abogit>2.3.co;2|pmid=11541226 |bibcode=1997Geo....25..259D | s2cid=24020720 }}</ref> Humans today emit about 10 Gt of carbon (about 37 Gt CO2e) per year, and at that rate will release a comparable amount to the PETM in about one thousand years. A main difference is that during the PETM the planet was ice-free, as the [[Drake Passage]] had not yet opened and the [[Central American Seaway]] had not yet closed.<ref>{{cite web|url=http://www.realclimate.org/index.php/archives/2009/08/petm-weirdness/|title=PETM Weirdness|year=2009|publisher=RealClimate|access-date=2016-02-03|archive-url=https://web.archive.org/web/20160212041029/http://www.realclimate.org/index.php/archives/2009/08/petm-weirdness|archive-date=2016-02-12|url-status=live}}</ref> Although the PETM is now commonly held to be a case study for global warming and massive carbon emission, the cause, details, and overall significance of the event remain uncertain.<ref name=McInerney2011>{{cite journal
| author = McInherney, F.A. | author2 = Wing, S. | title = A perturbation of carbon cycle, climate, and biosphere with implications for the future | year = 2011 | journal = Annual Review of Earth and Planetary Sciences | volume = 39 | pages = 489–516 | doi = 10.1146/annurev-earth-040610-133431 | bibcode = 2011AREPS..39..489M | url = http://www.whoi.edu/fileserver.do?id=136084&pt=2&p=148709 | access-date = 2016-02-03 | archive-url = https://web.archive.org/web/20160914003526/http://www.whoi.edu/fileserver.do?id=136084&pt=2&p=148709 | archive-date = 2016-09-14 | url-status = live}}</ref><ref name=Zeebe2009>{{cite journal | author = Zeebe, R. | author2=Zachos, J.C. | author3=Dickens, G.R. | title = Carbon dioxide forcing alone insufficient to explain Palaeocene–Eocene Thermal Maximum warming | year = 2009 | journal = Nature Geoscience | volume = 2 |issue=8 | pages = 576–580 | doi = 10.1038/ngeo578 |bibcode=2009NatGe...2..576Z|citeseerx=10.1.1.704.7960 }}</ref><ref>Marci M Robinson (2022) [https://www.usgs.gov/programs/climate-research-and-development-program/news/ancient-microfossils-are-key-future-climate Ancient microfossils are the key to future climate recovery] ''United States Geological Survey''. {{PD-notice}}</ref><ref name=Babila2022>{{cite journal | last1=Babila | first1=Tali L. | last2=Penman | first2=Donald E. | last3=Standish | first3=Christopher D. | last4=Doubrawa | first4=Monika | last5=Bralower | first5=Timothy J. | last6=Robinson | first6=Marci M. | last7=Self-Trail | first7=Jean M. | last8=Speijer | first8=Robert P. | last9=Stassen | first9=Peter | last10=Foster | first10=Gavin L. | last11=Zachos | first11=James C. | title=Surface ocean warming and acidification driven by rapid carbon release precedes Paleocene-Eocene Thermal Maximum | journal=Science Advances | publisher=American Association for the Advancement of Science (AAAS) | volume=8 | issue=11 | date=2022-03-18 | pages=eabg1025 | issn=2375-2548 | doi=10.1126/sciadv.abg1025| pmid=35294237 | pmc=8926327 | bibcode=2022SciA....8G1025B | s2cid=247498325 | url=https://lirias.kuleuven.be/handle/20.500.12942/694229 }}</ref>

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[[File:Neoflabellina reticulata Säureaufschluss Lundin 2018.tif|thumb|left|''[[Neoflabellina|Neoflabellina reticulata]]'' from chalk of [[Rügen]], Northeastern Germany. Length:1.2 mm, Age: Upper lower [[Maastrichtian]]]]

Foraminifera have significant application in the field of [[biostratigraphy]]. Due to their small size and hard shells, foraminifera may be preserved in great abundance and with high quality of preservation; due to their complex morphology, individual species are easily recognizable. Foraminifera species in the fossil record have limited ranges between the species' first evolution and their disappearance; stratigraphers have worked out the successive changes in foram assemblages throughout much of the [[Phanerozoic]]. As such, the assemblage of foraminifera within a given locality can be analyzed and compared to known dates of appearance and disappearance in order to narrow down the age of the rocks. This allows paleontologists to interpret the age of [[sedimentary rock]]s when [[radiometric dating]] is not applicable.<ref>{{Cite web|last=Australia|first=c\=AU\;o\=Australia Government\;ou\=Geoscience|date=2014-05-15|title=Biostratigraphy|url=https://www.ga.gov.au/scientific-topics/disciplines/biostratigraphy|access-date=2020-07-20|website=ga.gov.au|language=EN}}</ref> This application of foraminifera was discovered by [[Alva C. Ellisor]] in 1920.<ref>{{Cite journal|last1=Cushman|first1=Joseph A.|last2=Ellisor|first2=Alva C.|date=1945-01-01|title=The Foraminiferal Fauna of the Anahuac Formation|journal=Journal of Paleontology|volume=19|issue=6|pages=545–572|jstor=1299203}}</ref>

[[File:Peneroplid thin section PP.jpg|thumb|right|[[Thin section]] of a [[Peneroplidae|peneroplid]] foraminiferan from [[Holocene]] lagoonal sediment in Rice Bay, [[San Salvador Island]], Bahamas.  Scale bar 100 micrometres]]

Calcareous fossil foraminifera are formed from elements found in the ancient seas where they lived.  Thus, they are very useful in [[paleoclimatology]] and [[paleoceanography]].  They can be used, as a climate [[Proxy (climate)|proxy]], to reconstruct past climate by examining the [[stable isotope]] ratios and trace element content of the shells (tests). Global temperature and ice volume can be revealed by the isotopes of oxygen, and the history of the [[carbon cycle]] and oceanic productivity by examining the stable isotope ratios of carbon;<ref name="Zachos et al.">{{Cite journal|last=Zachos|first=J.C.|author2=Pagani, M.|author3=Sloan, L.|author4=Thomas, E.|author5=Billups, K.|s2cid=2365991|year=2001|title=Trends, Rhythms, and Aberrations in Global Climate, 65 Ma to Present|journal=Science|volume=292|issue=5517|pages=686–693|bibcode=2001Sci...292..686Z|doi=10.1126/science.1059412|pmid=11326091|url=http://doc.rero.ch/record/13508/files/PAL_E304.pdf }}</ref> see [[δ18O]] and [[δ13C]].  The concentration of trace elements, like [[strontium]] (Sr),<ref>{{cite journal|last=Keul|first=Nina|author2=Langer, G.|author3=Thoms, S.|author4=de Nooijer, L.J.|author5=Reichart, G.J.|author6=Bijma, J.|date=April 2017|title= Exploring foraminiferal Sr/Ca as a new carbonate system proxy|journal= Geochimica et Cosmochimica Acta|volume=202 |pages=374–386 |doi=10.1016/j.gca.2016.11.022|bibcode=2017GeCoA.202..374K |hdl=1874/380107 |url=https://epic.awi.de/id/eprint/42473/1/Keul_et_al-MS-accepted.pdf }}</ref> [[magnesium]] (Mg),<ref>{{cite journal|last=Branson|first=Oscar|author2=Redfern, Simon A.T.|author3=Tyliszczak, Tolek|author4=Sadekov, Aleksey|author5=Langer, Gerald|author6=Kimoto, Katsunori|author7=Elderfield, Henry|date=December 2013|title=The coordination of Mg in foraminiferal calcite|journal=Earth and Planetary Science Letters|volume=383|pages=134–141|bibcode=2013E&PSL.383..134B|doi=10.1016/j.epsl.2013.09.037|doi-access=free}}</ref> [[lithium]] (Li)<ref>{{cite journal|last=Misra|first=S.|author2=Froelich, P. N.|s2cid=42591236|date=26 January 2012|title=Lithium Isotope History of Cenozoic Seawater: Changes in Silicate Weathering and Reverse Weathering|journal=Science|volume=335|issue=6070|pages=818–823|bibcode=2012Sci...335..818M|doi=10.1126/science.1214697|pmid=22282473|doi-access=free}}</ref> and [[boron]] (B),<ref>{{cite journal|last=Hemming|first=N.G.|author2=Hanson, G.N.|date=January 1992|title=Boron isotopic composition and concentration in modern marine carbonates|journal=Geochimica et Cosmochimica Acta|volume=56|issue=1|pages=537–543|bibcode=1992GeCoA..56..537H|doi=10.1016/0016-7037(92)90151-8}}</ref> also hold a wealth of information about global temperature cycles, continental weathering, and the role of the ocean in the global carbon cycle. Geographic patterns seen in the fossil records of planktonic forams are also used to reconstruct ancient [[ocean current]]s.

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==Modern uses==
The [[oil industry]] relies heavily on [[microfossil]]s such as forams to find potential hydrocarbon deposits.<ref name="Boardman">{{cite book |last1=Boardman |first1=R.S. |first2=A.H. |last2=Cheetham |first3=A.J. |last3=Rowell |title=Fossil Invertebrates |publisher=Wiley |year=1987 |isbn=978-0865423022 }}</ref>[[File:Ammonia beccarii.jpg|thumbnail|right|''[[Ammonia (genus)|Ammonia beccarii]]'', a benthic foram from the [[North Sea]].]] For the same reasons they make useful biostratigraphic markers, living foraminiferal assemblages have been used as [[bioindicator]]s in coastal environments, including indicators of coral reef health.  Because calcium carbonate is susceptible to dissolution in acidic conditions, foraminifera may be particularly affected by changing climate and [[ocean acidification]]. [[File:2085f Japon Hatoma.jpg|thumbnail|right|Foraminifera ''Baculogypsina sphaerulata'' of Hatoma Island, Japan. Field width 5.22 mm]]

Foraminifera have many uses in [[petroleum|petroleum exploration]] and are used routinely to interpret the ages and paleoenvironments of sedimentary strata in oil wells.<ref name="Jones1996">{{cite book |first=R.W. |last=Jones |title=Micropalaeontology in petroleum exploration |url=https://books.google.com/books?id=a5pPAQAAIAAJ |year=1996 |publisher=Clarendon Press |isbn=978-0-19-854091-5}}</ref> Agglutinated fossil foraminifera buried deeply in sedimentary basins can be used to estimate thermal maturity, which is a key factor for petroleum generation. The [[Foraminiferal Colouration Index]]<ref name="McNeil1996">{{cite book |first1=D.H. |last1=McNeil |first2=D.R. |last2=Issler |first3=L.R. |last3=Snowdon |title=Colour Alteration, Thermal Maturity, and Burial Diagenesis in Fossil Foraminifers |url=https://books.google.com/books?id=x_WfAQAACAAJ |year=1996 |publisher=Geological Survey of Canada |isbn=978-0-660-16451-9 |volume=499 |series=Geological Survey of Canada Bulletin}}</ref> (FCI) is used to quantify colour changes and estimate burial temperature.  FCI data is particularly useful in the early stages of petroleum generation (about 100&nbsp;°C).

Foraminifera can also be used in [[archaeology]] in the [[Provenance|provenancing]] of some stone raw material types. Some stone types, such as [[limestone]], are commonly found to contain fossilised foraminifera.  The types and concentrations of these fossils within a sample of stone can be used to match that sample to a source known to contain the same "fossil signature".<ref>{{Cite journal|last1=Wilkinson|first1=Ian P.|last2=Williams|first2=Mark|last3=Young|first3=Jeremy R.|last4=Cook|first4=Samantha R.|last5=Fulford|first5=Michael G.|last6=Lott|first6=Graham K.|date=2008-08-01|title=The application of microfossils in assessing the provenance of chalk used in the manufacture of Roman mosaics at Silchester|url=http://www.sciencedirect.com/science/article/pii/S0305440308000599|journal=Journal of Archaeological Science|language=en|volume=35|issue=8|pages=2415–2422|doi=10.1016/j.jas.2008.03.010|bibcode=2008JArSc..35.2415W |issn=0305-4403}}</ref>

==Gallery==
<gallery>
File:3339c Croatie Pag.jpg|Foraminifera of Pag Island, Adriatic Sea -60 m, field width 5.5&nbsp;mm
File:3339d Croatie Pag.jpg|Foraminifera of Pag Island, Adriatic Sea -60 m, field width 5.5&nbsp;mm
File:3339e Croatie Pag.jpg|Foraminifera of Pag Island, Adriatic Sea -60 m, field width 5.5&nbsp;mm
File:3339f Croatie Pag.jpg|Foraminifera of Pag Island, Adriatic Sea -60 m, field width 5.5&nbsp;mm
File:2966g Bali.jpg|Foraminifera of Indian Ocean, south-eastern coast of Bali, field width 5.5&nbsp;mm
File:2966j Bali.jpg|Foraminifera of Indian Ocean, south-eastern coast of Bali, field width 5.5&nbsp;mm
File:2966k Bali.jpg|Foraminifera of Indian Ocean, south-eastern coast of Bali, field width 5.5&nbsp;mm
File:Foraminifères de Ngapali.jpg|Foraminifera in Ngapali, Myanmar, field width 5.22&nbsp;mm
File:3579h R Indonesie.jpg|Foraminifera ''Heterostegina depressa'', field width 4.4&nbsp;mm
</gallery>

==References==<!-- SystBiol55:848 -->
{{Reflist}}

==External links==
{{Commons category|Foraminifera}}
{{Wikispecies}}
{{Wiktionary|Foraminifera|foraminifera}}

;General information:
* [http://www.ucmp.berkeley.edu/index.html The University of California Museum of Paleontology] website has an [http://www.ucmp.berkeley.edu/foram/foramintro.html Introduction to the Foraminifera]
* Researchers at the University of South Florida developed a system [http://www.marine.usf.edu/reefslab/foramcd/html_files/titlepage.htm using Foraminifera for monitoring coral reef environments] {{Webarchive|url=https://web.archive.org/web/20210115180644/http://www.marine.usf.edu/reefslab/foramcd/html_files/titlepage.htm |date=15 January 2021 }}
* University College London's [http://www.ucl.ac.uk/GeolSci/micropal/foram.html micropaleontology site] has an overview of Foraminifera, including many high-quality [[Scanning electron microscope|SEM]]s
* [http://paleopolis.rediris.es/cg/CG2006_M02/index.html Illustrated glossary of terms used in foraminiferal research] {{Webarchive|url=https://web.archive.org/web/20120621210842/http://paleopolis.rediris.es/cg/CG2006_M02/index.html |date=21 June 2012 }} is the Lukas Hottinger's glossary published in the OA e-journal [http://paleopolis.rediris.es/cg/uk-index.html "Carnets de Géologie – Notebooks on Geology"] {{Webarchive|url=https://web.archive.org/web/20170629094050/http://paleopolis.rediris.es/cg/uk-index.html |date=29 June 2017 }}
* [https://web.archive.org/web/20070810004729/http://www.paleontology.uni-bonn.de/frame02.htm Information on Foraminifera] Martin Langer's Micropaleontology Page
* [http://ethomas.web.wesleyan.edu/BFhandout.htm Benthic Foraminifera information] from the 2005 Urbino Summer School of Paleoclimatology

;Online flip-books:
* [http://fr.calameo.com/read/000023034b9de489f0c3c Illustrated glossary of terms used in foraminiferal research] by [[Lukas Hottinger]] (alternative version of the one published in [http://paleopolis.rediris.es/cg/uk-index.html "Carnets de Géologie – Notebooks on Geology"] {{Webarchive|url=https://web.archive.org/web/20170629094050/http://paleopolis.rediris.es/cg/uk-index.html |date=29 June 2017 }})

;Resources:
* [http://www.mikrotax.org/pforams/ pforams@mikrotax] – an online database detailing the taxonomy of planktonic foraminifera
* The [https://web.archive.org/web/20060620040556/http://www.bowserlab.org/starsand.html star*sand project] (part of [https://web.archive.org/web/20080609213132/http://starcentral.mbl.edu/mv/portal.php?pagetitle=index micro*scope]) is a cooperative database of information about Foraminifera
* [http://webdb2.museum.tohoku.ac.jp/e-foram/ 3D models] of forams, generated by [[X-ray tomography]]
* [https://web.archive.org/web/19981205122129/http://www.chronos.org/ CHRONOS] has [https://web.archive.org/web/20061115112221/http://portal.chronos.org/gridsphere/gridsphere?cid=res_foram several Foraminifera resources], including a [https://web.archive.org/web/20060512035435/http://portal.chronos.org/gridsphere/gridsphere?cid=res_taxondb taxon search page] and a [https://web.archive.org/web/20120328221949/http://portal.chronos.org/gridsphere/gridsphere?cid=micropaleo micro-paleo section] NB Most of this content is now included in the pforams@mikrotax website
* [http://www.eforams.org eForams] is a web site focused on Foraminifera and modeling of foraminiferal shells
* [http://www.foraminifera.eu Foraminifera Gallery] Illustrated catalog of recent and fossil Foraminifera by genus and locality
* {{cite web |title=''Foraminifera'' |work=NCBI Taxonomy Browser |url=https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=29178&lvl=1 |id=29178}}

{{Eukaryota}}
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[[Category:Foraminifera| ]]
[[Category:Bikont subphyla]]
[[Category:Extant Cambrian first appearances]]
[[Category:Great Pyramid of Giza]]