Editing Acritarch

{{short description|Microfossils}}
{{Distinguish|Antiarchi}}
{{Use dmy dates|date=March 2017}}
{{Automatic taxobox
| name = Acritarchs
| fossil_range = 
| image = Doushantou Embryo Yinetal2007.jpg
| image_caption = A supposed [[Ediacaran]] [[embryo]] contained within an acritarch from the [[Doushantuo Formation]]
| taxon = Acritarcha
| authority = Evitt, 1963
| display_parents = 2
| subdivision_ranks = 
| subdivision = 
| synonyms = * Hystrichospheres ''[[pro parte|p.p.]]''
}}
[[File:Acritarch from the Weng'an biota.jpg|thumb|upright=1.2|{{center|Acritarch from the Weng'an biota<br />c. 570–609 [[MYA (unit)|mya]] {{hsp}}<ref>{{cite journal |doi = 10.1144/jgs2016-142|title = The Weng'an Biota (Doushantuo Formation): An Ediacaran window on soft-bodied and multicellular microorganisms|year = 2017|last1 = Cunningham|first1 = John A.|last2 = Vargas|first2 = Kelly|last3 = Yin|first3 = Zongjun|last4 = Bengtson|first4 = Stefan|last5 = Donoghue|first5 = Philip C. J.|journal = Journal of the Geological Society|volume = 174|issue = 5|pages = 793–802|bibcode = 2017JGSoc.174..793C|doi-access = free|hdl = 1983/d874148a-f20e-498a-97d2-379b3feaa18a|hdl-access = free}}</ref>}}]]

'''Acritarchs''' ({{etymology|gre|achritos|uncertain||arché|origin}})<ref>{{cite book|last1=Jain|first1=Sreepat|date=2020|chapter=Acritarchs|title=Fundamentals of Invertebrate Palaeontology|series=Springer Geology|publisher=Springer|location=New Delhi|doi=10.1007/978-81-322-3962-8_2|pages=27–42}}</ref> are organic [[microfossil]]s, known from the [[Precambrian]] to the present. The classification is a catch all term used to refer to any organic microfossils that cannot be assigned to other groups. Their diversity reflects major ecological events such as the appearance of predation and the [[Cambrian explosion]]. Many acritarchs likely represent [[Microbial cyst|resting cysts]] of single-celled marine [[phytoplanktonic]] [[algae]], similar to those produced by living [[dinoflagellate]]s.<ref>{{Cite journal |last=Servais |first=Thomas |last2=Perrier |first2=Vincent |last3=Danelian |first3=Taniel |last4=Klug |first4=Christian |last5=Martin |first5=Ronald |last6=Munnecke |first6=Axel |last7=Nowak |first7=Hendrik |last8=Nützel |first8=Alexander |last9=Vandenbroucke |first9=Thijs R.A. |last10=Williams |first10=Mark |last11=Rasmussen |first11=Christian M.Ø. |date=September 2016 |title=The onset of the 'Ordovician Plankton Revolution' in the late Cambrian |url=https://doi.org/10.1016/j.palaeo.2015.11.003 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=458 |pages=12–28 |doi=10.1016/j.palaeo.2015.11.003 |issn=0031-0182}}</ref>

==Definition==
Acritarchs were originally defined as non-[[acid]] soluble (i.e. non-[[carbonate]], non-[[siliceous]]) organic-walled microfossils consisting of a central cavity, and whose biological affinities cannot be determined with certainty.<ref>{{Cite journal|last=Evitt|first=William R.|date=1963|title=A discussion and proposals concerning fossil dinoflagellates, hystrichospheres, and acritarchs, II|url=http://www.pnas.org/content/pnas/49/3/298.full.pdf|journal=Proceedings of the National Academy of Sciences|volume=49|issue=3|pages=298–302|via=PNAS|doi=10.1073/pnas.49.3.298|pmid=16591055|pmc=299818|bibcode=1963PNAS...49..298E|doi-access=free}}</ref><ref>{{cite journal |doi = 10.1111/j.1469-185X.1993.tb01241.x|title = Acritarchsa Review|year = 1993|last1 = Martin|first1 = Francine|journal = Biological Reviews|volume = 68|issue = 4|pages = 475–537|s2cid = 221527533}}</ref><ref>{{cite journal |doi = 10.1016/0034-6667(94)00148-D|title = Review of biological affinities of Paleozoic acid-resistant, organic-walled eukaryotic algal microfossils (Including "acritarchs")|year = 1995|last1 = Colbath|first1 = G.Kent|last2 = Grenfell|first2 = Hugh R.|journal = Review of Palaeobotany and Palynology|volume = 86|issue = 3–4|pages = 287–314| bibcode=1995RPaPa..86..287C }}</ref> Most commonly they are composed of thermally altered acid insoluble carbon compounds ([[kerogen]]).

Acritarchs may include the remains of a wide range of quite different kinds of organisms—ranging from the egg cases of small [[metazoan]]s to resting cysts of many kinds of [[chlorophyta]] (green algae). It is likely that most acritarch species from the [[Paleozoic]] represent various stages of the life cycle of algae that were ancestral to the [[dinoflagellates]].<ref>{{Cite journal|last1=Colbath|first1=G.Kent|last2=Grenfell|first2=Hugh R.|date=1995|title=Review of biological affinities of Paleozoic acid-resistant, organic-walled eukaryotic algal microfossils (including "acritarchs")|journal=Review of Palaeobotany and Palynology|volume=86|issue=3–4|pages=287–314|doi=10.1016/0034-6667(94)00148-d|bibcode=1995RPaPa..86..287C |issn=0034-6667}}</ref> The nature of the organisms associated with [[Precambrian]] acritarchs is generally not well understood, though many are probably related to unicellular marine [[alga]]e. In theory, when the biological source (taxon) of an acritarch does become known, that particular microfossil is removed from the acritarchs and classified with its proper group.{{citation needed|date=November 2023}}

While the [[biological classification|classification]] of acritarchs into [[form taxon|form genera]] is entirely artificial, it is not without merit, as the form taxa show traits similar to those of genuine [[taxon|taxa]]—for example an '[[cambrian explosion|explosion]]' in the [[Cambrian]] and a [[mass extinction]] at the [[Permian-Triassic extinction event|end]] of the [[Permian]].{{citation needed|date=November 2023}}

==Classification==

The informal group, Acritarcha Evitt 1963, was originally divided into the Subgroups: Acanthomorphitae, Polygonomorphitae, Prismatomorphitae, Oömorphitae, Netromorphitae, Dinetromorphitae, Stephanomorphitae, Pteromorphitae, Herkomorphitae, Platymorphitae, Sphaeromorphitae, and Disphaeromorphitae.<ref>{{cite journal |last1=Strother |first1=Paul |title=Palynomorph focus: Acritarchs. |journal=AASP – The Palynological Society Newsletter |volume=56 |issue=3 |pages=29–33}}</ref><ref>{{cite web |last1=Strother |first1=Paul |title=Acritarchs |url=https://palynology.org/what-is-palynology/palynomorphs/acritarchs/ |website=The Palynological Society |publisher=AASP-The Palynological Society |access-date=12 July 2024}}</ref><ref>{{Cite journal|last=Evitt|first=William R.|date=1963|title=A discussion and proposals concerning fossil dinoflagellates, hystrichospheres, and acritarchs, II|url=http://www.pnas.org/content/pnas/49/3/298.full.pdf|journal=Proceedings of the National Academy of Sciences|volume=49|issue=3|pages=298–302|via=PNAS|doi=10.1073/pnas.49.3.298|pmid=16591055|pmc=299818|bibcode=1963PNAS...49..298E|doi-access=free}}</ref>

Acritarchs were most likely [[eukaryote]]s. While archaea and bacteria ([[prokaryotes]]) usually produce simple fossils of a very small size, eukaryotic unicellular fossils are usually larger and more complex, with external morphological projections and ornamentation such as spines and hairs that only eukaryotes can produce; as most acritarchs have external projections (e.g., hair, spines, thick cell membranes, etc.), they are predominantly eukaryotes, although simple eukaryote acritarchs also exist.<ref>{{Cite journal| doi = 10.1038/463885a| pmid = 20164911| year = 2010| last1 = Buick | first1 = R. .| title = Early life: Ancient acritarchs| volume = 463| issue = 7283| pages = 885–886| journal = Nature |bibcode = 2010Natur.463..885B | doi-access = free}}</ref>

The recent application of [[atomic force microscopy]], [[confocal microscopy]], [[Raman spectroscopy]], and other sophisticated analytic techniques to the study of the ultrastructure, life history, and systematic affinities of mineralized, but originally organic-walled microfossils,<ref>{{cite journal |doi = 10.1073/pnas.142310299|title = Atomic force microscopy of Precambrian microscopic fossils|year = 2002|last1 = Kempe|first1 = A.|last2 = Schopf|first2 = J. W.|last3 = Altermann|first3 = W.|last4 = Kudryavtsev|first4 = A. B.|last5 = Heckl|first5 = W. M.|journal = Proceedings of the National Academy of Sciences|volume = 99|issue = 14|pages = 9117–9120|pmid = 12089337|pmc = 123103|bibcode = 2002PNAS...99.9117K|doi-access = free}}</ref><ref>{{cite journal |doi = 10.1016/j.precamres.2005.07.002|title = Focussed ion beam preparation and in situ nanoscopic study of Precambrian acritarchs|year = 2005|last1 = Kempe|first1 = A.|last2 = Wirth|first2 = R.|last3 = Altermann|first3 = W.|last4 = Stark|first4 = R.|last5 = Schopf|first5 = J.|last6 = Heckl|first6 = W.|journal = Precambrian Research|volume = 140|issue = 1–2|pages = 36–54|bibcode = 2005PreR..140...36K}}</ref><ref>{{cite journal |doi = 10.1016/j.precamres.2005.05.006|title = Combined micro-Fourier transform infrared (FTIR) spectroscopy and micro-Raman spectroscopy of Proterozoic acritarchs: A new approach to Palaeobiology|year = 2005|last1 = Marshall|first1 = C.|last2 = Javaux|first2 = E.|last3 = Knoll|first3 = A.|last4 = Walter|first4 = M.|journal = Precambrian Research|volume = 138|issue = 3–4|pages = 208–224|bibcode = 2005PreR..138..208M}}</ref><ref>{{cite journal |doi = 10.4202/app.2008.0060|title = Spore-Like Bodies in Some Early Paleozoic Acritarchs: Clues to Chlorococcalean Affinities|year = 2009|last1 = Kaźmierczak|first1 = Józef|last2 = Kremer|first2 = Barbara|journal = Acta Palaeontologica Polonica|volume = 54|issue = 3|pages = 541–551|doi-access = free}}</ref><ref>{{cite journal |doi = 10.1666/09-134.1|title = Confocal laser scanning microscopy and Raman imagery of the late Neoproterozoic Chichkan microbiota of South Kazakhstan|year = 2010|last1 = Schopf|first1 = J. William|last2 = Kudryavtsev|first2 = Anatoliy B.|last3 = Sergeev|first3 = Vladimir N.|journal = Journal of Paleontology|volume = 84|issue = 3|pages = 402–416| bibcode=2010JPal...84..402S |s2cid = 130041483}}</ref> has shown that some acritarchs are actually fossilized [[microalgae]]. In the end, it may well be, as Moczydłowska et al. suggested in 2011, that many acritarchs will, in fact, turn out to be algae.<ref>{{cite journal |doi = 10.1111/j.1475-4983.2011.01054.x|title = Proterozoic phytoplankton and timing of Chlorophyte algae origins|year = 2011|last1 = Moczydłowska|first1 = Małgorzata|last2 = Landing|first2 = ED|last3 = Zang|first3 = Wenlong|last4 = Palacios|first4 = Teodoro|journal = Palaeontology|volume = 54|issue = 4|pages = 721–733| bibcode=2011Palgy..54..721M |doi-access = free}}</ref><ref name=Chamberlain2016>{{cite journal |doi = 10.3390/geosciences6040057|title = A Mineralized Alga and Acritarch Dominated Microbiota from the Tully Formation (Givetian) of Pennsylvania, USA|year = 2016|last1 = Chamberlain|first1 = John|last2 = Chamberlain|first2 = Rebecca|last3 = Brown|first3 = James|journal = Geosciences|volume = 6|issue = 4|page = 57|bibcode = 2016Geosc...6...57C|doi-access = free}} [[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>

==Occurrence==

Acritarchs are found in sedimentary rocks from the present back into the [[Archean]].<ref>{{cite journal |year=2003 |title=Montenari, M. & Leppig, U. (2003): The Acritarcha: their classification morphology, ultrastructure and palaeoecological/palaeogeographical distribution. |journal=Paläontologische Zeitschrift |volume=77 |pages=173–194 |doi=10.1007/bf03004567 |s2cid=127238427}}</ref> They are typically isolated from siliciclastic sedimentary rocks using [[hydrofluoric acid]] but are occasionally extracted from carbonate-rich rocks. They are excellent candidates for index fossils used for dating rock formations in the [[Palaeozoic|Paleozoic]] Era and when other fossils are not available. Because most acritarchs are thought to be marine (pre-Triassic), they are also useful for palaeoenvironmental interpretation.

The Archean and earliest [[Proterozoic]] microfossils termed "acritarchs" may actually be prokaryotes. The earliest eukaryotic acritarchs known ({{As of|2020|lc=y}}) are from between 1950 and 2150 million years ago.<ref>{{cite journal |last1=Yin |first1=Leiming |title=Microfossils from the Paleoproterozoic Hutuo Group, Shanxi, North China: Early evidence for eukaryotic metabolism |journal=Precambrian Research |volume=342 |pages=105650 |date=Feb 2020 |doi=10.1016/j.precamres.2020.105650|bibcode=2020PreR..34205650Y |doi-access=free }}</ref>

==Diversity==

At about 1 billion years ago the organisms responsible for acritarchs started to increase in abundance, diversity, size, complexity of shape, and especially, the size and number of spines. Their populations crashed during periods of extensive worldwide glaciations that covered the majority of the planet, but they proliferated in the Cambrian explosion and reached their highest diversity in the [[Paleozoic]]. The increased spininess 1000 million years ago possibly resulted from the need for defense against predators, especially predators large enough to swallow them or tear them apart. Other groups of small organisms from the [[Neoproterozoic]] era also show signs of anti-predator defenses.<ref name="Bengtson2002OriginsOfPredation">{{Cite encyclopedia
 | author=Bengtson, S.
 | year=2002
 | chapter=Origins and early evolution of predation
 | encyclopedia=The Paleontological Society Papers
 | volume=8
 | title=The fossil record of predation
 |editor=Kowalewski, M. |editor2=Kelley, P.H.
 | pages=289–317
 | publisher=The Paleontological Society
 | chapter-url=http://www.nrm.se/download/18.4e32c81078a8d9249800021552/Bengtson2002predation.pdf
 | access-date=29 December 2014
 }}</ref>

Further evidence that acritarchs were subject to herbivory around this time comes from a consideration of taxon longevity. The abundance of planktonic organisms that evolved between 1,700 and 1,400 million years ago was limited by nutrient availability – a situation which limits the origination of new species because the existing organisms are so specialised to their niches, and no other niches are available for occupation. Approximately 1,000 million years ago, species longevity fell sharply, suggesting that predation pressure, probably by protist herbivores, became an important factor. Predation would have kept populations in check, meaning that some nutrients were left unused, and new niches were available for new species to occupy.<ref name=Stanley2008>{{Cite journal| first1 = S. M. | title = Predation defeats competition on the seafloor | journal = Paleobiology | volume = 34 | pages = 1–21| year = 2008| last1 = Stanley | issue = 1 | doi = 10.1666/07026.1| bibcode = 2008Pbio...34....1S | s2cid = 83713101 }}</ref>

==Etymology==
''Acritarch'' was coined in 1963 from the [[Greek (language)|Greek]] ''ákritos'' meaning ''confused'' (''a kritēs'', ''without critic'') and ''archē'' meaning ''origin'' (confer [[wikt:archaic|archaic]]).<ref>definition of [http://dictionary.reference.com/browse/acritarch acritarch] at [[dictionary.com]]</ref>

==Selected genera==
There are over 900 described genera; the following is a partial list, from Fossilid.info.<ref>{{Cite web|url=https://fossiilid.info/10366?mode=in_baltoscandia&lang=en|title=Actipillion}}</ref>

{{Div col}}
* ''[[Acanthodiacrodium]]'' (Ordovician)
* ''[[Acrosphaeridium]]'' (Ordovician)
* ''[[Actipillion]]'' (Ordovician)
* ''[[Akomachra]]'' (Ordovician)
* ''[[Ammonidium]]'' (Silurian)
* ''[[Aranidium]]'' (Cambrian)
* ''[[Arbusculidium]]'' (Cambrian-Ordovician)
* ''[[Archaeodiscina]]'' (Cambrian)
* ''[[Arcosphaeridium]]'' (Ordovician)
* ''[[Aremoricanium]]'' (Ordovician)
* ''[[Arkonia]]'' (Ordovician)
* ''[[Asteridium (acritarch)|Asteridium]]'' (Cambrian)
* ''[[Athabascaella]]'' (Tremadocian, Early Ordovician)
* ''[[Axisphaeridium]]'' (Ordovician)
* ''[[Bacisphaeridium]]'' (Ordovician)
* ''[[Baltisphaeridium]]'' (Cambrian-Silurian)
* ''[[Buedingiisphaeridium]]'' (Ordovician)
* ''[[Caldariola]]'' (Cambrian)
* ''[[Calyxiella]]'' 
* ''[[Celtiberium]]'' 
* ''[[Cephalonyx]]''
* ''[[Ceratophyton]]'' (Cambrian)
* ''[[Cheleutochroa]]'' (Ordovician)
* ''[[Chlamydosphaeridia]]'' (Ordovician)
* ''[[Comasphaeridium]]'' (Ordovician)
* ''[[Coronitesta]]'' (Ordovician)
* ''[[Coryphidium]]'' (Ordovician)
* ''[[Costatilobus]]'' (Ordovician)
* ''[[Cristallinium]]'' (Cambrian)
* ''[[Cycloposphaeridium]]'' (Ordovician)
* ''[[Cymatiogalea]]'' (Cambrian)
* ''[[Cymatiosphaera]]'' (Cambrian-Ordovician)
* ''[[Dactylofusa]]'' (Ordovician)
* ''[[Dasydiacrodium]]'' (Cambrian)
* ''[[Dicommopalla]]'' (Ordovician)
* ''[[Dictyosphaera]]'' (Statherian<ref>{{cite journal |last1=Miao |first1=Lanyun |last2=Moczydłowska |first2=Małgorzata |last3= 
Zhu |first3=Shixing |last4= Zhu |first4=Maoyan |title=New record of organic-walled, morphologically distinct microfossils from the late Paleoproterozoic Changcheng Group in the Yanshan Range, North China |year=2019 |journal=Precambrian Research |volume=321 |issue= |pages=172–198 |doi=10.1016/j.precamres.2018.11.019}}</ref>-Paleozoic)
* ''[[Dictyosphaeridium]]'' (Ordovician)
* ''[[Diexallophasis]]'' (Silurian)
* ''[[Dilatisphaera]]'' (Ordovician)
* ''[[Domasia]]'' (Ordovician-Silurian)
* ''[[Dongyesphaera]]'' (Paleozoic)
* ''[[Elektroriskos]]'' (Cambrian)
* ''[[Elenia (organism)|Elenia]]'' 
* ''[[Eliasum]]'' 
* ''[[Estiastra]]'' (Ordovician)
* ''[[Excultibrachium]]'' (Ordovician)
* ''[[Fimbriaglomerella]]'' 
* ''[[Florisphaeridium]]'' (Ordovician)
* ''[[Globosphaeridium]]'' (Cambrian)
* ''[[Goniosphaeridium]]'' (Cambrian-Ordovician)
* ''[[Gorgonisphaeridium]]'' (Ordovician)
* ''[[Granomarginata]]'' (Cambrian)
* ''[[Gyalorhethium]]'' (Ordovician)
* ''[[Hapsidopalla]]'' (Ordovician)
* ''[[Helosphaeridium]]'' (Ordovician)
* ''[[Impluviculus]]'' (Cambrian)
* ''[[Introvertocystis]]'' (Late Cretaceous)
* ''[[Izhoria (organism)|Izhoria]]'' 
* ''[[Joehvisphaera]]'' (Ordovician)
* ''[[Korilophyton]]'' (Cambrian)
* ''[[Kundasphaera]]'' (Ordovician)
* ''[[Labyrinthosphaeridium]]'' (Ordovician)
* ''[[Lacunosphaeridium]]'' (Ordovician)
* ''[[Ladogella]]'' 
* ''[[Leiofusa]]'' (Cambrian-Silurian)
* ''[[Leiosphaeridia]]'' (Statherian-Present)
* ''[[Leiovalia]]'' (Ordovician)
* ''[[Liepaina]]'' (Cambrian)
* ''[[Liliosphaeridium]]'' (Ordovician)
* ''[[Lophosphaeridium]]'' (Ordovician-Silurian)
* ''[[Lunulidia]]'' 
* ''[[Micrhystridium]]'' (Ordovician-Silurian)
* ''[[Multiplicisphaeridium]]'' (Cambrian-Silurian)
* ''[[Nanocyclopia]]'' (Ordovician)
* ''[[Nodosus (acritarch)|Nodosus]]'' 
* ''[[Oppilatala]]'' (Silurian)
* ''[[Ordovicidium]]'' (Ordovician)
* ''[[Orthosphaeridium]]'' (Ordovician)
* ''[[Ovulum]]'' (Cambrian)
* ''[[Palaeocladophora]]'' (Cambrian)
* ''[[Palaeomonostroma]]'' (Cambrian)
* ''[[Peteinosphaeridium]]'' (Ordovician)
* ''[[Pheoclosterium]]'' (Ordovician)
* ''[[Pirea]]'' (Cambrian)
* ''[[Poikilofusa]]'' 
* ''[[Polyancistrodorus]]'' (Ordovician)
* ''[[Polyedryxium]]'' (Ordovician)
* ''[[Polygonium]]'' (Cambrian-Ordovician)
* ''[[Portalites]]'' (Permian)
* ''[[Priscogaleata]]'' (Ordovician)
* ''[[Priscotheca]]''
* ''[[Protosphaeridium]]'' (Silurian)
* ''[[Pterospermella]]'' 
* ''[[Pterospermopsis]]'' (Ordovician)
* ''[[Pulvinosphaeridium]]'' (Ordovician)
* ''[[Quadrisporites]]'' (Permian)
* ''[[Raplasphaera]]'' (Ordovician)
* ''[[Revinotesta]]'' (Ordovician)
* ''[[Rhopaliophora]]'' (Ordovician)
* ''[[Saharidia]]'' (Ordovician)
* ''[[Salopidium]]'' (Silurian)
* ''[[Satka (acritarch)|Satka]]'' (Paleozoic)
* ''[[Shuiyousphaeridium]]'' (Orosirian-Ediacaran)
* ''[[Skiagia]]'' (Cambrian)
* ''[[Solisphaeridium]]'' (Ordovician)
* ''[[Stellechinatum]]'' (Ordovician)
* ''[[Stelliferidium]]'' (Cambrian)
* ''[[Taeniosphaeridium]]'' (Ordovician)
* ''[[Tasmanites]]'' (Ordovician-Silurian)
* ''[[Tetraporina]]'' (Permian)
* ''[[Timofeevia]]'' (Cambrian-Ordovician)
* ''[[Tranvikium]]'' (Ordovician)
* ''[[Trichosphaeridium]]'' 
* ''[[Tunisphaeridium]]'' (Ordovician-Silurian)
* ''[[Tylotopalla]]'' (Ordovician)
* ''[[Vernanimalcula]]'' (Ediacaran)
* ''[[Veryhachium]]'' (Cambrian-Silurian)
* ''[[Villosacapsula]]'' (Ordovician)
* ''[[Visbysphaera]]'' (Silurian)
* ''[[Volkovia]]''
* ''[[Vulcanisphaera]]'' (Cambrian-Ordovician)
* ''[[Winwaloeusia]]'' (Ordovician)
{{Div col end}}

==See also==
*[[Large ornamented Ediacaran microfossil]]

==References==
{{Reflist}}

== External links ==
* [https://web.archive.org/web/20070222051456/http://www.cimp.ulg.ac.be/Acritarchs.html CIMP Subcommission on Acritarchs]* {{Cite web | url=http://www.cimp.ulg.ac.be/ | title=CIMP Home page| archive-url=https://web.archive.org/web/20070217200459/http://www.cimp.ulg.ac.be/| archive-date=17 February 2007}} Commission Internationale de Microflore du Paléozoique (CIMP), international commission for Palaeozoic palynology.
* {{Cite web | url=http://www.nhm.ac.uk/hosted_sites/tms/ | url-status=dead | title=The Micropalaeontological Society | access-date=12 November 2004 | archive-url=https://web.archive.org/web/20041208230552/http://www.nhm.ac.uk/hosted_sites/tms/ | archive-date=8 December 2004 }}
* {{Cite web | url=http://www.palynology.org/ |title = The Palynological Society}} The American Association of Stratigraphic Palynologists (AASP)

{{Eukaryota}}
{{Taxonbar|from=Q342747}}

[[Category:Acritarchs]]
[[Category:Enigmatic eukaryote taxa]]