Editing Bryozoa (section)

== Taxonomy ==
{{See also|List of bilaterial animal orders}}
[[File:Peronopora080512.JPG|thumb|''Peronopora'', a trepostome bryozoan from the Whitewater Formation (Upper [[Ordovician]]) of eastern [[Indiana]], United States]]
[[File:The Childrens Museum of Indianapolis - Evactinopora bryozoan - detail.jpg|thumb|''Evactinopora'' bryozoan found in Jefferson County, [[Missouri]], United States]]

The phylum was originally called "Polyzoa", but this name was eventually replaced by Ehrenberg's term "Bryozoa".<ref name="Muir-Wood 1955"/><ref name="BeattyBlackwelder1974" /><ref name="Mayr1968BryozoaVersusEctoprocta" /> The name "Bryozoa" was originally applied only to the animals also known as Ectoprocta ({{lit|outside-anus}}),<ref>{{cite book |last=Little |first=W. |author2=Fowler, H.W |author3=Coulson, J. |author4=Onions, C.T. |name-list-style=amp |title=Shorter Oxford English Dictionary |publisher=Oxford University Press |year=1964 |chapter=Ecto- |isbn=978-0-19-860613-0}}</ref> in which the [[anus]] lies outside the "crown" of tentacles. After the discovery of the [[Entoprocta]] ({{lit|inside-anus}}),<ref>{{cite book |last=Little |first=W. |author2=Fowler, H.W. |author3=Coulson, J. |author4=Onions, C.T. |name-list-style=amp |title=Shorter Oxford English Dictionary |publisher=Oxford University Press |year=1964 |chapter=Ento- |isbn=978-0-19-860613-0}}</ref> in which the anus lies within a "crown" of tentacles, the name "Bryozoa" was promoted to [[phylum]] level to include the two [[class (biology)|classes]] Ectoprocta and Entoprocta.<ref name="Halanych2004AnimalPhylogeny">{{cite journal |last=Halanych |first=K.M. |year=2004 |title=The new view of animal phylogeny |journal=Annual Review of Ecology, Evolution, and Systematics |volume=35 |pages=229–256 |url=http://www-fourier.ujf-grenoble.fr/~dpiau/cdem/130124b.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www-fourier.ujf-grenoble.fr/~dpiau/cdem/130124b.pdf |archive-date=2022-10-09 |url-status=live |access-date=2016-08-26 | doi=10.1146/annurev.ecolsys.35.112202.130124}}</ref> However, in 1869 Hinrich Nitsche regarded the two groups as quite distinct for a variety of reasons, and coined the name "Ectoprocta" for Ehrenberg's "Bryozoa".<ref name="FuchsObstSundberg2009ComprMolPhyloOfBryozoa" /><ref name="HausdorfHelmkampfMeyer2007Spiralian Phylogenomics" /> Despite their apparently similar methods of feeding, they differed markedly anatomically; in addition to the different positions of the anus, ectoprocts have hollow tentacles and a [[coelom]], while entoprocts have solid tentacles and no coelom. Hence the two groups are now widely regarded as separate phyla, and the name "Bryozoa" is now synonymous with "Ectoprocta".<ref name="Halanych2004AnimalPhylogeny" /> This has remained the majority view ever since, although most publications have preferred the name "Bryozoa" rather than "Ectoprocta".<ref name="Mayr1968BryozoaVersusEctoprocta">{{cite journal |last=Mayr |first=E. |date=June 1968 |title=Bryozoa versus Ectoprocta |journal=Systematic Zoology |volume=17 |issue=2 |pages=213–216 |jstor=2412368 |doi=10.2307/2412368}}</ref> Nevertheless, some notable scientists have continued to regard the "Ectoprocta" and Entoprocta as close relatives and group them under "Bryozoa".<ref name="HausdorfHelmkampfMeyer2007Spiralian Phylogenomics"/>

The ambiguity about the scope of the name "Bryozoa" led to proposals in the 1960s and 1970s that it should be avoided and the unambiguous term "Ectoprocta" should be used.<ref>{{cite journal |last=Cuffey |first=R. J. |year=1969 |title=Bryozoa versus Ectoprocta – The Necessity for Precision |journal=Systematic Zoology |volume=18 |issue=2 |pages=250–251 |doi=10.2307/2412617 |jstor=2412617 }}</ref> However, the change would have made it harder to find older works in which the phylum was called "Bryozoa", and the desire to avoid ambiguity, if applied consistently to all classifications, would have necessitated renaming of several other phyla and many lower-level groups.<ref name="BeattyBlackwelder1974">{{cite journal |last=Beatty |first=J.A. |year=1974 |title=Names of Invertebrate Phyla |journal=Systematic Zoology |volume=23 |issue=4 |pages=545–547 |jstor=2412472 |doi=10.2307/2412472 |author2=Blackwelder}}</ref> In practice, zoological naming of split or merged groups of animals is complex and not completely consistent.<ref>{{cite journal |last=Ghiselin |first=M.T. |year=1977 |title=On Changing the Names of Higher Taxa |journal=Systematic Zoology |volume=26 |issue=3 |pages=346–349 |jstor=2412681 |doi=10.2307/2412681}}</ref> Works since 2000 have used various names to resolve the ambiguity, including: "Bryozoa",<ref name="RuppertFoxBarnesBryozoa" /><ref name="RichFenton1997Bryozoans" /> "Ectoprocta",<ref name="Nielsen2002PhyloPosOfEntoproctaEctoproctaPhoronidaBrachiopoda" /><ref name="Doherty2001EctoproctaInAnderson" /> "Bryozoa (Ectoprocta)",<ref name="Nielsen2001InEncOfLifeSci" /> and "Ectoprocta (Bryozoa)".<ref>{{cite journal |last1=Yokobori |first1=S. |date=May 2008 |title=Complete nucleotide sequences of mitochondrial genomes of two solitary entoprocts, ''Loxocorone allax'' and ''Loxosomella aloxiata'': Implications for lophotrochozoan phylogeny |journal=Molecular Phylogenetics and Evolution |volume=47 |issue=2 |pages=612–628 |doi=10.1016/j.ympev.2008.02.013 |pmid=18374604 |last2=Iseto |first2=T |last3=Asakawa |first3=S |last4=Sasaki |first4=T |last5=Shimizu |first5=N |last6=Yamagishi |first6=A |last7=Oshima |first7=T |last8=Hirose |first8=E|bibcode=2008MolPE..47..612Y }}</ref> Some have used more than one approach in the same work.<ref>{{cite journal |last=Reynolds |first=K.T. |year=2000 |title=Taxonomically Important Features on the Surface of Floatoblasts in ''Plumatella'' (Bryozoa) |journal=Microscopy and Microanalysis |volume=6 |issue=3 |pages=202–210 |pmid= 10790488 |doi=10.1017/S1431927600000349 |bibcode=2000MiMic...6..202R}} The text begins "Phylum Ectoprocta (Bryozoa) ..."</ref>

The common name "moss animals" is the literal meaning of "Bryozoa", from Greek {{lang|grc|βρυόν}} ('moss') and {{lang|grc|ζῷα}} ('animals'), based on the mossy appearance of encrusting species.<ref>{{cite book | last1=Trumble | first1=W | author2=Brown, L | title=Shorter Oxford English Dictionary | chapter-url=https://archive.org/details/shorteroxfordeng00will_0 | chapter-url-access=registration | publisher=Oxford University Press | year=2002 | isbn=978-0-19-860457-0 | chapter=Bryozoa }}</ref>
<!--[[ITIS]], the Integrated Taxonomic Information System, designates the phylum as "Ectoprocta",<ref name="ITISEctoprocta">{{cite web |url=https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=155470 |title=ITIS Standard Report Page: Ectoprocta |publisher=[[Integrated Taxonomic Information System]] |access-date=2009-08-23}}</ref> referring to the position of the [[anus]] outside the "crown" of feeding tentacles (based on the [[Ancient Greek]] prefix {{lang|grc|ἐκτο}} meaning "outside" and word {{lang|grc|πρωκτος}} meaning "anus").<ref>{{cite book |last=Little |first=W. |author2=Fowler, H.W, Coulson, J. and Onions, C.T. |title=Shorter Oxford English Dictionary |publisher=Oxford University Press |date=1964 |chapter=Ecto- |isbn=0-19-860613-3}}</ref> The term "Bryozoa" (from the Ancient Greek words {{lang-grc|βρυος|bryos|label=none}} meaning "moss" and {{lang-grc|ζωον|zoon|label=none}} meaning "animal") is widely used to refer to Ectoprocta in books and articles.<ref name="Nielsen2002PhyloPosOfEntoproctaEctoproctaPhoronidaBrachiopoda" /> because some species look moss-like.<ref name="SOED1959Bryozoa" /> However, the name "Bryozoa" has also been used for the combination of Ectoprocta with [[Entoprocta]], which are distinguished by having the anus inside a "crown" of tentacles (based on the Ancient Greek prefix {{lang|grc|ἐντο}} meaning "inside" and word {{lang|grc|πρωκτος}} meaning "anus"),<ref>{{cite book |last=Little |first=W. |author2=Fowler, H.W, Coulson, J. and Onions, C.T. |title=Shorter Oxford English Dictionary |publisher=Oxford University Press |date=1964 |chapter=Ento- |isbn=0-19-860613-3}}</ref> and the differing meanings of "Bryozoa" have caused much confusion.<ref>{{cite journal |last=Cuffey |first=R. J. |date=1969 |title=Bryozoa versus Ectoprocta – The Necessity for Precision |journal=Systematic Zoology |volume=18 |issue=2 |pages=250–251 |doi=10.2307/2412617 |jstor=2412617 }}</ref> ITIS treats the term "Bryozoa" as "invalid – junior synonym", in other words "Ectoprocta" is the longer-established name and ITIS recommends that "Bryozoa" should not be used to identify this phylum.<ref>{{cite web |url=https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=155469 |title=ITIS Standard Report Page: Bryozoa |publisher=Integrated Taxonomic Information System |access-date=2009-08-23}}</ref> -->

Until 2008 there were "inadequately known and misunderstood type species belonging to the Cyclostome Bryozoan family Oncousoeciidae."<ref>Taylor, Zaton 2008</ref> Modern research and experiments have been done using low-vacuum scanning electron microscopy of uncoated type material to critically examine and perhaps revise the taxonomy of three genera belonging to this family, including ''Oncousoecia'', ''Microeciella'', and ''Eurystrotos''. This method permits data to be obtained that would be difficult to recognize with an optical microscope. The valid type species of ''Oncousoecia'' was found to be ''Oncousoecia lobulata''. This interpretation stabilizes ''Oncousoecia'' by establishing a type species that corresponds to the general usage of the genus. Fellow Oncousoeciid ''Eurystrotos'' is now believed to be not conspecific with ''O. lobulata'', as previously suggested, but shows enough similarities to be considered a junior synonym of ''Oncousoecia''. ''Microeciella suborbicularus'' has also been recently distinguished from ''O. lobulata'' and ''O. dilatans'', using this modern method of low vacuum scanning, with which it has been inaccurately synonymized with in the past. A new genus has also been recently discovered called ''Junerossia'' in the family Stomachetosellidae, along with 10 relatively new species of bryozoa such as ''Alderina flaventa'', ''Corbulella extenuata'', ''Puellina septemcryptica'', ''Junerossia copiosa'', ''Calyptotheca kapaaensis'', ''Bryopesanser serratus'', ''Cribellopora souleorum'', ''Metacleidochasma verrucosa'', ''Disporella compta'', and ''Favosipora adunca''.<ref>{{cite journal |last1=Taylor |first1=Paul D |title=Taxonomy of the bryozoan genera Oncousoecia, Microeciella and Eurystrotos |journal=Journal of Natural History |date=October 2008 |volume= 42 |issue=39–40 |pages=2557–2574 |doi=10.1080/00222930802277640 |s2cid=84315311}}</ref>

=== Classification and diversity ===
Counts of formally described species range between 4,000 and 4,500.<ref>{{cite book |last=Chapman |first=A.D. |title=Numbers of Living Species in Australia and the World |publisher=Department of the Environment and Heritage, Australian Government |year=2006 |page=34 |isbn=978-0-642-56849-6 |url=http://www.environment.gov.au/biodiversity/abrs/publications/other/species-numbers/pubs/number-living-species-report.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.environment.gov.au/biodiversity/abrs/publications/other/species-numbers/pubs/number-living-species-report.pdf |archive-date=2022-10-09 |url-status=live |access-date=2009-08-07}}</ref> The Gymnolaemata and especially Cheilostomata have the greatest numbers of species, possibly because of their wide range of specialist zooids.<ref name="Doherty2001EctoproctaInAnderson" /> Under the [[Linnaean taxonomy|Linnaean system of classification]], which is still used as a convenient way to label groups of organisms,<ref name="RuppertFoxBarnesCladistics">{{cite book | author1=Ruppert, E.E. | author2=Fox, R.S. | author3=Barnes, R.D. | name-list-style=amp | title=Invertebrate Zoology | chapter=Introduction to Invertebrates | publisher=Brooks / Cole | edition=7 | isbn=978-0-03-025982-1 | year=2004 | pages=[https://archive.org/details/isbn_9780030259821/page/2 2–9] | chapter-url=https://archive.org/details/isbn_9780030259821/page/2 }}</ref> living members of the [[phylum]] Bryozoa are divided into:<ref name="RuppertFoxBarnesBryozoa" /><ref name="Doherty2001EctoproctaInAnderson" />

{| class="wikitable"
! [[Class (biology)|Class]] !! [[Phylactolaemata]] !! [[Stenolaemata]] !! colspan="2" | [[Gymnolaemata]]
|- align="center"
! [[Order (biology)|Order]] !! [[Plumatellida]]<ref>{{cite web |url=https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=156688 |title=ITIS Standard Report Page: Phylactolaemata |publisher=Integrated Taxonomic Information System |access-date=2009-08-12 |archive-date=18 January 2018 |archive-url=https://web.archive.org/web/20180118182014/https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=156688 |url-status=live }}</ref>!! [[Cyclostomatida]] !! [[Ctenostomatida]] !! [[Cheilostomata]]
|- align="center"
! Environments
| [[Freshwater]] || Marine || colspan="2" | Mostly marine
|- align="center"
! Lip-like epistome overhanging mouth
| Yes || colspan="3" | none
|- align="center"
! Colony shapes
| Gelatinous masses or tubular branching structures<ref name="MassardGeimer2008FreshwaterBryoDiversity">{{cite journal |last1=Massard |first1=J.A. |year=2008 |title=Global diversity of bryozoans (Bryozoa or Ectoprocta) in freshwater |journal=[[Hydrobiologia]] |volume=595 |pages=93–99 |doi=10.1007/s10750-007-9007-3 |last2=Geimer |first2=Gaby |issue=1 |bibcode=2008HyBio.595...93M |s2cid=13057599}}</ref> || colspan="2" | Erect or encrusting<ref name="FishFish1996StudentsGuide" /> || Erect, encrusting or free-living
|- align="center"
! Exoskeleton material
| Gelatinous or membranous; unmineralized || Mineralized || [[Chitin]], gelatinous or membranous; unmineralized || Mineralized
|- align="center"
! Operculum ("lid")
| none || none<ref name="FishFish1996StudentsGuide">{{cite book |last=Fish |first=J.D. |author2=Fish, S. |title=A student's guide to the seashore |year=1996 |edition=2 |pages=[https://archive.org/details/studentsguideto00fish/page/418 418–419] |chapter=Bryozoa |isbn=978-0-521-46819-0 |publisher=Cambridge University Press |location=Cambridge |chapter-url=https://archive.org/details/studentsguideto00fish/page/418}}</ref> (except in family [[Eleidae]])<ref>{{cite journal |last1=Jablonski |first1=D. |last2=Lidgard |first2=S. |last3=Taylor |first3=P.D. |year=1997 |title=Comparative Ecology of Bryozoan Radiations: Origin of novelties in cyclostomes and Cheilostomes |journal=[[PALAIOS]] |volume=12 |pages=505–523 |doi=10.2307/3515408 |jstor=3515408 |issue=6 |bibcode=1997Palai..12..505J}}</ref> || None in most species || Yes (except in genus ''[[Bugula]]'')
|- align="center"
! Shape of lophophore
| U-shaped appearance{{pb}}(except in [[genus]] ''[[Fredericella]]'', whose lophophore is circular) || colspan="3" | Circular
|- align="center"
! How lophophore extended
| Compressing the whole body wall || Compressing the membranous sac{{pb}}(separate inner layer of [[epithelium]] that lines the coelom) || Compressing the whole body wall || Pulling inwards of a flexible section of body wall, or making an internal sac expand.
|- align="center"
! Types of zooid
| Autozooids only || Limited heterozooids, mainly gonozooids<ref name="HaywardRyland1985Cyclostome">{{cite book |last=Hayward |first=P.J. |author2=Ryland, J.S. |title=Cyclostome bryozoans |publisher=Linnean Society of London |year=1985 |page=7 |chapter=Key to the higher taxa of marine Bryozoa |isbn=978-90-04-07697-6 |chapter-url=https://books.google.com/books?id=cAsVAAAAIAAJ&q=Stenolaemata+Cyclostomata+heterozooid&pg=PA7 |access-date=2009-08-09 |archive-date=8 March 2023 |archive-url=https://web.archive.org/web/20230308183237/https://books.google.com/books?id=cAsVAAAAIAAJ&q=Stenolaemata+Cyclostomata+heterozooid&pg=PA7 |url-status=live }}</ref> || [[Stolon]]s and spines as well as autozooids<ref name="HaywardRyland1985Cyclostome" /> || Full range of types
|}

=== Fossil record ===
[[File:OilShaleFossilsEstonia.jpg |thumb |Bryozoan fossils in an Upper [[Ordovician]] oil shale ([[kukersite]]), northern [[Estonia]].]]
{{stereo image
 |image = Arhimedes3d.jpg
 |caption = Fossilized skeleton of [[Archimedes (bryozoan)|Archimedes Bryozoan]]
 |width = 450
 |height = 200
}}
Fossils of about 15,000 bryozoan species have been found. Bryozoans are among the three dominant groups of Paleozoic fossils.<ref name="Bryozoan Evolution">{{cite news |last1=McKinney |last2=Frank K |last3=Jeremy |title=Bryozoan Evolution |publisher=Boston: Unwin & Hyman, 1989}}</ref> Bryozoans with calcitic skeletons were a major source of the carbonate minerals that make up limestones, and their fossils are incredibly common in marine sediments worldwide from the Ordovician onward. However, unlike corals and other colonial animals found in the fossil record, Bryozoan colonies did not reach large sizes.<ref name="Phylum Bryozoa">{{cite book |last1=Ernst |first1=Andrej |title=Phylum Bryozoa |date=2020 |pages=11–56 |chapter=2- Fossil record and evolution of Bryozoa}}</ref> Fossil bryozoan colonies are typically found highly fragmented and scattered; the preservation of complete zoaria is uncommon in the fossil record, and relatively little study has been devoted to reassembling fragmented zoaria.<ref>{{cite journal |last1=Jackson |first1=Patrick N. Wyse |last2=Key |first2=Marcus M. Key Jr. |title=Epizoan and endoskeletozoan distribution across reassembled ramose stenolaemate bryozoan zoaria from the Upper Ordovician (Katian) of the Cincinnati Arch region, USA |journal=Australasian Palaeontological Memoirs |date=2019 |volume=52 |pages=169–178}}</ref> The largest known fossil colonies are branching trepostome bryozoans from Ordovician rocks in the United States, reaching 66 centimeters in height.<ref name="Phylum Bryozoa"/>

The oldest species with a [[biomineralization|mineralized]] skeleton occurs in the Lower [[Ordovician]].<ref name="Taylor2013" /> It is likely that the first bryozoans appeared much earlier and were entirely soft-bodied, and the Ordovician fossils record the appearance of mineralized skeletons in this phylum.<ref name="FuchsObstSundberg2009ComprMolPhyloOfBryozoa" /> By the [[Arenigian]] stage of the Early Ordovician [[Period (geology)|period]],<ref name="RichFenton1997Bryozoans" /><ref>{{cite journal |last1=Torsvik |first1=T.H. |date=January 1991 |journal=Geology |volume=19 |issue=1 |pages=7–10 |doi=10.1130/0091-7613(1991)019<0007:COPOB>2.3.CO;2 |title=Cambrian-Ordovician paleogeography of Baltica |last2=Ryan |first2=Paul D. |last3=Trench |first3=Allan |last4=Harper |first4=David A.T. |author-link4 = David Harper (palaeontologist) |bibcode = 1991Geo....19....7T }}</ref> about {{ma|480}}, all the modern [[Order (biology)|orders]] of [[Stenolaemata|stenolaemates]] were present,<ref name="DewelWinstonMcKinney2001Deconstructing" /> and the [[Ctenostomatida|ctenostome]] order of [[Gymnolaemata|gymnolaemates]] had appeared by the Middle Ordovician, about {{ma|465}}. The Early Ordovician fossils may also represent forms that had already become significantly different from the original members of the phylum.<ref name="DewelWinstonMcKinney2001Deconstructing" /> Ctenostomes with phosphatized soft tissue are known from the Devonian.<ref name="Olempska2012">{{cite journal | last1 = Olempska | first1 = E. | doi = 10.4202/app.2011.0200 | title = Exceptional soft-tissue preservation in boring ctenostome bryozoans and associated "fungal" borings from the Early Devonian of Podolia, Ukraine | journal = Acta Palaeontologica Polonica | year = 2012 | volume=57 | issue = 4 | pages=925–940 | doi-access = free }}</ref> Other types of [[filter feeder]]s appeared around the same time, which suggests that some change made the environment more favorable for this lifestyle.<ref name="RichFenton1997Bryozoans" /> Fossils of [[Cheilostomata|cheilostomates]], an order of gymnolaemates with mineralized skeletons, first appear in the Mid [[Jurassic]], about {{ma|172}}, and these have been the most abundant and diverse bryozoans from the [[Cretaceous]] to the present.<ref name="RichFenton1997Bryozoans" /> Evidence compiled from the last 100&nbsp;million years show that cheilostomatids consistently grew over cyclostomatids in territorial struggles, which may help to explain how cheilostomatids replaced cyclostomatids as the dominant marine bryozoans.<ref>{{cite journal |last=McKinney |first=F.K. |year=1994 |title=One hundred million years of competitive interactions between bryozoan clades: asymmetrical but not escalating |journal=Biological Journal of the Linnean Society |volume=56 |issue=3 |pages=465–481 |doi=10.1111/j.1095-8312.1995.tb01105.x}}</ref> Marine fossils from the [[Paleozoic]] era, which ended {{ma |251}}, are mainly of erect forms, those from the [[Mesozoic]] are fairly equally divided by erect and encrusting forms, and more recent ones are predominantly encrusting.<ref>{{cite book |last=Wood |first=R. |title=Reef evolution |publisher=Oxford University Press |year=1999 |pages=235–237 |isbn=978-0-19-857784-3 |url=https://books.google.com/books?id=H_ah6Hzib4AC&q=bryozoa+distribution+range&pg=PA235 |access-date=2009-08-11 |archive-date=8 March 2023 |archive-url=https://web.archive.org/web/20230308183234/https://books.google.com/books?id=H_ah6Hzib4AC&q=bryozoa+distribution+range&pg=PA235 |url-status=live }}</ref> Fossils of the soft, freshwater [[Phylactolaemata|phylactolaemates]] are very rare,<ref name="RichFenton1997Bryozoans" /> appear in and after the Late Permian (which began about {{ma |260}}) and consist entirely of their durable statoblasts.<ref name="MassardGeimer2008FreshwaterBryoDiversity" /> There are no known fossils of freshwater members of other classes.<ref name="MassardGeimer2008FreshwaterBryoDiversity" />

=== Evolutionary family tree ===
[[File:OrdovicianEdrio.jpg |thumb |right |An Upper [[Ordovician]] cobble with the [[edrioasteroid]] ''Cystaster stellatus'' and the thin branching cyclostome bryozoan ''Corynotrypa''. Kope Formation, northern Kentucky, United States.]]
Scientists are divided about whether the Bryozoa (Ectoprocta) are a [[monophyletic]] group (whether they include all and only a single ancestor species and all its descendants), about what are the phylum's closest relatives in the family tree of animals, and even about whether they should be regarded as members of the [[protostome]]s or [[deuterostome]]s, the two major groups that account for all moderately complex animals.

Molecular phylogeny, which attempts to work out the evolutionary family tree of organisms by comparing their [[biochemistry]] and especially their [[gene]]s, has done much to clarify the relationships between the better-known [[invertebrate]] phyla.<ref name="Halanych2004AnimalPhylogeny" /> However, the shortage of genetic data about "minor phyla" such as bryozoans and [[Entoprocta|entoprocts]] has left their relationships to other groups unclear.<ref name="HausdorfHelmkampfMeyer2007Spiralian Phylogenomics">{{cite journal |last1=Hausdorf |first1=B. |year=2007 |title=Spiralian Phylogenomics Supports the Resurrection of Bryozoa Comprising Ectoprocta and Entoprocta |journal=Molecular Biology and Evolution |volume=24 |issue=12 |pages=2723–2729 |doi=10.1093/molbev/msm214 |pmid=17921486 |last2=Helmkampf |first2=M. |last3=Meyer |first3=A. |last4=Witek |first4=A. |last5=Herlyn |first5=H. |last6=Bruchhaus |first6=I. |last7=Hankeln |first7=T. |last8=Struck |first8=T.H. |last9=Lieb |first9=B. |doi-access=free}}</ref>

====Traditional view====
The traditional view is that the Bryozoa are a monophyletic group, in which the class [[Phylactolaemata]] is most closely related to [[Stenolaemata]] and [[Ctenostomatida]], the [[Class (biology)|classes]] that appear earliest in the fossil record.<ref name="WoodLore2005PhylactolaemateMolPhylo" /> However, in 2005 a [[molecular phylogeny]] study that focused on phylactolaemates concluded that these are more closely related to the phylum [[Phoronid]]a, and especially to the only phoronid species that is colonial, than they are to the other ectoproct classes. That implies that the Entoprocta are not monophyletic, as the Phoronida are a sub-group of ectoprocts but the standard definition of Entoprocta excludes the Phoronida.<ref name="WoodLore2005PhylactolaemateMolPhylo" />

[[File:Ropalonaria large 010213.jpg|thumb|''Ropalonaria venosa'', an etching [[trace fossil]] of a Late Ordovician ctenostome bryozoan on a strophomenid [[brachiopod]] valve; Cincinnatian of southeastern Indiana, United States.<ref>{{cite journal |last= Pohowsky |first=R.A. |year= 1978 |title=The boring ctenostomate bryozoa: taxonomy and paleobiology based on cavities in calcareous substrata |journal=Bulletins of American Paleontology |volume=73 |pages=192p}}</ref>]]
In 2009 another [[molecular phylogeny]] study, using a combination of genes from [[mitochondria]] and the [[cell nucleus]], concluded that Bryozoa is a [[monophyletic]] phylum, in other words includes all the descendants of a common ancestor that is itself a bryozoan. The analysis also concluded that the [[class (biology)|classes]] Phylactolaemata, [[Stenolaemata]] and [[Gymnolaemata]] are also monophyletic, but could not determine whether [[Stenolaemata]] are more closely related to [[Phylactolaemata]] or [[Gymnolaemata]]. The Gymnolaemata are traditionally divided into the soft-bodied [[Ctenostomatida]] and [[biomineralization|mineralized]] Cheilostomata, but the 2009 analysis considered it more likely that neither of these [[order (biology)|orders]] is monophyletic and that mineralized [[skeleton]]s probably evolved more than once within the early Gymnolaemata.<ref name="FuchsObstSundberg2009ComprMolPhyloOfBryozoa">{{cite journal |last1=Fuchs |first1=J. |date=July 2009 |title=The first comprehensive molecular phylogeny of Bryozoa (Ectoprocta) based on combined analyses of nuclear and mitochondrial genes |journal=Molecular Phylogenetics and Evolution |volume=52 |issue=1 |pages=225–233 |doi=10.1016/j.ympev.2009.01.021 |pmid=19475710 |last2=Obst |first2=M. |last3=Sundberg |first3=P|bibcode=2009MolPE..52..225F }}</ref>

Bryozoans' relationships with other phyla are uncertain and controversial. Traditional phylogeny, based on [[anatomy]] and on the development of the adult forms from [[embryo]]s, has produced no enduring consensus about the position of ectoprocts.<ref name="Nielsen2002PhyloPosOfEntoproctaEctoproctaPhoronidaBrachiopoda" /> Attempts to reconstruct the family tree of animals have largely ignored ectoprocts and other "minor phyla", which have received little scientific study because they are generally tiny, have relatively simple body plans, and have little impact on human economies – despite the fact that the "minor phyla" include most of the variety in the evolutionary history of animals.<ref>{{cite journal |last1=Garey |first1=J.R. |year=1998 |title=The Essential Role of "Minor" Phyla in Molecular Studies of Animal Evolution |journal=American Zoologist |volume=38 |issue=6 |pages=907–917 |doi=10.1093/icb/38.6.907 |last2=Schmidt-Rhaesa |first2=Andreas |doi-access=free}}</ref>

In the opinion of Ruth Dewel, Judith Winston, and Frank McKinney, "Our standard interpretation of bryozoan [[morphology (biology)|morphology]] and [[embryology]] is a construct resulting from over 100 years of attempts to synthesize a single framework for all invertebrates," and takes little account of some peculiar features of ectoprocts.<ref name="DewelWinstonMcKinney2001Deconstructing" />

[[File:Phaenopora superba Silurian Brassfield.jpeg|thumb|''Phaenopora superba'', a ptilodictyine bryozoan from the Silurian of [[Ohio]], United States]]
[[File:Sucoretepora.jpg|thumb|The flat, branching bryozoan ''Sulcoretepora'', from the Middle Devonian of [[Wisconsin]], United States]]

In ectoprocts, all of the larva's internal organs are destroyed during the metamorphosis to the adult form and the adult's organs are built from the larva's [[Epidermis (skin)|epidermis]] and [[mesoderm]], while in other [[bilateria]]ns some organs including the gut are built from [[endoderm]]. In most bilaterian embryos the blastopore, a dent in the outer wall, deepens to become the larva's gut, but in ectoprocts the blastopore disappears and a new dent becomes the point from which the gut grows. The ectoproct coelom is formed by neither of the processes used by other bilaterians, [[enterocoely]], in which pouches that form on the wall of the gut become separate cavities, nor [[schizocoely]], in which the tissue between the gut and the body wall splits, forming paired cavities.<ref name="DewelWinstonMcKinney2001Deconstructing">{{cite book |last=Dewel |first=R.A. |author2=Winston, J.E. |author3=McKinney, F.J. |others=M.E. |title=Bryozoan studies 2001: proceedings of the Twelfth International Bryozoology Conference |editor=Wyse Jacksdon, P.E. |editor2=Buttler, C.E. |editor3=Spencer Jones, M.E. |publisher=Swets and Zeitlinger |location=Lisse |year=2002 |pages=93–96 |chapter=Deconstructing byozoans: origin and consequences of a unique body plan |isbn=978-90-5809-388-2 |chapter-url=https://books.google.com/books?id=4-jlUfCMlQkC&q=ectoprocta%20bryozoa%20phylogeny&pg=PA93 |access-date=2009-08-13 |archive-date=8 March 2023 |archive-url=https://web.archive.org/web/20230308183244/https://books.google.com/books?id=4-jlUfCMlQkC&q=ectoprocta%20bryozoa%20phylogeny&pg=PA93 |url-status=live }}</ref>

====Entoprocts====

When entoprocts were discovered in the 19th century, they and bryozoans (ectoprocts) were regarded as classes within the phylum Bryozoa, because both groups were [[Sessility (zoology)|sessile]] animals that [[filter feeder|filter-fed]] by means of a crown of tentacles that bore [[cilia]].

From 1869 onwards increasing awareness of differences, including the position of the entoproct [[anus]] inside the feeding structure and the difference in the early [[Cleavage (embryo)|pattern of division]] of cells in their [[embryo]]s, caused scientists to regard the two groups as separate phyla,<ref name="HausdorfHelmkampfMeyer2007Spiralian Phylogenomics" /> and "Bryozoa" became just an alternative name for ectoprocts, in which the anus is outside the feeding organ.<ref name="Halanych2004AnimalPhylogeny" /> A series of molecular phylogeny studies from 1996 to 2006 have also concluded that bryozoans (ectoprocts) and entoprocts are not sister groups.<ref name="HausdorfHelmkampfMeyer2007Spiralian Phylogenomics" />

However, two well-known zoologists, Claus Nielsen and [[Thomas Cavalier-Smith]], maintain on anatomical and developmental grounds that bryozoans and entoprocts are member of the same phylum, Bryozoa. A molecular phylogeny study in 2007 also supported this old idea, while its conclusions about other phyla agreed with those of several other analyses.<ref name="HausdorfHelmkampfMeyer2007Spiralian Phylogenomics" />

====Grouping into the Lophophorata====

By 1891 bryozoans (ectoprocts) were grouped with [[phoronid]]s in a super-phylum called "Tentaculata". In the 1970s comparisons between phoronid larvae and the [[cyphonautes]] larva of some gymnolaete bryozoans produced suggestions that the bryozoans, most of which are colonial, evolved from a semi-colonial species of phoronid.<ref name="Nielsen2001AnimalEvoPhylumEctoprocta">{{cite book |last=Nielsen |first=C. |title=Animal evolution: interrelationships of the living phyla |publisher=Oxford University Press |year=2001 |edition=2 |pages=244–264 |chapter=Phylum Ectoprocta |isbn=978-0-19-850681-2 |chapter-url=https://books.google.com/books?id=UmCg6c0HkqMC&q=ectoprocta%20bryozoa%20phylogeny&pg=PA257 |access-date=2009-08-14 |archive-date=8 March 2023 |archive-url=https://web.archive.org/web/20230308183241/https://books.google.com/books?id=UmCg6c0HkqMC&q=ectoprocta%20bryozoa%20phylogeny&pg=PA257 |url-status=live }}</ref> [[Brachiopod]]s were also assigned to the "Tentaculata", which were renamed [[Lophophorata]] as they all use a [[lophophore]] for filter feeding.<ref name="Halanych2004AnimalPhylogeny" />

The majority of scientists accept this,<ref name="Halanych2004AnimalPhylogeny" /> but Claus Nielsen thinks these similarities are superficial.<ref name="Nielsen2002PhyloPosOfEntoproctaEctoproctaPhoronidaBrachiopoda">{{cite journal |last=Nielsen |first=C. |date=July 2002 |title=The Phylogenetic Position of Entoprocta, Ectoprocta, Phoronida, and Brachiopoda |journal=Integrative and Comparative Biology |volume=42 |issue=3 |pages=685–691 |doi=10.1093/icb/42.3.685 |pmid=21708765 |doi-access=free }}</ref> The Lophophorata are usually defined as animals with a lophophore, a three-part coelom and a U-shaped gut.<ref name="Nielsen2001AnimalEvoPhylumEctoprocta" /> In Nielsen's opinion, phoronids' and brachiopods' lophophores are more like those of [[pterobranch]]s,<ref name="Nielsen2002PhyloPosOfEntoproctaEctoproctaPhoronidaBrachiopoda" /> which are members of the phylum [[Hemichordata]].<ref>{{cite web |url=http://www.ucmp.berkeley.edu/chordata/hemichordata.html |access-date=2008-09-22 |title=Introduction to the Hemichordata |publisher=University of California Museum of Paleontology |archive-url=https://web.archive.org/web/20190201080336/http://www.ucmp.berkeley.edu/chordata/hemichordata.html |archive-date=1 February 2019 |url-status=dead }}</ref> Bryozoan's tentacles bear cells with multiple [[cilia]], while the corresponding cells of phoronids', brachiopods' and pterobranchs' lophophores have one cilium per cell; and bryozoan tentacles have no hemal canal ("blood vessel"), which those of the other three phyla have.<ref name="Nielsen2002PhyloPosOfEntoproctaEctoproctaPhoronidaBrachiopoda" />

If the grouping of bryozoans with phoronids and brachiopods into Lophophorata is correct, the next issue is whether the Lophophorata are [[protostome]]s, along with most invertebrate phyla, or [[deuterostome]]s, along with [[chordate]]s, [[hemichordate]]s and [[echinoderm]]s.

The traditional view was that lophophorates were a mix of protostome and deuterostome features. Research from the 1970s onwards suggested they were deuterostomes, because of some features that were thought characteristic of deuterostomes: a three-part coelom; radial rather than spiral cleavage in the development of the embryo;<ref name="Halanych2004AnimalPhylogeny" /> and formation of the coelom by [[enterocoely]].<ref name="Nielsen2002PhyloPosOfEntoproctaEctoproctaPhoronidaBrachiopoda" /> However the coelom of ectoproct larvae shows no sign of division into three sections,<ref name="Nielsen2001AnimalEvoPhylumEctoprocta" /> and that of adult ectoprocts is different from that of other [[coelomate]] phyla as it is built anew from epidermis and mesoderm after metamorphosis has destroyed the larval coelom.<ref name="DewelWinstonMcKinney2001Deconstructing" />

====Lophophorate molecular phylogenetics====

Molecular phylogeny analyses from 1995 onwards, using a variety of biochemical evidence and analytical techniques, placed the lophophorates as protostomes and closely related to [[annelid]]s and [[mollusc]]s in a super-phylum called [[Lophotrochozoa]].<ref name="Halanych2004AnimalPhylogeny" /><ref name="HelmkampfBruchhausHausdorf2008PhylogenOfLophophorates">{{cite journal |last1=Helmkampf |first1=M. |year=2008 |title=Phylogenomic analyses of lophophorates (brachiopods, phoronids and bryozoans) confirm the Lophotrochozoa concept |journal=Proceedings of the Royal Society B: Biological Sciences |volume=275 |pages=1927–1933 |doi=10.1098/rspb.2008.0372 |last2=Bruchhaus |first2=Iris |last3=Hausdorf |first3=Bernhard |pmid=18495619 |issue=1645 |pmc=2593926}}</ref> "Total evidence" analyses, which used both morphological features and a relatively small set of genes, came to various conclusions, mostly favoring a close relationship between lophophorates and Lophotrochozoa.<ref name="HelmkampfBruchhausHausdorf2008PhylogenOfLophophorates" /> A study in 2008, using a larger set of genes, concluded that the lophophorates were closer to the Lophotrochozoa than to deuterostomes, but also that the lophophorates were not monophyletic. Instead, it concluded that brachiopods and phoronids formed a monophyletic group, but bryozoans (ectoprocts) were closest to entoprocts, supporting the original definition of "Bryozoa".<ref name="HelmkampfBruchhausHausdorf2008PhylogenOfLophophorates" />

They are the only major phylum of exclusively clonal animals, composed of modular units known as zooids. Because they thrive in colonies, colonial growth allows them to develop unrestricted variations in form. Despite this, only a small number of basic growth forms have been found and have commonly reappeared throughout the history of the bryozoa.<ref name="Bryozoan Evolution" />

{{clade
|label1=[[Lophotrochozoa]]
|1={{clade
   |1=[[Cycliophora]] <span style="{{MirrorH}}">[[File:CYC-000044 hab Symbion Z5v2v5N.png|70px]]</span>
   |2=[[Annelida]] [[File:Polychaeta (no) 2.jpg|70px]]
   |3={{clade
      |1=[[Mollusca]] <span style="{{MirrorH}}">[[File:Grapevinesnail 01a.jpg|65px]]</span>
      |label2=<!--[[Kryptotrochozoa]]-->
      |2={{clade
         |label1=[[Lophophorata]]
         |1={{clade
            |label1=[[Brachiozoa]]
            |1={{clade
               |1=[[Brachiopoda]] [[File:LingulaanatinaAA_(cropped).JPG|60px]]
               |2=[[Phoronida]] <span style="{{MirrorH}}">[[File:Phoronopsis harmeri IZ 1643662.png|70px]]</span>
               }}
            |label2='''Bryozoa''' [[sensu lato|''s.l.'']]
            |2={{clade
               |1='''[[Entoprocta]]''' [[File:Barentsia laxa 1498941 (no background).png|80px]]
               |2='''[[Ectoprocta]]''' [[File:Bugulina flabellata 272067784.png|70px]]
               }}
            }}
         }}
      }}
   }}
}}

====Ectoproct molecular phylogenetics====
The phylogenetic position of the ectoproct bryozoans remains uncertain, but it remains certain that they belong to the Protostomia and more specifically to the Lophotrochozoa. This implies that the ectoproct larva is a trochophore with the corona being a homologue of the prototroch; this is supported from the similarity between the coronate larvae and the Type 1 pericalymma larvae of some molluscs and sipunculans, where the prototroch zone is expanded to cover the hyposphere.<ref>{{cite journal |last1=Nielsen |first1=C. |last2=Worsaae |first2=K. |title=Structure and occurrence of cyphonautes larvae (Bryozoa, Ectoprocta) |journal=Journal of Morphology |date=September 2010 |volume=271 |issue=9 |pages=1094–1109 |doi=10.1002/jmor.10856 |pmid=20730922 |s2cid=11453241}}</ref>

A study of the mitochondrial DNA sequence suggests that the Bryozoa may be related to the [[Chaetognatha]].<ref name=Shen2012>{{cite journal |author1=Shen, X. |author2=Tian, M. |author3=Meng, X. |author4=Liu, H. |author5=Cheng, H. |author6=Zhu, C. |author7=Zhao, F. |title=Complete mitochondrial genome of ''Membranipora grandicella'' (Bryozoa: Cheilostomatida) determined with next-generation sequencing: The first representative of the suborder Malacostegina |journal=Comparative Biochemistry and Physiology Part D: Genomics and Proteomics |date=September 2012 |volume=7 |issue=3 |pages=248–253 |doi=10.1016/j.cbd.2012.03.003 |pmid=22503287}}</ref>