Editing Bryozoa (section)

====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>