Editing Demosponge (section)

== Classification and systematics ==

The Demospongiae have an ancient history. The first demosponges may have appeared during the [[Precambrian]] deposits at the end of the [[Cryogenian]] "Snowball Earth" period. Their presence has been indirectly detected by fossilized steroids, called [[sterane]]s, hydrocarbon markers characteristic of the cell membranes of the sponges, rather than from direct fossils of the sponges themselves. They represent a continuous [[chemical fossil]] record of demosponges through the end of the [[Neoproterozoic]].<ref name=Love09/> The earliest Demospongiae fossil was discovered in the lower [[Cambrian]] (Series 2, Stage 3; approximately 515 Ma) of the [[Sirius Passet]] Biota of North Greenland:<ref name="Botting2015">{{cite journal |author1=Botting J.P. |author2=Cárdenas P. |author3=Peel J.S. | date = January 2015 | title = A crown-group demosponge from the early Cambrian Sirius Passet Biota, North Greenland | journal = Palaeontology | volume = 58 | issue = 1| pages = 35–43 | doi = 10.1111/pala.12133 | doi-access = free |bibcode=2015Palgy..58...35B }}</ref> this single specimen had a [[spicule (sponge)|spicule]] assemblage similar to that found in the subclass [[Heteroscleromorpha]]. The earliest sponge-bearing [[reef]]s date to the Early Cambrian (they are the earliest known reef structure built by animals), exemplified by a small bioherm constructed by [[archaeocyathid]]s and calcified microbes at the start of the [[Tommotian|Tommotian stage]] about 530 Ma, found in southeast Siberia.<ref>{{cite journal |author1=Riding Robert |author2=Andrey Yu. Zhuravlev | year = 1995 | title = Structure and 5 thousand years diversity of oldest sponge-microbe reefs: Lower Cambrian, Aldan River, Siberia | journal = Geology | volume = 23 | issue = 7| pages = 649–52 | doi = 10.1130/0091-7613(1995)023<0649:SADOOS>2.3.CO;2 }}</ref> A major radiation occurred in the Lower [[Cambrian]] and further major radiations in the [[Ordovician]] possibly from the middle Cambrian.<ref>{{cite book |first=R.M. |last=Finks |chapter=The evolution and ecologic history of sponges during Palaeozoic times |editor-first=W.G. |editor-last=Fry |title=Biology of the porifera |publisher=Academic Press |series=Symposium of the Zoological Society of London |volume=25 |date=1970 |isbn=0-12-613325-5 |oclc=1409104310 |pages=3–22 }}</ref>

The [[Systema Porifera]] (2002) book (2 volumes) was the result of a collaboration of 45 researchers from 17 countries led by editors J. N. A. Hooper and R. W. M. van Soest.<ref>{{cite book |last1=Hooper |first1=J.N.A. |last2=Van Soest |first2=R.W.M. |chapter=Class Demospongiae Sollas, 1885 |chapter-url=https://link.springer.com/chapter/10.1007/978-1-4615-0747-5_3 |editor-last=Hooper |editor-first=J.N.A. |editor2-last=Van Soest |editor2-first=R.W.M. |editor3-last=Willenz |editor3-first=P. |title=Systema Porifera. A guide to the classification of sponges |publisher=Springer |date=2002 |isbn=978-1-4615-0747-5 |pages=15–51 |doi=10.1007/978-1-4615-0747-5_3}}</ref> This milestone publication provided an updated comprehensive overview of sponge [[systematics]], the largest revision of this group (from genera, subfamilies, families, suborders, orders and class) since the start of spongiology in the mid-19th century. In this large revision, the extant Demospongiae were organized into 14 orders that encompassed 88 families and 500 genera. Hooper and van Soest (2002) gave the following classification of demosponges into orders:

* Subclass '''[[Homoscleromorpha]]''' <small>Bergquist, 1978</small>
** [[Homosclerophorida]] <small>Dendy, 1905</small>
* Subclass '''[[Tetractinomorpha]]'''
** [[Astrophorida]] <small>Sollas, 1888</small>
** [[Chondrosida]] <small>Boury-Esnault & Lopès, 1985</small>
** [[Hadromerida]] <small>Topsent, 1894</small>
** [[Lithistida]] <small>Sollas, 1888</small>
** [[Spirophorida]] <small>Bergquist & Hogg, 1969</small>
* Subclass '''[[Ceractinomorpha]]''' <small>Lévi, 1953</small>
** [[Agelasida]] <small>Verrill, 1907</small>
** [[Dendroceratida]] <small>Minchin, 1900</small>
** [[Dictyoceratida]] <small>Minchin, 1900</small>
** [[Halichondrida]] <small>Gray, 1867</small>
** [[Halisarcida]] <small>Bergquist, 1996</small>
** [[Haplosclerida]] <small>Topsent, 1928</small>
** [[Poecilosclerida]] <small>Topsent, 1928</small><!-- Zoological Journal of the Linnean Society, 2006, 148, 553–584. -->
** [[Verongiida]] <small>Bergquist, 1978</small>
** [[Verticillitida]] <small>Termier & Termier, 1977</small>

However, molecular and morphological evidence show that the [[Homoscleromorpha]] do not belong in this class. The [[Homoscleromorpha]] was therefore officially taken out of the Demospongiae in 2012, and became the fourth class of phylum Porifera.<ref>{{cite journal |author1=Gazave E. |author2=Lapébie P. |author3=Ereskovsky A. |author4=Vacelet J. |author5=Renard E. |author6=Cárdenas P. |author7=Borchiellini C. | year = 2012 | title = No longer Demospongiae: Homoscleromorpha formal nomination as a fourth class of Porifera | journal = Hydrobiologia | volume = 687 |issue=1 | pages = 3–10 | doi = 10.1007/s10750-011-0842-x |bibcode=2012HyBio.687....3G |s2cid=14468684 |url=https://hal.archives-ouvertes.fr/hal-01456632/file/Gazave%20et_2012-%20class.pdf }}</ref>
[[File:Nevadacoelia wistae.jpg|thumb|''[[Nevadacoelia|Nevadacoelia wistae]]'', a fossil [[Anthaspidellidae|anthaspidellid]] demosponge from the early [[Ordovician]] of [[Nevada]].]]
Morrow & Cárdenas (2015)<ref>{{cite journal |author1=Morrow Christine |author2=Cárdenas Paco | year = 2015 | title = Proposal for a revised classification of the Demospongiae (Porifera) | journal = Frontiers in Zoology | volume = 12 | pages = 1–27 | doi =  10.1186/s12983-015-0099-8|pmid=25901176 |pmc=4404696 |doi-access=free }}</ref> propose a revision of the Demospongiae higher taxa classification, essentially based on molecular data of the last ten years. Some demosponge subclasses and orders are actually [[polyphyletic]] or should be included in other orders, so that Morrow and Cárdenas (2015) officially propose to abandon certain names: these are the [[Ceractinomorpha]], [[Tetractinomorpha]], [[Halisarcida]], [[Verticillitida]], [[Lithistida]], [[Halichondrida]] and [[Hadromerida]]. Instead, they recommend the use of three subclasses: [[Verongimorpha]], [[Keratosa]] and [[Heteroscleromorpha]]. They retain seven ([[Agelasida]], [[Chondrosiida]], [[Dendroceratida]], [[Dictyoceratida]], [[Haplosclerida]], [[Poecilosclerida]], [[Verongida|Verongiida]]) of the 13 orders from Systema Porifera. They recommend to resurrect or upgrade six order names ([[Axinellida]], [[Merliida]], [[Spongillida]], [[Sphaerocladina]], [[Suberitida]], [[Tetractinellida]]). Finally, they create seven new orders ([[Bubarida]], [[Desmacellida]], [[Polymastiida]], [[Scopalinida]], [[Clionaida]], [[Tethyida]], [[Trachycladida]]). These added to the recently created orders ([[Biemnida]] and [[Chondrillida]]) make a total of 22 orders in the revised classification. These changes are now implemented in the World Porifera Database<ref>{{cite web|url=http://www.marinespecies.org/porifera/|title=World Porifera Database}}</ref> part of the World Register of Marine Species.

* Subclass '''[[Heteroscleromorpha]]''' <small>Cárdenas, Pérez, Boury-Esnault, 2012</small>
** order [[Agelasida]] <small>Verrill, 1907</small>
** order [[Axinellida]] <small>Lévi, 1953</small>
** order [[Biemnida]] <small>Morrow et al., 2013</small>
** order [[Bubarida]] <small>Morrow & Cárdenas, 2015</small>
** order [[Clionaida]] <small>Morrow & Cárdenas, 2015</small>
** order [[Desmacellida]] <small>Morrow & Cárdenas, 2015</small>
** order [[Haplosclerida]] <small>Topsent, 1928</small>
** order [[Merliida]] <small>Vacelet, 1979</small>
** order [[Poecilosclerida]] <small>Topsent, 1928</small>
** order [[Polymastiida]] <small>Morrow & Cárdenas, 2015</small>
** order [[Scopalinida]] <small>Morrow & Cárdenas, 2015</small>
** order [[Sphaerocladina]] <small>Schrammen, 1924</small>
** order [[Spongillida]] <small>Manconi & Pronzato, 2002</small>
** order [[Suberitida]] <small>Chombard & Boury-Esnault, 1999</small>
** order [[Tethyida]] <small>Morrow & Cárdenas, 2015</small>
** order [[Tetractinellida]] <small>Marshall, 1876</small>
** order [[Trachycladida]] <small>Morrow & Cárdenas, 2015</small>
** Heteroscleromorpha incertae sedis
* Subclass '''[[Verongimorpha]]''' <small>Erpenbeck et al., 2012</small>
** order [[Chondrillida]] <small>Redmond et al., 2013</small>
** order [[Chondrosiida]] <small>Boury-Esnault et Lopès, 1985</small>
** order [[Verongida|Verongiida]] <small>Bergquist, 1978</small>
* Subclass '''[[Keratosa]]''' <small>Grant, 1861</small>
** order [[Dendroceratida]] <small>Minchin, 1900</small>
** order [[Dictyoceratida]] <small>Minchin, 1900</small>

=== Sclerosponges ===
Sclerosponges were first proposed as a class of sponges, '''Sclerospongiae''', in 1970 by Hartman and Goreau.<ref>{{cite book |last1=Hartman |first1=W.D. |last2=Goreau |first2=T.F. |chapter=Jamaican coralline sponges: Their morphology, ecology and fossil relatives |editor-first=W.G. |editor-last=Fry |title=Biology of the porifera |publisher=Academic Press |series=Symposium of the Zoological Society of London |volume=25 |date=1970 |isbn=0-12-613325-5 |oclc=1409104310 |pages=205–243 }} (Cited by {{cite web |url=http://mgg.rsmas.miami.edu/groups/sil/work1.htm |date=21-23 March 1998 |title=Notes of the ''Sclerosponge Workshop'' |publisher=University of Miami |department=Stable Isotope Laboratory, Rosenstiel School of Marine and Atmospheric Science |location=Miami, FL |access-date=2018-12-19 |df=dmy-all |archive-date=2018-08-18 |archive-url=https://web.archive.org/web/20180818135926/http://mgg.rsmas.miami.edu/groups/sil/work1.htm |url-status=dead }})</ref> However, it was later found by Vacelet that sclerosponges occur in different classes of [[Porifera]].<ref>{{cite conference |first=J. |last=Vacelet |title=Coralline sponges and the evolution of the Porifera |book-title=The origins and relationships of lower invertebrates : Proceedings of an International symposium held in London, September 1983 |series=Systematics Association |volume=28 |publisher=Clarendon Press |date=1985 |isbn=0-19-857181-X |oclc=220503346 |pages=1–13 }}</ref> That means that sclerosponges are not a closely related ([[Taxonomy (biology)|taxonomic]]) group of sponges and are considered to be a polyphyletic grouping and contained within the Demospongiae. Like [[bat]]s and [[bird]]s that independently developed the ability to fly, different sponges developed the ability to build a calcareous skeleton independently and at different times in [[Geological history of Earth|Earth's history]]. Fossil sclerosponges are already known from the [[Cambrian]] period.<ref>{{cite journal |first=J. |last=Reitner |title=Coralline Spongien — Der Versuch einer phylogenetisch-taxonomischen Analyse |journal=Berliner geowissenschaftliche Abhandlungen. Reihe e, Paläobiologie |volume=1 |date=1992 |doi=10.23689/fidgeo-5876 |url=https://e-docs.geo-leo.de/handle/11858/11466}}<!-- Yes, the very first paper to appear in this journal! See http://userpage.fu-berlin.de/~palaeont/JOURNAL.HTM --></ref>

=== Chaetetids ===
<!-- [[Chaetetes]] anchors to this section -->
Chaetetids, more formally called "chaetetid hyper-calcified demosponges" (West, 2011), are common calcareous [[fossils]] composed of fused tubules. They were previously classified as extinct [[corals]], [[bryozoans]], [[algae]], [[stromatoporoidea|stromatoporoids]] and [[sclerosponges]]. The chaetetid skeleton has now been shown to be of polyphyletic origin and with little systematic value. Extant chaetetids are also described. This skeleton is now known from three demosponge orders (Hadromerida, Poecilosclerida, and Agelasida). Fossil chaetetid hyper-calcified demosponges can only be classified with information on their spicule forms and the original mineralogy of their skeletons (West, 2011).

<gallery widths="200px" heights="170px">
File:Chaetetid Bird Spring Upper Carboniferous Nevada.jpg|Fossil chaetetid from the [[Bird Spring Formation]] ([[Upper Carboniferous]]) of southern [[Nevada]].
File: Chaetetid Bird Spring cross-section Upper Carboniferous Nevada.jpg|Cross-section of a fossil chaetetid (Bird Spring Formation, Upper Carboniferous, Nevada.
</gallery>