Editing Archaeocyatha (section)

==Taxonomy==
[[File:Antarcticocyathus webberi.jpg|thumb|Restoration of ''Antarcticocyathus webberi'']]Their [[phylogenetic]] affiliation has been subject to changing interpretations, yet the consensus is growing that the archaeocyath was indeed a kind of sponge,<ref name="Rowland2001ArchaeocyathaPhylogeneticInterpretations">Scuba divers have discovered living [[calcium carbonate|calcareous]] sponges, including one species that -- like the archaeocyathans -- is without [[spicule (sponge)|spicule]]s, thus morphologically similar to the archaeocyaths. {{cite journal
 |author=Rowland, S.M. 
 |title=Archaeocyatha: A history of phylogenetic interpretation 
 |journal=Journal of Paleontology 
 |volume=75 
 |pages=1065–1078 
 |doi=10.1666/0022-3360(2001)075<1065:AAHOPI>2.0.CO;2 
 |year=2001 
 |issue=6 
}}</ref> thus sometimes called a pleosponge.  But some [[invertebrate]] [[paleontologist]]s have placed them in an extinct, separate [[phylum (biology)|phylum]], known appropriately as the Archaeocyatha.<ref>Debrenne, F. and J. Vacelet. 1984. "Archaeocyatha: Is the sponge model consistent with their structural organization?" in ''Palaeontographica Americana'', '''54''':pp358-369.</ref>  However, one [[cladistic analysis]]<ref>J. Reitner. 1990. "Polyphyletic origin of the 'Sphinctozoans{{'"}}, in Rutzler, K. (ed.), ''New Perspectives in Sponge Biology: Proceedings of the Third International Conference on the Biology of Sponges'' (Woods Hole) pp. 33–42. Smithsonian Institution Press, Washington, DC.</ref> suggests that Archaeocyatha is a [[clade]] nested within the [[phylum]] [[Porifera]] (better known as the true sponges).

True archaeocyathans coexisted with other enigmatic sponge-like animals. [[Radiocyatha]] and [[Cribricyatha]] were two diverse Cambrian classes comparable to Archaeocyatha, alongside genera such as ''[[Boyarinovicyathus]]'', ''[[Proarchaeocyathus]]'', ''[[Acanthinocyathus]]'', and ''[[Osadchiites]]''.<ref name=":1">''Treatise on Invertebrate Paleontology'' Part E, Revised. Porifera, Volumes 4 & 5: Hypercalcified Porifera, Paleozoic Stromatoporoidea & Archaeocyatha, liii + 1223 p., 665 figs., 2015, available [https://journals.ku.edu/InvertebratePaleo/issue/view/538 here]. {{ISBN|978-0-9903621-2-8}}.</ref>

The [[clade]] Archaeocyatha have traditionally been divided into Regulares and Irregulares (Rowland, 2001):

* [[Hetairacyathida]] ([[incertae sedis]])
* [[Regulares (Archaeocyatha)|Regulares]]
** [[Monocyathida]]
** [[Capsulocyathida]]
** [[Ajacicyathida]]
* [[Irregulares]]
** [[Thalassocyathida]]
** [[Archaeocyathida]]
** [[Kazakhstanicyathida]]

However, Okulitch (1955), who at the time regarded the archaeocyathans as outside of Porifera, divided the phylum in three classes:

*Phylum Archaeocyatha <small>Vologdin, 1937</small>
**Class [[Monocyathea]] <small>Okulitch, 1943</small>
**Class [[Archaeocyathea]] <small>Okulitch, 1943</small>
**Class [[Anthocyathea]] <small>Okulitch, 1943</small>