Archaeocyatha

Archaeocyatha Temporal range: Tommotian - Mid Cambrian PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Porifera
Clade:	†Archaeocyatha Vologdin, 1937
Synonyms
Cyathospongia Okulitch, 1935 Pleospongia Okulitch, 1935

Archaeocyatha (

The remains of Archaeocyatha are mostly preserved as carbonate structures in a limestone matrix. This means that the fossils cannot be chemically or mechanically isolated, save for some specimens that have already eroded out of their matrices, and their morphology has to be determined from thin cuts of the stone in which they were preserved.

Geological history

Today, the archaeocyathan families are recognizable by small but consistent differences in their

The archaeocyathids were important reef-builders in the early to middle Cambrian, with reefs (and indeed any accumulation of carbonates) becoming very rare after the group's extinction until the diversification of new taxa of coral reef-builders in the Ordovician.^[5]

Antarcticocyathus was considered the only late Cambrian archaeocyath, but its reinterpretation as a lithisid sponge^[6] means that there are now no archaeocyaths post the mid-Cambrian.

Morphology

substrate by a holdfast

. The body presumably occupied the space between the inner and outer shells (the intervallum).

Ecology

See also: Sponge reef

Flow tank experiments suggest that archaeocyathan

extant sponges, by drawing water through the pores, removing nutrients, and expelling spent water and wastes through the pores into the central space.^{[citation needed}

]

The size of the pores places a limit on the size of plankton that archaeocyaths could have consumed; different species had different sized pores, the largest large enough to conceivably consume mesozooplankton, possibly giving rise to different ecological niches within a single reef.[7]

Distribution

Poleta formation

, eastern California

The archaeocyathans inhabited coastal areas of shallow seas. Their widespread distribution over almost the entire Cambrian world, as well as the

planktonic larval

stage that enabled their wide spread.

Taxonomy

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.^[11]

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

• Hetairacyathida (incertae sedis
  )
• 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 Vologdin, 1937
  • Class Monocyathea Okulitch, 1943
  • Class Archaeocyathea Okulitch, 1943
  • Class Anthocyathea Okulitch, 1943

Notes

1. ^ Archaeocyathid reef structures ("bioherms"), although not as massive as later coral reefs, might have been as deep as ten meters (Emiliani 1992:451).
2. S2CID 128842533
   .
3. Georgia Perimeter College. Archived from the original
   on 20 July 2011. Retrieved 6 July 2010.
4. ^ The last-recorded archaeocyathan is a single species from the late (upper) Cambrian of Antarctica.
5. doi:10.1016/j.palaeo.2010.08.001
   .
6. S2CID 254628199
   .
7. S2CID 208555519
   .
8. doi:10.1666/0022-3360(2001)075<1065:AAHOPI>2.0.CO;2
   .
9. ^ Debrenne, F. and J. Vacelet. 1984. "Archaeocyatha: Is the sponge model consistent with their structural organization?" in Palaeontographica Americana, 54:pp358-369.
10. ^ 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.
11. ISBN 978-0-9903621-2-8
    .

References

• ISBN 0-521-40949-7
  ), p 451
• Okulitch, V. J., 1955: Part E – Archaeocyatha and Porifera. Archaeocyatha, E1-E20 in Moore, R. C., (ed.) 1955: Treatise on Invertebrate Paleontology. Geological Society of America & University of Kansas Press, Lawrence, Kansas, 1955, xviii-E122.

External links

• knowledge base and interactive key for identification of archaeocyathan genera: http://www.infosyslab.fr/archaeocyatha/
• (UCMP Berkeley) Archaeocyathans
• (Palaeos Invertebrates) Archaeocyatha