Calcareous sponge

Calcareous sponges; Temporal range: Cambrian Series 2 to present
	"Calcispongiae" from Ernst Haeckel's Kunstformen der Natur, 1904
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Porifera
Class:	Calcarea; Bowerbank, 1864
Subclasses
	Calcinea; Calcaronea

The calcareous sponges^[2]^[3] (class Calcarea) are members of the animal phylum Porifera, the cellular sponges. They are characterized by spicules made of calcium carbonate, in the form of high-magnesium calcite or aragonite. While the spicules in most species are triradiate (with three points in a single plane), some species may possess two- or four-pointed spicules.^[4]^[5] Unlike other sponges, calcareans lack microscleres, tiny spicules which reinforce the flesh. In addition, their spicules develop from the outside-in, mineralizing within a hollow organic sheath.^[6]

^ "Calcarea". paleobiodb.org. Retrieved 2021-08-22.
^ Richard Hertwig (1912). A Manual of Zoology. Translated by J. S. Kingsley. New York: Henry Holt & Co. p. 204. The calc sponges are exclusively marine and mostly live in shallow water.
^ Cite error: The named reference Barnes was invoked but never defined (see the help page).
^ Treatise on Invertebrate Paleontology Part E, Revised. Porifera, Volume 3: Classes Demospongea, Hexactinellida, Heteractinida & Calcarea, xxxi + 872 p., 506 fig., 1 table, 2004, available here. ISBN 0-8137-3131-3.
^ Treatise on Invertebrate Paleontology Part E, Revised. Porifera, Volumes 4 & 5: Hypercalcified Porifera, Paleozoic Stromatoporoidea & Archaeocyatha, liii + 1223 p., 665 figs., 2015, available here. ISBN 978-0-9903621-2-8.
^ Botting, Joseph P.; Butterfield, Nicholas J. (2005). "Reconstructing early sponge relationships by using the Burgess Shale fossil Eiffelia globosa , Walcott". Proceedings of the National Academy of Sciences. 102 (5): 1554–1559. doi:10.1073/pnas.0405867102. ISSN 0027-8424. PMC 547825. PMID 15665105.

[1] "Calcarea". paleobiodb.org. Retrieved 2021-08-22.

[Hertwig1912-2] Richard Hertwig (1912). A Manual of Zoology. Translated by J. S. Kingsley. New York: Henry Holt & Co. p. 204. The calc sponges are exclusively marine and mostly live in shallow water.

[Barnes-3] Cite error: The named reference Barnes was invoked but never defined (see the help page).

[:0-4] Treatise on Invertebrate Paleontology Part E, Revised. Porifera, Volume 3: Classes Demospongea, Hexactinellida, Heteractinida & Calcarea, xxxi + 872 p., 506 fig., 1 table, 2004, available here. ISBN 0-8137-3131-3.

[:1-5] Treatise on Invertebrate Paleontology Part E, Revised. Porifera, Volumes 4 & 5: Hypercalcified Porifera, Paleozoic Stromatoporoidea & Archaeocyatha, liii + 1223 p., 665 figs., 2015, available here. ISBN 978-0-9903621-2-8.

[:2-6] Botting, Joseph P.; Butterfield, Nicholas J. (2005). "Reconstructing early sponge relationships by using the Burgess Shale fossil Eiffelia globosa , Walcott". Proceedings of the National Academy of Sciences. 102 (5): 1554–1559. doi:10.1073/pnas.0405867102. ISSN 0027-8424. PMC 547825. PMID 15665105.

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Calcareous sponges Temporal range: Cambrian Series 2 to present^[1]

"Calcispongiae" from Ernst Haeckel's Kunstformen der Natur, 1904
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Porifera
Class:	Calcarea Bowerbank, 1864
Subclasses
Calcinea Calcaronea