Eocrinoidea

Eocrinoidea Temporal range: Cambrian–Silurian PreꞒ Ꞓ O S D C P T J K Pg N
	Eocrinoid holdfasts (Middle Ordovician, Utah)
	Colourful reconstruction of Gogia ojenai
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Echinodermata
Subphylum:	†Blastozoa
Class:	†Eocrinoidea; Jaekel, 1899
Groups included
	Gogiida;
Cladistically included but traditionally excluded taxa
	Rhombifera; Diploporita; Paracrinoidea; Parablastoidea[citation needed]; Blastoidea; Coronoidea[citation needed];

The Eocrinoidea are an extinct class of echinoderms that lived between the Early Cambrian and Late Silurian periods. They are the earliest known group of stalked, arm-bearing echinoderms, and were the most common echinoderms during the Cambrian.

Eocrinoids were a paraphyletic group that may have been ancestral to six other classes: Rhombifera, Diploporita, Coronoidea, Blastoidea, Parablastoidea, and Paracrinoidea. They may also be the progenitors of the cystoids, who are believed to be ancestral to modern crinoids. The earliest genera had a short holdfast and irregularly structured plates. Later forms had a fully developed stalk with regular rows of plates. They were benthic suspension feeders, with five ambulacra on the upper surface, surrounding the mouth and extending into a number of narrow arms.^[5]^[6] An unusual Ordovician form was the conical Bolboporites with its single brachiole.^[7]^[8] See also List of echinodermata orders.

Phylogeny

Cladogram after Zamora & Smith, 2011:^[9]

Eocrinoidea

Kinzercystis

Lyracystis

	Titanocrinus

	Aethocrinus

Gogia

	Macrocystella

	Ridersia

References

^ Smith 1984, p. 439
^ Smith 1984, p. 439
^ Smith 1984, p. 439
^ Smith 1984, p. 439
^ Prothero, D.R.,2004, Bringing Fossils to Life; An Introduction to Paleobiology (2 ed.):New York, The McGraw-Hill companies, p. 324
^ Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 1007–1008. ISBN 978-0-03-056747-6.
^ Rozhnov, S.V. 2009. Eocrinoids and paracrinoids of the Baltic Ordovician basin: a biogeographical report. IGCP Meeting, Ordovician palaeogeography and palaeoclimate, Copenhagen, p. 16.
^ Rozhnov, S.V. and Kushlina, V.B. 1994. Interpretation of new data on Bolboporites Pander, 1830 (Echinodermata; Ordovician), p. 179-180, in David, B., Guille, A., Féral, J.-P. & Roux, M. (eds.), Echinoderms through time (Balkema, Rotterdam).
^ Samuel Zamora and A. B. Smith (2011). "Cambrian stalked echinoderms show unexpected plasticity of arm construction". Proceedings of the Royal Society B. 279 (1727): 293–298. doi:10.1098/rspb.2011.0777. PMC 3223674. PMID 21653588.

Works cited

Smith, Andrew B. (1984). "Classification of the Echinodermata". Palaeontology. 27 (3): 431–459.

External links

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[1] Smith 1984, p. 439

[2] Smith 1984, p. 439

[3] Smith 1984, p. 439

[4] Smith 1984, p. 439

[5] Prothero, D.R.,2004, Bringing Fossils to Life; An Introduction to Paleobiology (2 ed.):New York, The McGraw-Hill companies, p. 324

[IZ-6] Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 1007–1008. ISBN 978-0-03-056747-6.

[7] Rozhnov, S.V. 2009. Eocrinoids and paracrinoids of the Baltic Ordovician basin: a biogeographical report. IGCP Meeting, Ordovician palaeogeography and palaeoclimate, Copenhagen, p. 16.

[8] Rozhnov, S.V. and Kushlina, V.B. 1994. Interpretation of new data on Bolboporites Pander, 1830 (Echinodermata; Ordovician), p. 179-180, in David, B., Guille, A., Féral, J.-P. & Roux, M. (eds.), Echinoderms through time (Balkema, Rotterdam).

[Dibrachicystidae-9] Samuel Zamora and A. B. Smith (2011). "Cambrian stalked echinoderms show unexpected plasticity of arm construction". Proceedings of the Royal Society B. 279 (1727): 293–298. doi:10.1098/rspb.2011.0777. PMC 3223674. PMID 21653588.

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