Biology:Eocrinoidea
The Eocrinoidea were an extinct class of echinoderms that lived between the Early Cambrian and Late Silurian periods. They are the earliest known group of stalked, brachiole-bearing echinoderms, and were the most common echinoderms during the Cambrian.
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.[1][2]
Phylogeny
Eocrinoids were a paraphyletic group that are seen as the basal stock from which all other blastozoan groups evolved.[3]
Early evolution
The following cladogram, after Nardin et al. 2017 with slight modifications,[4] shows the progression of early eocrinoid families, with all other eocrinoid families (including representatives Trachelocrinus and Ridersia) grouped with "derived Blastozoans" as their relationships with each other and with other blastozoans are not addressed.
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Relationships to other groups
Relationships among the eocrinidae and other blastozoan clades are an area of ongoing study. Below are two of many cladograms showing some aspect of eocrinoid paraphyly or polyphyly.
Stalked Cambrian (and select Ordovician) echinoderms, after Zamora & Smith, 2011.[5] All genera except those bracketed as "Crinoids" are blastozoans.
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References
- ↑ Prothero 2004, p. 324
- ↑ Barnes 1982
- ↑ Smith 1984, p. 439
- ↑ Nardin et al. 2017, p. 680 (Note: This source misspells "Lichenoididae" as "Lichenoidae", contrary to the Treatise on Invertebrate Paleontology, Part S, Echinodermata 1, and incorrectly (per PBDB) and IRMNG) includes Lyracystis in Eocrinidae instead of Lyracystidae; this cladogram shows the more common spellings and placements.)
- ↑ Zamora & Smith 2011
- ↑ Paul et al. 2024, p. 12–13 (Note: The text groups Sanducystis with eocrinoids as the outgroup, but the paper cited classifies it as a glyptocystitoid; it is shown un-bracketed on this page. Similarly, the text classifies Macurdablastus as a eublastoid, but the cited paper has it as the sister of Eublastoidea; it is shown outside of Eublastoidea on this page.)
Works cited
- Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 1007–1008. ISBN 978-0-03-056747-6.
- Jell, Peter A.; Sprinkle, James (2021). "Revision of Whitehouse’s eocrinoids Peridionites and Cymbionites, with description of the associated fauna including two new echinoderm genera, lower Middle Cambrian Thorntonia Limestone, northwestern Queensland". Alcheringa: An Australasian Journal of Palaeontology 45 (1): 1–55. doi:10.1080/03115518.2021.1913512.
- Nardin, Elise; Lefebvre, Bertrand; Fatka, Oldřich; Nohejlová, Martina; Kašička, Libor; Šinágl, Miroslav; Szabad, Michal (2017). "Evolutionary implications of a new transitional blastozoan echinoderm from the middle Cambrian of the Czech Republic". Journal of Paleontology 91 (4): 672–684. doi:10.1017/jpa.2016.157. Bibcode: 2017JPal...91..672N.
- Parsley, R. L. (2021). "Evolution, Functional Morphology and Paedomorphism in the Gogiid-Ascocystitid Lineage (Eocrinoidea; Cambrian-Ordovician)". Paleontological Journal 55 (9): 966–976. doi:10.1134/S0031030121090100. Bibcode: 2021PalJ...55..966P.
- Paul, Christopher R. C.; Lefebvre, Bertrand; Nohejlová, Martina; Zamora, Samuel (2024). "Rhombifera Barrande, 1867, and the origin of the Blastoidea (Echinodermata, Blastozoa)". Spanish Journal of Palaeontology 39: 90. doi:10.7203/sjp.28729.
- Prothero, D. R. (2004). Bringing Fossils to Life; An Introduction to Paleobiology (2 ed.). New York: The McGraw-Hill companies.
- Smith, Andrew B. (1984). "Classification of the Echinodermata". Palaeontology 27 (3): 431–459.
- Ubaghs, Georges (1967). "Eocrinoidea". Treatise on Invertebrate Paleontology, Part S: Echinodermata 1. 1. University of Kansas Press. pp. S455–S495. https://journals.ku.edu/InvertebratePaleo/issue/view/519. Retrieved 29 October 2024.
- Zamora, Samuel; Smith, A. B. (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. PMID 21653588.
Wikidata ☰ Q149514 entry
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