| Eocrinoidea Temporal range:
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|---|---|
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| Eocrinoid holdfasts (Middle Ordovician, Utah) | |
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| Colourful reconstruction of Gogia ojenai | |
Scientific classification
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Echinodermata |
| Subphylum: | †Blastozoa |
| Class: | †Eocrinoidea Jaekel, 1899 |
| Groups included | |
| |
| Cladistically included but traditionally excluded taxa | |
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.[1][2] An unusual Ordovician form was the conical Bolboporites with its single brachiole.[3][4] See also List of echinodermata orders.