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Nucleocrinida
Taxonomy
Nucleocrinida was named by Waters and Horowitz (1993).
It was assigned to Spiraculata by Waters and Horowitz (1993).
It was assigned to Spiraculata by Waters and Horowitz (1993).
Subtaxa
Synonymy list
| Year | Name and author |
|---|---|
| 1993 | Nucleocrinida Waters and Horowitz p. 211 |
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If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
Or. †Nucleocrinida Waters and Horowitz 1993
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Fm. †Nucleocrinidae Bather 1899
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G. †Nucleocrinus Conrad 1842
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†Nucleocrinus bosei Sumrall et al. 2009
†Nucleocrinus elegans Conrad 1842
†Nucleocrinus obovatus Barris 1883
Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| J.A. Waters and A.S. Horowitz 1993 | Godoniform to spherical theca; ten spiracles and separateanus; very long deltoids; narrow ambulacra, lancets not exposed;oral plates (five or more); includes the Nucleocrinidae. The nucleocrinids comprise three closely related genera(Elaeacrinus, Nucleocrinus, Placoblastusi in the family Nucleocrinidae.The orderisexclusivelyDevonianandhadits greatest specificand generic diversity in the Middle Devonian of eastern North America. The nucleocrinids are characterizedby 10 spiracles, a separate anus, and globose shapes in whichthe deltoids are the dominant plates of the theca. On the basis of shape and the pattern of spiracles, the nucleocrimds could be ancestral to the granatocrinids, but this wouldrequire reduction ofthe large deltoids that constitute most of the theca. This is not consistent with deltoid trends within the blastoids, and we consider it an unlikely scenario (also see granatocrinid discussion below); hence, the nucleocrinids are given ordinal status as a separate lineage. Nucleocrinid origins are presently a mystery. Globose shapes are typically an advanced character within the blastoids. |