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Helicoplacida (disused)
Taxonomy
Helicoplacida was named by Durham (1967).
It was assigned to Helicoplacoidea by Durham (1967) and Durham (1993).
It was assigned to Helicoplacoidea by Durham (1967) and Durham (1993).
Synonymy list
| Year | Name and author |
|---|---|
| 1967 | Helicoplacida Durham |
| 1993 | Helicoplacida Durham p. 600 |
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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.
Subcl. †Helicoplacida Durham 1967
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| J. W. Durham 1967 | Helicoplacoid echinoderms with test built of columns of plates; interambulacra extending from oral to apical poles, and composed of a median external column of plates and two lateral columns that may be folded inward or expanded laterally; ambulacra small, few in number, extending apically from mouth but not reaching apical pole. |