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Image of Pourtalesia jeffreysi Thomson 1873
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Holasteroida Durham & Melville 1957

Holasteroida

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Holasteroida is an order of irregular sea urchins.

Characteristics

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Ceratophysa ceratopyga by A. Agassiz (1881)

These irregular sea urchins are characterized by a particularly marked bilateral symmetry, including for the apical system, which is highly elongated. In some contemporary abyssal groups such as Pourtalesiidae, some species are even bottle-shaped. The mouth (peristome) does not contain an Aristotle's lantern. The anus (periproct) has migrated towards the periphery of the test. The plastron is never amphisternous.[1]

This order seems to have appeared at the lower Cretaceous.[1]

List of families

According to World Register of Marine Species :

References

  1. ^ a b "Holasteroida". Echinoid Directory.
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Holasteroida: Brief Summary

provided by wikipedia EN

Holasteroida is an order of irregular sea urchins.

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cc-by-sa-3.0
copyright
Wikipedia authors and editors
original
visit source
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wikipedia EN