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Order of sea urchins From Wikipedia, the free encyclopedia
Holasteroida is an order of irregular sea urchins.
Holasteroida Temporal range: | |
---|---|
Pourtalesia wandeli | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Echinodermata |
Class: | Echinoidea |
Subclass: | Euechinoidea |
Infraclass: | Irregularia |
Superorder: | Atelostomata |
Order: | Holasteroida Durham & Melville, 1957 |
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]
According to World Register of Marine Species :
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