Holasteroida
Holasteroida is an order of irregular sea urchins.
| Holasteroida Temporal range:   | |
|---|---|
![]()  | |
| Pourtalesia wandeli | |
| Scientific classification  | |
| Kingdom: | Animalia | 
| Phylum: | Echinodermata | 
| Class: | Echinoidea | 
| Subclass: | Euechinoidea | 
| Infraclass: | Irregularia | 
| Superorder: | Atelostomata | 
| Order: | Holasteroida Durham & Melville, 1957  | 
Characteristics
    

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]

Echinosigra amphora (Pourtalesiidae)
This order seems to have appeared at the lower Cretaceous.[1]
List of families
    
According to World Register of Marine Species :
- Family Hemipneustidae (Lambert, 1917) †
- genus Hemipneustes L. Agassiz, 1835 †
 - genus Medjesia Jeffery, 1997 †
 - genus Opisopneustes Gauthier, 1889 †
 - genus Plesiohemipneustes Smith & Wright, 2003 †
 - genus Toxopatagus Pomel, 1883 †
 
 - Sub-order Meridosternata (Lovén, 1883)
- Infra-order Cardiasterina †
- Family Cardiasteridae Lambert, 1917 †
 - Family Stegasteridae Lambert, 1917f †
 
 - Family Echinocorythidae Wright, 1857 †
 - Family Holasteridae Pictet, 1857 †
- Genus Salvaster Saucède, Dudicourt & Courville, 2012 †
 
 - Infra-order Urechinina
- Family Calymnidae Mortensen, 1907
 - Family Carnarechinidae Mironov, 1993
 - Family Corystusidae Foster & Philip, 1978
 - Family Plexechinidae Mooi & David, 1996
 - Family Pourtalesiidae A. Agassiz, 1881
 - Family Urechinidae Duncan, 1889
 
 
 - Infra-order Cardiasterina †
 - Family Pseudholasteridae (Smith & Jeffery, 2000) †
- genus Eoholaster Solovjev, 1989 †
 - genus Giraliaster Foster & Philip, 1978 †
 - genus Pseudholaster Pomel, 1883 †
 - genus Taphraster Pomel, 1883 †
 
 - Family Stenonasteridae (Lambert, 1922) †
- genus Stenonaster Lambert, 1922 †
 
 
References
    
- "Holasteroida". Echinoid Directory.
 
- Holasteroida at the Natural History Museum
 - Kroh A, Mooi R (eds.). "Holasteroida". World Echinoidea Database. World Register of Marine Species.
 
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