| 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 |
Holasteroida is an order of irregular sea urchins.
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 :
Sand dollars are species of flat, burrowing sea urchins belonging to the order Clypeasteroida. Some species within the order, not quite as flat, are known as sea biscuits. Sand dollars can also be called "sand cakes" or "cake urchins".
The Aspidodiadematidae are a family of sea urchins.
Cassiduloida is an order of sea urchins. The group was extremely diverse with many families and species during the Mesozoic, but today, only seven extant species remain.
The heart urchins or Spatangoida are an order of sea urchins.
The Atelostomata are a type of sea urchins. They are distinguished from other sea urchins by their irregular shape and the absence of a feeding lantern. The group includes the well known heart urchins, as well as some less familiar and extinct forms.
Temnopleuridea is an infraorder of sea urchins in the order Camarodonta. They are distinguished from other sea urchins by the presence of large fused plates on top of the feeding lantern. The test is usually sculpted to some degree, and has perforated tubercles.
Cidaridae is a family of sea urchins in the order Cidaroida.
Spatangus is a genus of heart urchins in the Spatangidae family. The genus is synonymous with the previously recognised genera Prospatangus Lambert, 1902 and Spatagus. There are nine recognised species. The type species is Spatangus purpureus Müller, 1776 by subsequent designation.
Toxopneustidae is a family of globular sea urchins in the class Echinoidea.
Psychocidaridae is a family of sea urchins in the order Cidaroida. The genus Psychocidaris is extant while the other genera are only known from fossils. The family has been in existence since the Lower Jurassic (Toarcian) and the range includes Europe, Ukraine, North America, North Africa and the West Pacific.
Eucidaris is a genus of cidaroid sea urchins known as slate pencil urchins. They are characterised by a moderately thick test, a usually monocyclic apical disc, perforate and non-crenulate tubercles and nearly straight ambulacra with horizontal pore pairs. The primary spines are few and widely spaced, stout with blunt flat tips and beaded ornamentation and the secondary spines are short and apressed. They originated in the Miocene and extant members of the genus are found in the tropical Indo-Pacific Ocean, East Pacific, Atlantic Ocean and Caribbean Sea.
Irregularia is an extant infraclass of sea urchins that first appeared in the Lower Jurassic.
The Neognathostomata are a superorder of sea urchins.
The infraclassis Carinacea includes most living species of regular sea urchin, and fossil forms going back as far as the Triassic.
Hemicidaridae is a family of extinct sea urchins characterized by large, massive, club-shaped spines.
Hemipneustidae is an extinct family of sea urchins.
Dermechinus is a genus of sea urchin in the family Echinidae found in deep water in the southern Indian, Pacific and Atlantic Oceans. It is monotypic, with Dermechinus horridus, sometimes called the cactus urchin, being the only species.
The pourtalesiids (Pourtalesiidae) are a family of irregular sea urchins that live in the deep sea. They are secondarily bilateral-symmetrical and like other representatives of the taxon Holasteroida they lack the lantern of Aristotle, which is typical for many other sea urchins. The genus Pourtalesia was named after Louis-François de Pourtalès who first collected these animals while dredging at a depth of 600 m. The family is known already from the Upper Cretaceous (Maastrichtian) and is distributed worldwide.
Schizasteridae is a family of echinoderms belonging to the order Spatangoida.
Paleopneustina is a suborder of sea urchins of the order Spatangoida. Its taxonomy is still under investigation.
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