| Ophiurida | |
|---|---|
 | |
| Ophiura ophiura | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Echinodermata |
| Class: | Ophiuroidea |
| Order: | Ophiurida Müller and Troschel, 1840 |
| Suborders | |
See text. | |
The Ophiurida are an order of echinoderms within the class Ophiuroidea. It includes the vast majority of living brittle stars.
Ophiurida have bursae for respiration and excretion, and dorsal and ventral arm shields are present and usually well developed. Arms are unbranched and incapable of coiling vertically. Most are five-armed, some with 4 or 6 arms as an abnormality, but others properly bear six or seven arms. The madreporite is on the oral surface. The digestive glands are entirely within the central disc. [2] They move their arms side to side by means of ball-and-socket joints. Tropical species tend to contrast color from the environment, but most others prefer to blend in. These biochromes do not include echinochromes.
There is currently no consensus as to the subdivision of the Ophiurida. The order has been divided into the following suborders and infraorders [3]
Another classification scheme divides it into the following suborders: [4]
Another classification scheme divides it as: [5]
Ophiurida have a world-wide distribution range and are found in oceans in different depths. Most of them are herbivores or detritus feeders.
The Apicomplexa are a large phylum of parasitic alveolates. Most of them possess a unique form of organelle that comprises a type of non-photosynthetic plastid called an apicoplast, and an apical complex structure. The organelle is an adaptation that the apicomplexan applies in penetration of a host cell.
The Tetraodontiformes are an order of highly derived ray-finned fish, also called the Plectognathi. Sometimes these are classified as a suborder of the order Perciformes. The Tetraodontiformes are represented by 10 extant families and at least 349 species overall; most are marine and dwell in and around tropical coral reefs, but a few species are found in freshwater streams and estuaries. They have no close relatives, and descend from a line of coral-dwelling species that emerged around 80 million years ago.
Brittle stars, serpent stars, or ophiuroids are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locomotion. The ophiuroids generally have five long, slender, whip-like arms which may reach up to 60 cm (24 in) in length on the largest specimens.
Eucarida is a superorder of the Malacostraca, a class of the crustacean subphylum, comprising the decapods, krill, Amphionides and Angustidontida. They are characterised by having the carapace fused to all thoracic segments, and by the possession of stalked eyes.
The Phrynophiurida are an order of brittle stars containing the basket stars.
The Gnathophiurina are a group of Ophiuroidea mostly treated as suborder.
Amphiuridae are a large family of brittle stars of the suborder Gnathophiurina. Some species are used to study echinoderm development and bioluminescence.
The Euryalida are an order of brittle stars, which includes large species with either branching arms or long and curling arms.
Ophiocanops fugiens is a living species in the brittle star family Ophiocanopidae. Though once considered to be the only one living species in this brittle star family, recent research has brought to light three specimens of Ophiocanops that differ substantially from O. fugiens. It has been regarded as the most primitive brittle star, close to Paleozoic forms, though other authors have disagreed with the view. Classification of O. fugiens is highly argued. Ophiocanops is usually placed in the order Oegophiurida or regarded as a genus incertae sedis or even given its own subclass Oegophiuridea. Some recent data suggest its relationship to the extant family Ophiomyxidae.
Ophiurina are a suborder of brittle stars containing the majority of living brittle star species.
Ophiuridae are a large family of brittle stars of the suborder Ophiurina.
Ophionereididae are a family of brittle stars.
Ophiocomidae are a family of brittle stars of the suborder Ophiurina.
Endeostigmata is a suborder of acariform mites. There are about ten families in Endeostigmata. The grouping is strongly suspected to be paraphyletic, containing unrelated early diverging lineages of mites.
Ophiopetra is a genus of prehistoric brittle stars. It lived in lagoons in Solnhofen Plattenkalk Formation. It has only one known species, Ophiopetra lithographica.
Polypodiineae is a suborder of ferns in the order Polypodiales. It is equivalent to the clade eupolypods I in earlier systems, and to the very broadly defined family Polypodiaceae in the classification of Christenhusz & Chase (2014). It probably diverged from the suborder Aspleniineae during the mid-Cretaceous. The divergence is supported by both molecular data and an often overlooked morphological characteristic which lies in the vasculature of the petiole. Most species that make up the suborder have three vascular bundles. The only exceptions are the grammitid ferns which have one, and the genus Hypodematium which has two. This differs from eupolypods II which mostly have two vascular bundles.
Ophiura ophiura or the serpent star is a species of brittle star in the order Ophiurida. It is typically found on coastal seabeds around northwestern Europe.
Ophiocomina nigra, commonly known as the black brittle star or black serpent star, is a species of marine invertebrate in the order Ophiurida. It occurs in the north-eastern Atlantic Ocean, the North Sea and the Mediterranean Sea.
The biological systematics and taxonomy of invertebrates as proposed by Richard C. Brusca and Gary J. Brusca in 2003 is a system of classification of invertebrates, as a way to classify animals without backbones.
Ophiomusa is a genus of echinoderms belonging to the family Ophiolepididae that includes: sea urchins, sand dollars and sea cucumbers. Ophiurida are similar to starfish; they both have a central disc and five arms sprouting from the disc. One of the main distinguishing factors of an Ophiuroid is its arms; the arms of an Ophiurida are longer, thinner, and distinctly separated in comparison to those of a sea star.
 | This Ophiuroidea-related article is a stub. You can help Wikipedia by expanding it. |