| Cyrtocrinida | |
|---|---|
 | |
| Holopus sp. | |
| Scientific classification | |
| Kingdom: | |
| Phylum: | |
| Class: | |
| Order: | Cyrtocrinida [1] |
Cyrtocrinida is an order of sea lilies which contains two suborders and three families.
| Cyrtocrinida | |
|---|---|
| | |
| Holopus sp. | |
| Scientific classification | |
| Kingdom: | |
| Phylum: | |
| Class: | |
| Order: | Cyrtocrinida [1] |
Cyrtocrinida is an order of sea lilies which contains two suborders and three families.
Members of this order have stems consisting of a single skeletal unit or a very small number of units. There are no cirri, and the expanded base of the stem attaches directly to the substrate. The calyx may be asymmetrical and consists of five arms attached to five radial ossicles. The arms subdivide at arm ossicle I or II. [2]
The World Register of Marine Species includes the following groups in the order: [1]
The Scyphozoa are an exclusively marine class of the phylum Cnidaria, referred to as the true jellyfish.
Crinoids are marine animals that make up the class Crinoidea, one of the classes of the phylum Echinodermata, which also includes the starfish, brittle stars, sea urchins and sea cucumbers. Those crinoids which, in their adult form, are attached to the sea bottom by a stalk are commonly called "sea lilies", while the unstalked forms are called "feather stars" or "comatulids", being members of the largest crinoid order, Comatulida. They live in both shallow water and in depths as great as 9,000 meters (30,000 ft).
Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea. Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish are also known as asteroids due to being in the class Asteroidea. About 1,900 species of starfish occur on the seabed in all the world's oceans, from warm, tropical zones to frigid, polar regions. They are found from the intertidal zone down to abyssal depths, at 6,000 m (20,000 ft) below the surface.
Sea cucumbers are echinoderms from the class Holothuroidea. They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the sea floor worldwide. The number of holothurian species worldwide is about 1,717, with the greatest number being in the Asia-Pacific region. Many of these are gathered for human consumption and some species are cultivated in aquaculture systems. The harvested product is variously referred to as trepang, namako, bêche-de-mer, or balate. Sea cucumbers serve a useful role in the marine ecosystem as they help recycle nutrients, breaking down detritus and other organic matter, after which bacteria can continue the decomposition process.
Sea spiders are marine arthropods of the order Pantopoda, belonging to the class Pycnogonida, hence they are also called pycnogonids. They are cosmopolitan, found in oceans around the world. There are over 1,300 known species, with legs ranging from 1 mm (0.04 in) to over 70 cm (2.3 ft). Most are toward the smaller end of this range in relatively shallow depths; however, they can grow to be quite large in Antarctic and deep waters.
Isopoda is an order of crustaceans that includes woodlice and their relatives. Isopods live in the sea, in fresh water, or on land. All have rigid, segmented exoskeletons, two pairs of antennae, seven pairs of jointed limbs on the thorax, and five pairs of branching appendages on the abdomen that are used in respiration. Females brood their young in a pouch under their thorax.
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.
The Valvatida are an order of starfish in the class Asteroidea, which contains 695 species in 172 genera in 17 families.
Discomedusae is a subclass of jellyfish in the class Scyphozoa. It is the sister taxon of Coronamedusae. Discomedusae contains about 155 named species and there are likely to be many more as yet undescribed. Jellyfish in this subclass are much more likely to have swarming events or form blooms than those in Coronamedusae. Discomedusae consists of two orders, Rhizostomae and Semaeostomeae.
Articulata are a subclass or superorder within the class Crinoidea, including the only living crinoid species. They are commonly known as sea lilies or feather stars. The Articulata are differentiated from the extinct subclasses by their lack of an anal plate in the adult stage and the presence of an entoneural system. Articulata first appeared in the fossil record during the Triassic period although other, now extinct crinoid groups, originated in the Ordovician.
The Forcipulatida are an order of sea stars, containing three families and 49 genera.
The Asterozoa are a subphylum in the phylum Echinodermata. Characteristics include a star-shaped body and radially divergent axes of symmetry. The subphylum includes the class Asteroidea, the class Ophiuroidea, and the extinct order Somasteroidea.
Antedon is a genus of free-swimming, stemless crinoids. The genus first appeared in the fossil record in the Cretaceous period.
Comatulida is an order of crinoids. Members of this order are known as feather stars and mostly do not have a stalk as adults. The oral surface with the mouth is facing upwards and is surrounded by five, often divided rays with feathery pinnules. Comatulids live on the seabed and on reefs in tropical and temperate waters.
Metacrinus rotundus, the Japanese sea lily, is a marine invertebrate, a species of stalked crinoid in the family Isselicrinidae. It is a species found off the west coast of Japan, and is living near the edge of the continental shelf, around 100–150m deep. This is the shallowest species among the extant stalked crinoids.
Bourgueticrinida is an order of crinoids that typically live deep in the ocean. Members of this order are attached to the seabed by a slender stalk and are known as sea lilies. While other groups of crinoids flourished during the Permian, bourgueticrinids along with other extant orders did not appear until the Triassic, following a mass extinction event in which nearly all crinoids died out.
Cenocrinus is a monotypic genus of stalked crinoids in the family Isselicrinidae. The great West Indian sea lily is the only species in the genus and is found in deep waters in the Caribbean Sea and Gulf of Mexico.
Leptometra is a genus of free-swimming, stemless crinoids.
Hyocrinida is an order of sea lilies which contains a single extant family, Hyocrinidae.
Notocrinus virilis is a marine invertebrate, a species of crinoid or feather star in the family Notocrinidae. It is found in deep water in the Southern Ocean around the coasts of Antarctica and adjacent islands. A sea snail sometimes parasitizes it.
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