Echinoderms (Phylum Echinodermata) are a phylum In biology, a phylum [note 1] is a taxonomic rank below Kingdom and above Class. "Phylum" is equivalent to the botanical term division of marine An ocean (from Greek Ωκεανός, Okeanos ) is a large body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface (~3.61 X 1014 m2) is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas animals Animals are a major group of mostly multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and independently. All animals are also. Echinoderms are found at every ocean depth, from the intertidal zone The intertidal zone is the area that is exposed to the air at low tide and underwater at high tide (for example, the area between tide marks). This area can include many different types of habitats, including steep rocky cliffs, sandy beaches, or wetlands (e.g., vast mudflats). The area can be a narrow strip, as in Pacific islands that have only a to the abyssal zone The abyssal zone is the abyssopelagic layer of pelagic zone that contains the very deep benthic communities near the bottom of oceans. "Abyss" is from the Greek word meaning "bottomless sea". At depths of 4,000 to 6,000 meters , this zone remains in perpetual darkness and never receives daylight. It is the deeper part of the. Aside from the problematic Arkarua Arkarua is a small, Precambrian disk-like fossil with a raised center, a number of radial ridges on the rim, and a five-pointed central depression marked with radial lines of 5 small dots from the middle of the disk center. The only known species, Arkarua adami, is 3 to 10 mm in diameter. Arkarua is known only from the Ediacaran beds of the, the first definitive members of the phylum appeared near the start of the Cambrian The Cambrian is the first geological period of the Paleozoic era, lasting from 542 ± 0.3 million years ago to 488.3 ± 1.7 million years ago ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the classical name for Wales, where period.
The phylum contains about 7,000 living species There are many definitions of what kind of unit a species is . A common definition is that of a group of organisms capable of interbreeding and producing fertile offspring of both genders, and separated from other such groups with which interbreeding does not (normally) happen. Other definitions may focus on similarity of DNA or morphology. Some, making it the second-largest grouping of deuterostomes Deuterostomes are a superphylum of animals. They are a subtaxon of the Bilateria branch of the subregnum Eumetazoa, and are opposed to the protostomes. Deuterostomes are distinguished by their embryonic development; in deuterostomes, the first opening (the blastopore) becomes the anus, while in protostomes it becomes the mouth. Deuterostomes are, after the chordates Chordates are animals which are either vertebrates or one of several closely related invertebrates. They are united by having, for at least some period of their life cycle, a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail. The phylum Chordata consists of three subphyla: Urochordata, represented by; they are also the largest phylum that has no freshwater or terrestrial representatives.
The word derives from the Greek Greek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical ancient Greek literature and the New Testament of εχινοδέρματα (echinodermata), plural of εχινόδερμα (echinoderma), "spiny A spine is a hard, thorny or needle-like structure which occurs on various animals. Animals such as porcupines and sea urchins grow spines as a self-defense mechanism. Spines are often formed of keratin. Other animals with spines are hedgehogs and spiny mice skin" and that from εχινός (echinos), "sea-urchin", originally "hedgehog"[1] + δέρμα (derma), "skin"[2][3].
The Echinoderms are important both biologically and geologically: biologically because few other groupings are so abundant in the biotic desert of the deep sea, as well as the shallower oceans, and geologically as their ossified skeletons are major contributors to many limestone formations, and can provide valuable clues as to the geological environment. Further, it is held by some that the radiation of echinoderms was responsible for the Mesozoic The Mesozoic Era is one of three geologic eras of the Phanerozoic eon. The division of time into eras dates back to Giovanni Arduino, in the 18th century, although his original name for the era now called the "Mesozoic" was "Secondary" . Lying between the Paleozoic and the Cenozoic, "Mesozoic" means "middle revolution Organisms which went into decline include stalked crinoids, articulate brachiopods, and endobyssate bivalves. Weakly armoured gastropods also disappeared, while more heavily armoured taxa diversified of marine life.
Two main subdivisions of Echinoderms are traditionally recognised: the more familiar, motile Eleutherozoa, which encompasses the Asteroidea (starfish Sea stars are echinoderms belonging to the class Asteroidea. The names "sea star" and "starfish" are sometimes differentiated, with "starfish" used in a broader sense to include the closely related brittle stars, which make up the class Ophiuroidea, as well as excluding sea stars which do not have exactly five arms,), Ophiuroidea (brittle stars Brittle stars, or ophiuroids, are echinoderms, closely related to sea stars. They crawl across the seafloor using their flexible arms for locomotion. The ophiuroids generally have five long slender, whip-like arms which may reach up to 60 centimeters in length on the largest specimens. They are also known as serpent stars), Echinoidea (sea urchins Sea urchins or urchins are small, spiny, globular animals that compose part of class Echinoidea. They are found in all oceans. Their shell, or "test", is round and spiny, typically from 3 to 10 centimetres across. Common colors include black and dull shades of green, olive, brown, purple, and red. They move slowly, feeding mostly on and sand dollars Sand dollars are any species of flattened, burrowing sea urchin belonging to the order Clypeasteroida. The most common sand dollar, Echinarachnius parma, is widespread in circumpolar ocean waters of the Northern Hemisphere, from the intertidal zone to considerable depths) and Holothuroidea (sea cucumbers Sea cucumbers are a class of marine animals with an elongated body and leathery skin, which is found on the sea floor worldwide. Many holothurian species and genera, informally known as sea cucumbers, are targeted for human consumption. The harvested product is also referred to as sea cucumber, or as trepang, bêche-de-mer, balate, or sea slug); and the sessile Pelmatazoa, which consists of the crinoids Crinoids, also known as sea lilies or feather-stars, are marine animals that make up the class Crinoidea of the echinoderms . Crinoidea comes from the Greek word krinon, "a lily", and eidos, "form". They live both in shallow water and in depths as great as 6,000 meters.[citation needed] and extinct Paracrinoids Paracrinoids, are extinct marine animals that make up the class Paracrinoidea of the echinoderms , and are closely related to crinoids. They lived in shallow seas during the Early Ordovician through the Early Silurian. Some crinoids, the feather stars Crinoids, also known as sea lilies or feather-stars, are marine animals that make up the class Crinoidea of the echinoderms . Crinoidea comes from the Greek word krinon, "a lily", and eidos, "form". They live both in shallow water and in depths as great as 6,000 meters.[citation needed], have secondarily re-evolved a free-living lifestyle.
A fifth class of Eleutherozoa consisting of just two species, the Concentricycloidea (sea daisies Sea daisies make up an unusual group of deep-sea taxa belonging to the phylum Echinodermata, with three species described in the genus Xyloplax), were recently[4] merged into the Asteroidea. The fossil record contains a host of other classes which do not appear to fall into any extant crown group A crown group is the smallest monophyletic group, or "clade", to contain the last common ancestor of all extant members, and all of that ancestor's descendants. Extinct organisms can still be part of a crown group: for instance, the extinct dodo is still descended from the last common ancestor of all living birds, so falls within the.
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Deep-Sea News
Mosher and Watling report that the species Phiocreas oedipus, an echinoderm that kills its father and marries it mother, is only found on the octocoral ...
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Thelenota ananas
PaleoPoet
Sun, 11 Oct 2009 02:16:00 GM
Crinoidal limestone Filled with bodily pieces Portraying decay.
