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Sedentaria
Sedentaria is a diverse clade of annelid worms. It is traditionally treated as a subclass of the paraphyletic class Polychaeta, but it is also a monophyletic group uniting several polychaetes and the monophyletic class Clitellata. It is the sister group of Errantia. Phylogeny The phylogeny of polychaetes is slowly being resolved. Sedentaria and Errantia are the two biggest clades of polychaetes, and together they compose clade Pleistoannelida. Sedentaria's most basal clade is Orbiniida. Other groups that are nested within Sedentaria are: Clitellata, the Sabellida/Spionida clade, Opheliida, Echiura, Cirratuliformia, Terebelliformia, Maldanomorpha and the families Siboglinidae and Capitellidae. Some taxa, such as Spintheridae and Myzostomida, are still difficult to place due to their long branching, but they likely belong to either Errantia Errantia is a diverse group of marine polychaete worms in the phylum Annelida. Traditionally a subclass of the paraphyletic class "Polycha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pleistoannelida
Pleistoannelida is a group of annelid worms that comprises the vast majority of the diversity in phylum Annelida. Discovered through phylogenetic analyses, it is the largest clade of annelids, comprised by the last common ancestor of the highly diverse sister groups Errantia and Sedentaria (Clitellata and related polychaetes) and all the descendants of that ancestor. Phylogeny Pleistoannelida is composed by two big clades: Errantia (Eunicida, eunicids, siboglinids and related polychaetes) and Sedentaria (spoon worms, Siboglinidae, tubeworms, clitellates and related polychaetes). There are also smaller groups of difficult placement, such as Myzostomida and Spintheridae, that belong to either one of them. Closely related to Pleistoannelida is a grade of basal annelids: the Amphinomida/Sipunculida/''Lobatocerebrum'' clade, Chaetopterida and Palaeoannelida. A possible, closer sister group to Pleistoannelida could be Dinophiliformia, a clade containing interstitial (meiofaunal) genera p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Errantia
Errantia is a diverse group of marine polychaete worms in the phylum Annelida. Traditionally a subclass of the paraphyletic class "Polychaeta", it is currently regarded as a monophyletic group within the larger Pleistoannelida, composed of Errantia and Sedentaria. These worms are found worldwide in marine environments and brackish water. Phylogeny The phylogeny of polychaetes is slowly being resolved. Errantia and Sedentaria are the two biggest clades of polychaetes, and together they compose clade Pleistoannelida. Two groups are nested within Errantia: Aciculata (Eunicida + Phyllodocida) and Protodriliformia (small meiofaunal worms such as the Protodrilida). Historically, the order Amphinomida was part of this subclass. However, phylogenetic analyses place Amphinomida inside a basal clade with Sipunculida and '' Lobatocerebrum'', and this clade is the sister group to Pleistoannelida. Some taxa, such as Spintheridae and Myzostomida, are still difficult to place due to their lon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orbiniida
Orbiniida is an order of small polychaete worms in the phylum Annelida. It is the earliest diverging clade in Sedentaria. Along with Protodriliformia (in Errantia), this order is composed of meiofaunal marine life, marine worms formerly known as "Archiannelida, archiannelids". These worms inhabit the Marine life, marine interstitial ecosystem, the space between sand grains. Classification First mentioned in 1977, Orbiniida was an order of the polyphyletic infraclass "Scolecida" of the class "Polychaeta". It was composed of the families Orbiniidae, Paraonidae and Questidae, all of which share in common the lack of antennae and palps, and the presence of an eversible pharynx and biramous parapodia with simple chaetae. However, through phylogenetic analysis it was found that Questidae and Paraonidae are more closely related to Clitellata and Cirratulida respectively. Because of this, the taxonomic composition of Orbiniida was changed to exclude these two families and include several i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Annelid
The annelids (Annelida , from Latin ', "little ring"), also known as the segmented worms, are a large phylum, with over 22,000 extant species including ragworms, earthworms, and leeches. The species exist in and have adapted to various ecologies – some in marine environments as distinct as tidal zones and hydrothermal vents, others in fresh water, and yet others in moist terrestrial environments. The Annelids are bilaterally symmetrical, triploblastic, coelomate, invertebrate organisms. They also have parapodia for locomotion. Most textbooks still use the traditional division into polychaetes (almost all marine), oligochaetes (which include earthworms) and leech-like species. Cladistic research since 1997 has radically changed this scheme, viewing leeches as a sub-group of oligochaetes and oligochaetes as a sub-group of polychaetes. In addition, the Pogonophora, Echiura and Sipuncula, previously regarded as separate phyla, are now regarded as sub-groups of polycha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polychaetes
Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. More than 10,000 species are described in this class. Common representatives include the lugworm (''Arenicola marina'') and the sandworm or clam worm ''Alitta''. Polychaetes as a class are robust and widespread, with species that live in the coldest ocean temperatures of the abyssal plain, to forms which tolerate the extremely high temperatures near hydrothermal vents. Polychaetes occur throughout the Earth's oceans at all depths, from forms that live as plankton near the surface, to a 2- to 3-cm specimen (still unclassified) observed by the robot ocean probe ''Nereus'' at the bottom of the Challenger Deep, the deepest known spot in the Earth's oceans. Only 168 species (less than 2% of all polychaetes) are known from fresh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polychaete
Polychaeta () is a paraphyletic class (biology), class of generally marine invertebrate, marine annelid worms, common name, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. More than 10,000 species are described in this class. Common representatives include the lugworm (''Arenicola marina'') and the Alitta virens, sandworm or Alitta succinea, clam worm ''Alitta''. Polychaetes as a class are robust and widespread, with species that live in the coldest ocean temperatures of the abyssal plain, to forms which tolerate the extremely high temperatures near hydrothermal vents. Polychaetes occur throughout the Earth's oceans at all depths, from forms that live as plankton near the surface, to a 2- to 3-cm specimen (still unclassified) observed by the robot ocean probe Nereus (underwater vehicle), ''Nereus'' at the bottom of the Challenger Deep, the deepes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polychaeta
Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. More than 10,000 species are described in this class. Common representatives include the lugworm (''Arenicola marina'') and the sandworm or clam worm ''Alitta''. Polychaetes as a class are robust and widespread, with species that live in the coldest ocean temperatures of the abyssal plain, to forms which tolerate the extremely high temperatures near hydrothermal vents. Polychaetes occur throughout the Earth's oceans at all depths, from forms that live as plankton near the surface, to a 2- to 3-cm specimen (still unclassified) observed by the robot ocean probe ''Nereus'' at the bottom of the Challenger Deep, the deepest known spot in the Earth's oceans. Only 168 species (less than 2% of all polychaetes) are known from f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arenicolidae
Arenicolidae is a family of marine polychaete worms. They are commonly known as lugworms and the little coils of sand they produce are commonly seen on the beach. Arenicolids are found worldwide, mostly living in burrows in sandy substrates. Most are detritivores but some graze on algae. Description The arenicolids are characterised by an elongated cylindrical body separated into two or three distinct regions. The prostomium has no appendages or palps. There are one or two anterior segments without setae. On the other segments, all the setae are unbranched, including the capillary setae and the rostrate uncini. The notopodia are bluntly truncate and the neuropodia are elongated tori forming long transverse welts in some of the setigers. The notosetae have either a capillary function or act as limbs and the neurosetae are rostrate hooks. There are branchiae present on some of the setigers in the middle or posterior regions. Apart from the genus '' Branchiomaldane'', the lugwor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maldanidae
Maldanidae is a family of more than 200 species of Marine life, marine polychaetes commonly known as bamboo worms or maldanid worms. They belong to the order Capitellida, in the phylum Annelida. They are most closely related to family Arenicolidae, and together form the clade Maldanomorpha. Morphology Maldanid worms have a long and cylindrical body that usually bends at one or both ends. It can be divided into four parts: 1) a head, formed by a Dorsal (anatomy), dorsally positioned prostomium that is fused to the peristomium, sometimes with a flattened cephalic plate; 2) a thorax, formed by the first four wikt:chaetigers, chaetigers (i.e. Chaeta, chaetae-bearing metamery, segments), usually with strong spines; 3) an abdomen, with several longer chaetigers that are often followed by a number of achaetous (i.e. without Chaeta, chaetae) segments; 4) a posterior end, with a pygidium that contains the anus. The maldanid pygidium takes a wide variety of forms such as conical, plate-shaped ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spintheridae
Spintheridae is a family of marine polychaete worms with a single genus, ''Spinther'', containing these species: * '' Spinther alaskensis'' Hartman, 1948 * '' Spinther arcticus'' (M. Sars, 1851) (includes Spinther miniaceus'' Grube, 1860) *'' Spinther australiensis'' Augener, 1913 * '' Spinther citrinus'' (Stimpson, 1854) *'' Spinther ericinus'' Yamamoto & Imajima, 1985 *'' Spinther hystrix'' Uschakov, 1950 * '' Spinther japonicus'' Imajima and Hartman, 1964 * '' Spinther oniscoides'' Johnston, 1845 *'' Spinther sagamiensis'' Imajima, 2003 *'' Spinther usarpia'' Hartman, 1967 * '' Spinther vegae'' Augener, 1928 (includes '' Spinther wireni'' Hartman, 1948) The animal lives as a symbiont on sponges. Johnston's paper does not explain the choice of the name, but ancient Greek σπινθήρ means "spark." In images of the living animal, it appears to be surrounded by a cloud of pinpoints of light. References Polychaetes Taxa named by George Johnston (naturalist) {{anne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Taxon
In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and given a particular ranking, especially if and when it is accepted or becomes established. It is very common, however, for taxonomists to remain at odds over what belongs to a taxon and the criteria used for inclusion. If a taxon is given a formal scientific name, its use is then governed by one of the nomenclature codes specifying which scientific name is correct for a particular grouping. Initial attempts at classifying and ordering organisms (plants and animals) were set forth in Carl Linnaeus's Linnaean taxonomy, system in ''Systema Naturae'', 10th edition (1758), as well as an unpublished work by Bernard de Jussieu, Bernard and Antoine Laurent de Jussieu. The idea of a unit-based system of biological classification was first mad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monophyletic
In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic groups are typically characterised by shared derived characteristics ( synapomorphies), which distinguish organisms in the clade from other organisms. An equivalent term is holophyly. The word "mono-phyly" means "one-tribe" in Greek. Monophyly is contrasted with paraphyly and polyphyly as shown in the second diagram. A ''paraphyletic group'' consists of all of the descendants of a common ancestor minus one or more monophyletic groups. A '' polyphyletic group'' is characterized by convergent features or habits of scientific interest (for example, night-active primates, fruit trees, aquatic insects). The features by which a polyphyletic group is differentiated from others are not inherited from a common ancestor. These definitions have tak ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
