Ecdysozoa Fossil range: Ediacaran or Early Cambrian - Recent
Centipede
Scientific classification
Kingdom: Animalia Subkingdom: Eumetazoa (unranked) Bilateria Superphylum: Ecdysozoa Aguinaldo et al., 1997
Phyla
Scalidophora (288 species)   Priapulida (16 species)   Kinorhyncha (150 species)   Loricifera (122 species) Nematoda (20,000+ species) Nematomorpha (320 species) Panarthropoda (6,181,000-10,193,000+ species)   Onychophora (200 species)   Tardigrada (1,000+ species)   Arthropoda (6,180,000-10,192,000+ species)

The Ecdysozoa are a group of protostome animals, including the Arthropoda (insects, arachnids, crustaceans, et cetera), Nematoda, and several smaller phyla. They were first defined by Aguinaldo et al. in 1997, based mainly on trees constructed using 18S ribosomal RNA genes.^[1] The group is also supported by morphological characters, and can be considered as including all animals that shed their exoskeleton (see ecdysis). Groups corresponding roughly to the Ecdysozoa had been proposed previously by Perrier in 1897 and Seurat in 1920 based on morphology alone. The Ediacaran Period (from the Ediacara Hills of South Australia) is the last geological period of the Neoproterozoic Era, just before the Cambrian. ... The Early Cambrian is an geological epoch that is part of the Cambrian Era. ... Operation Autumn Clouds: Israel Defense Forces troops kill two Palestinian terrorists in anorthern Gaza Strip operation. ... Download high resolution version (800x700, 156 KB)Centipede in peat marshlands of Kawai Nui, Oahu, Hawaii photographed by Eric Guinther and released under the GNU Free Documentation License for use at Wikipedia. ... Orders and Families See text Centipedes (Class Chilopoda) are fast-moving venomous, predatory, terrestrial arthropods that have long bodies and many jointed legs. ... Scientific classification or biological classification is a method by which biologists group and categorize species of organisms. ... For other uses, see Animal (disambiguation). ... subgroups Ctenophora Cnidaria Bilateria Eumetazoa is a clade comprising all major animal groups except sponges. ... Illustration of the different types of symmetry of Life Forms On Earth. ... Phylum (plural: phyla) is a taxon used in the classification of animals, adopted from the Greek phylai the clan-based voting groups in Greek city-states. ... Scalidophora is a group of marine pseudocoelomate invertebrates, consisting of the three phyla Kinorhyncha, Priapulida, and Loricifera. ... Priapulida (priapulid worms or penis worms, from Gr. ... Orders Cyclorhagida Homalorhagida Kinorhyncha (Gr. ... Loricifera is a small phylum of marine sediment-dwelling animals with about a dozen known species. ... Classes Adenophora    Subclass Enoplia    Subclass Chromadoria Secernentea    Subclass Rhabditia    Subclass Spiruria    Subclass Diplogasteria The roundworms (Phylum Nematoda) are one of the most common phyla of animals, with over 20,000 different described species. ... Classes Nectonematoida Gordioidea Nematomorpha (sometimes called Gordiacea, and commonly known as horsehair worms or Gordian worms) are a phylum of parasitic animals which are morphologically and ecologically similar to nematode worms, hence the name. ... Panarthropoda is a taxon combining the Phyla Arthropoda, Tardigrada and Onychophora. ... Genera Peripatus . ... Classes Heterotardigrada Mesotardigrada Eutardigrada Tardigrades (Tardigrada), or water bears, are a phylum of small, segmented animals, similar and related to the Arthropods. ... Subphyla and Classes Subphylum Trilobitomorpha Trilobita - Trilobites (extinct) Subphylum Chelicerata Arachnida - Spiders, Scorpions, etc. ... Groups Ecdysozoa Lophotrochozoa Platyzoa Protostomes (from the Greek: first the mouth) are a taxon of animals. ... Subphyla and Classes Subphylum Trilobitomorpha Trilobita - trilobites (extinct) Subphylum Chelicerata Arachnida - spiders,scorpions, etc. ... Classes Adenophorea    Subclass Enoplia    Subclass Chromadoria Secernentea    Subclass Rhabditia    Subclass Spiruria    Subclass Diplogasteria The roundworms or nematodes (Phylum Nematoda from Gr. ... Phylum (plural: phyla) is a taxon used in the classification of animals, adopted from the Greek phylai the clan-based voting groups in Greek city-states. ... Year 1997 (MCMXCVII) was a common year starting on Wednesday (link will display full 1997 Gregorian calendar). ... Ribosomal RNA (rRNA), a type of RNA synthesized in the nucleolus by RNA Pol I, is the central component of the ribosome, the protein manufacturing machinery of all living cells. ... The term morphology in biology refers to the outward appearance (shape, structure, colour, pattern) of an organism or taxon and its component parts. ... An exoskeleton is an external anatomical feature that supports and protects an animals body. ... Ecdysis is the molting of the cuticula in arthropods and related groups (Ecdysozoa). ... 1897 (MDCCCXCVII) was a common year starting on Friday (see link for calendar). ... 1920 (MCMXX) was a leap year starting on Thursday. ...

Group characters

The most notable characteristic shared by ecdysozoans is a three-layered cuticle composed of organic material, which is periodically molted as the animal grows. This process is called ecdysis and gives the group its name. The Ecdysozoans lack locomotory cilia, produce mostly amoeboid sperm, and their embryos do not undergo spiral cleavage as in most other protostomes. Various other features are found in the group — for instance, both tardigrades, pycnogonids and roundworms have a triradiate pharynx. Eponychium is the anatomical term for the human cuticle In biology, the term cuticle or cuticula is given to to a variety of tough but flexible, non-mineral outer coverings of an organism, or part of an organism, that provide prtoection. ... Ecdysis is the molting of the cuticula in arthropods and related groups (Ecdysozoa). ... cross-section of two cilia, showing 9+2 structure A cilium (plural cilia) is a fine projection from a eukaryotic cell that constantly beats in one direction. ... Amoeba (Chaos diffluens) Foraminiferan (Ammonia tepida) Heliozoan (Actinophrys sol) Amoeboids are cells that move or feed by means of temporary projections, called pseudopods (false feet). ... For other uses, see Embryo (disambiguation). ... This article needs cleanup. ... The pharynx (plural: pharynges) is the part of the neck and throat situated immediately posterior to the mouth and nasal cavity, and cranial, or superior, to the esophagus, larynx, and trachea. ...

The Ecdysozoa include the following phyla: Arthropoda, Onychophora, Tardigrada, Kinorhyncha, Priapulida, Loricifera, Nematoda and Nematomorpha. A few other groups, such as the gastrotrichs, have been considered possible members but lack the main characters of the group, and are now placed elsewhere. The Arthropoda, Onychophora and Tardigrada have been grouped together as the Panarthropoda because they are distinguished by segmented body plans.^[2] Subphyla and Classes Subphylum Trilobitomorpha Trilobita - Trilobites (extinct) Subphylum Chelicerata Arachnida - Spiders, Scorpions, etc. ... Genera Peripatus . ... Classes Heterotardigrada Mesotardigrada Eutardigrada Tardigrades (Tardigrada), or water bears, are a phylum of small, segmented animals, similar and related to the Arthropods. ... Orders Cyclorhagida Homalorhagida Kinorhyncha (Gr. ... Priapulida (priapulid worms or penis worms, from Gr. ... Loricifera is a small phylum of marine sediment-dwelling animals with about a dozen known species. ... Classes Adenophora    Subclass Enoplia    Subclass Chromadoria Secernentea    Subclass Rhabditia    Subclass Spiruria    Subclass Diplogasteria The roundworms (Phylum Nematoda) are one of the most common phyla of animals, with over 20,000 different described species. ... Classes Nectonematoida Gordioidea Nematomorpha (sometimes called Gordiacea, and commonly known as horsehair worms or Gordian worms) are a phylum of parasitic animals which are morphologically and ecologically similar to nematode worms, hence the name. ... The gastrotrichs (from Greek gaster stomach and thrix hair) are a phylum of microscopic animals, found in fresh water and marine environments. ... Panarthropoda is a taxon combining the Phyla Arthropoda, Tardigrada and Onychophora. ...

The non-panarthropod members of Ecdysozoa have been grouped as Cycloneuralia but they are more usually considered paraphyletic. In phylogenetics, a grouping of organisms is said to be paraphyletic (Greek para = near and phyle = race) if all the members of the group have a common ancestor, but the group does not include all the descendants of the most recent common ancestor of all group members. ...

The grouping proposed by Aguinaldo et al. is not universally accepted. Some zoologists still hold to the view that Panarthropoda should be classified with Annelida and that Ecdysozoa are polyphyletic. Especially the highly derived roundworms, with their many parasitic taxa and a considerable number of autapomorphies continue to pose problems. Panarthropoda is a taxon combining the Phyla Arthropoda, Tardigrada and Onychophora. ... Classes and subclasses Class Polychaeta (paraphyletic?) Class Clitellata    Oligochaeta - Earthworms and others    Acanthobdellida    Branchiobdellida    Hirudinea - Leeches Class Myzostomida Class Archiannelida (polyphyletic) Class Echiura *Some authors consider the subclasses under Clitellata to be classes The annelids, collectively called Annelida, are a large phylum of animals, comprising the segmented worms, with about... In biology, a taxon is polyphyletic if it is descended from more than one root form (in Greek poly = many and phyletic = racial). ... A parasite is an organism that lives in or on the living tissue of a host organism at the expense of it. ... A taxon (plural taxa) is an element of a taxonomy, e. ... An autapomorphy in cladistics is a derived trait that is unique to a given taxon. ...

1. Cuticular epithelia are widely spread over diverse phyla of invertebrates (including some groups outside Ecdysozoa) and show a considerable degree of variation. They are believed to have evolved independently, at least in some groups. In Nematoda and Panarthropoda, the cuticle is different in both chemical composition and ultrastructure, which means that it may have evolved independently.
2. Molecular evidence for the monophyly of Ecdysozoa is also ambiguous.^[3]

One of the proposed solutions is to regard Ecdysozoa as a sister-group of Annelida,^[4] however the controversy is still far from closure.^[5] Eponychium is the anatomical term for the human cuticle In biology, the term cuticle or cuticula is given to to a variety of tough but flexible, non-mineral outer coverings of an organism, or part of an organism, that provide prtoection. ... In zootomy, epithelium is a tissue composed of a layer of cells. ... Classes and subclasses Class Polychaeta (paraphyletic?) Class Clitellata    Oligochaeta - Earthworms and others    Acanthobdellida    Branchiobdellida    Hirudinea - Leeches Class Myzostomida Class Archiannelida (polyphyletic) Class Echiura *Some authors consider the subclasses under Clitellata to be classes The annelids, collectively called Annelida, are a large phylum of animals, comprising the segmented worms, with about...

A partial phylogenetic tree of the Ecdysozoa hypothesis is as follows.^[6]

References

1. ^ Aguinaldo, A. M. A., J. M. Turbeville, L. S. Linford, M. C. Rivera, J. R. Garey, R. A. Raff, & J. A. Lake, 1997. Evidence for a clade of nematodes, arthropods and other moulting animals. Nature 387: 489-493.
2. ^ Paleos Invertebrates: Panarthropoda - URL retrieved February 17, 2007
3. ^ Blair, J. E. , Kazuho Ikeo, Takashi Gojobori and S. Blair Hedges The evolutionary position of nematodes BMC Evolutionary Biology 2002, 2:7 doi:10.1186/1471-2148-2-7 and a discussion in: Wägele, J. W., T. Erikson, P. Lockhart, & B. Misof (1999) The Ecdysozoa: Artifact or monophylum? Journal of Zoological Systematics and Evolutionary Research 37: 211-223; Wägele, J. W. & B. Misof. (2001) On quality of evidence in phylogeny reconstruction: a reply to Zrzavý's defence of the 'Ecdysozoa' hypothesis. J. Zool. Syst. Evol. Research 39:3, 165-176 (criticising Ecdysozoa) and Zrzavy, (2001) Ecdysozoa versus Articulata: clades, artifacts, prejudices J. Zool. Syst. Evol. Research 39:3, 159-163. (supporting Ecdysozoa)
4. ^ Nielsen, C. (2003) Proposing a solution to the Articulata–Ecdysozoa controversy. Zoologica Scripta 32:5, 475-482
5. ^ Jenner, Ronald A. Unleashing the force of cladistics? Metazoan phylogenetics and hypothesis testing. Integrative and Comparative Biology, Feb 2003
6. ^ Tree of Life web project - Bilateria - accessed January 8, 2007

February 17 is the 48th day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... January 8 is the 8th day of the year in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ...

External links

Wikispecies has information related to:

Ecdysozoa

• UCMP-Ecdysozoa introduction
• http://www.palaeos.com/Kingdoms/Animalia/Ecdysozoa.html
• http://www.nematodes.org/tardigrades/Tardigrades_and_Ecdysozoa.html
• http://chuma.cas.usf.edu/~garey/articulata.html
• http://chuma.cas.usf.edu/~garey/essential.html