AskDefine | Define chordata

Dictionary Definition

Chordata n : comprises true vertebrates and animals having a notochord [syn: phylum Chordata]

User Contributed Dictionary

Translingual

Etymology

chorda, chord, catgut, string

Proper noun

Chordata
  1. A taxonomic phylum, within superphylum Deuterostomia - animals having a notochord at some stage of their development.

Translations

a taxonomic phylum, within superphylum Deuterostomia

See also

Extensive Definition

Chordates (phylum Chordata) are a group of animals that includes the vertebrates, together with several closely related invertebrates. They are united by having, at some time in their life cycle, a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail. Some scientists argue that the true qualifier should be pharyngeal pouches rather than slits.
The phylum Chordata is broken down into three subphyla: Urochordata, Cephalochordata, and Vertebrata. Some consider the Hemichordata a fourth chordate subphylum, but they are usually treated as a separate phylum. Urochordate larvae have a notochord and a nerve cord but these are lost in adulthood. Cephalochordates have a notochord and a nerve cord but no vertebrae. In all vertebrates except for Hagfish, the dorsal hollow nerve cord has been surrounded with cartilaginous or bony vertebrae and the notochord generally reduced.
The chordates and three sister phyla, the hemichordates, the echinoderms and the xenoturbellidae, make up the deuterostomes, a superphylum. The chordates are the largest phylum among the deuterostomes.
The extant groups of chordates are related as shown in the phylogenetic tree below. Many of the taxa listed do not match traditional classes because several of those classes are paraphyletic. Different attempts to organize the profusion of chordate clades into a small number of groups, some with and some without paraphyletic taxa, have thrown vertebrate classification into a state of flux. Also, the relationships of some chordate groups are not very well understood.

Classification

Taxonomy

The following schema is from the third edition of Vertebrate Palaeontology. While it is structured so as to reflect evolutionary relationships (similar to a cladogram), it also retains the traditional ranks used in Linnaean taxonomy.

Phylogeny

Note: Lines show probable evolutionary relationships, including extinct taxa, which are denoted with a dagger, †. Some are invertebrates. Chordata is a phylum.

Origins

The origin of chordates is currently unknown. The first clearly-identifiable chordates are reduced fish- or lancelet-like specimens from the Cambrian. Most speculations about their origin fit into one or more of these categories:
  • A sediment-dwelling worm-like animal that evolved a flatter body and/or fins for swimming.
  • A sessile tubular filter-feeder that evolved into a free-swimming animal via usage of fins. (Tunicates, considered a chordate, are sessile filter feeders that have a tadpole-like larvae.)
  • A drifting or swimming larva of some other kind of animal that eventually retained its swimming features into adulthood.
The notochord's stiffness in many chordates may have evolved to facilitate the effectiveness of alternating muscle contractions for swimming (in S-shaped movements). In other words, in order to bend the body, a muscle needs a rigid structure to pull against, and a notochord (at least before spines) is the main structure to provide this. Lack of a stiff body part would merely result in the shorting of the animal during muscle contractions instead of the bending motions needed for swimming.
chordata in Afrikaans: Chordata
chordata in Arabic: حبليات
chordata in Aragonese: Chordata
chordata in Asturian: Chordata
chordata in Min Nan: Chit-soh tōng-bu̍t
chordata in Bosnian: Hordati
chordata in Bulgarian: Хордови
chordata in Catalan: Cordat
chordata in Czech: Strunatci
chordata in Welsh: Cordog
chordata in Danish: Chordater
chordata in German: Chordatiere
chordata in Estonian: Keelikloomad
chordata in Modern Greek (1453-): Χορδωτά
chordata in Spanish: Chordata
chordata in Esperanto: Ĥorduloj
chordata in Basque: Kordatu
chordata in Persian: طنابداران
chordata in French: Chordés
chordata in Western Frisian: Rêchstringdier
chordata in Irish: Cordaigh
chordata in Galician: Chordata
chordata in Korean: 척색동물
chordata in Hindi: रीढधारी
chordata in Croatian: Svitkovci
chordata in Indonesian: Chordata
chordata in Interlingua (International Auxiliary Language Association): Chordatos
chordata in Icelandic: Seildýr
chordata in Italian: Chordata
chordata in Hebrew: מיתרניים
chordata in Georgian: ქორდიანები
chordata in Kurdish: Kordat
chordata in Latin: Chordata
chordata in Latvian: Hordaiņi
chordata in Luxembourgish: Chordadéieren
chordata in Lithuanian: Chordiniai
chordata in Limburgan: Chordata
chordata in Lojban: skoselti'e
chordata in Hungarian: Gerinchúrosok
chordata in Macedonian: Хордати
chordata in Malay (macrolanguage): Kordata
chordata in Dutch: Chordadieren
chordata in Japanese: 脊索動物
chordata in Norwegian: Ryggstrengdyr
chordata in Norwegian Nynorsk: Ryggstrengdyr
chordata in Occitan (post 1500): Chordata
chordata in Polish: Strunowce
chordata in Portuguese: Cordados
chordata in Romanian: Chordata
chordata in Quechua: Wasa tiwlliyuq
chordata in Russian: Хордовые
chordata in Sicilian: Chordata
chordata in Simple English: Chordate
chordata in Slovak: Chordáty
chordata in Slovenian: Strunarji
chordata in Serbian: Хордати
chordata in Serbo-Croatian: Svitkovci
chordata in Sundanese: Chordata
chordata in Finnish: Selkäjänteiset
chordata in Swedish: Ryggsträngsdjur
chordata in Telugu: కార్డేటా
chordata in Thai: สัตว์มีแกนสันหลัง
chordata in Vietnamese: Động vật có dây sống
chordata in Tonga (Tonga Islands): Monumanu filo siliva
chordata in Turkish: Kordalılar
chordata in Ukrainian: Хордові
chordata in Zeeuws: Chordabeêsten
chordata in Samogitian: Chuordėnē
chordata in Chinese: 脊索动物
Privacy Policy, About Us, Terms and Conditions, Contact Us
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2
Material from Wikipedia, Wiktionary, Dict
Valid HTML 4.01 Strict, Valid CSS Level 2.1