AskDefine | Define chordate

Dictionary Definition

chordate adj : of or relating to or characteristic of the Chordata n : any animal of the phylum Chordata having a notochord or spinal column

User Contributed Dictionary

English

Pronunciation

  • a RP /ˈkɔːdeɪt/
  • a US /ˈkɔːrdeɪt/

Homophones

Noun

  1. A member of the phylum Chordata; numerous animals having a notochord at some stage of their development; in vertebrates this develops into the spine

Adjective

  1. Of such animals.

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.
chordate in Afrikaans: Chordata
chordate in Arabic: حبليات
chordate in Aragonese: Chordata
chordate in Asturian: Chordata
chordate in Min Nan: Chit-soh tōng-bu̍t
chordate in Bosnian: Hordati
chordate in Bulgarian: Хордови
chordate in Catalan: Cordat
chordate in Czech: Strunatci
chordate in Welsh: Cordog
chordate in Danish: Chordater
chordate in German: Chordatiere
chordate in Estonian: Keelikloomad
chordate in Modern Greek (1453-): Χορδωτά
chordate in Spanish: Chordata
chordate in Esperanto: Ĥorduloj
chordate in Basque: Kordatu
chordate in Persian: طنابداران
chordate in French: Chordés
chordate in Western Frisian: Rêchstringdier
chordate in Irish: Cordaigh
chordate in Galician: Chordata
chordate in Korean: 척색동물
chordate in Hindi: रीढधारी
chordate in Croatian: Svitkovci
chordate in Indonesian: Chordata
chordate in Interlingua (International Auxiliary Language Association): Chordatos
chordate in Icelandic: Seildýr
chordate in Italian: Chordata
chordate in Hebrew: מיתרניים
chordate in Georgian: ქორდიანები
chordate in Kurdish: Kordat
chordate in Latin: Chordata
chordate in Latvian: Hordaiņi
chordate in Luxembourgish: Chordadéieren
chordate in Lithuanian: Chordiniai
chordate in Limburgan: Chordata
chordate in Lojban: skoselti'e
chordate in Hungarian: Gerinchúrosok
chordate in Macedonian: Хордати
chordate in Malay (macrolanguage): Kordata
chordate in Dutch: Chordadieren
chordate in Japanese: 脊索動物
chordate in Norwegian: Ryggstrengdyr
chordate in Norwegian Nynorsk: Ryggstrengdyr
chordate in Occitan (post 1500): Chordata
chordate in Polish: Strunowce
chordate in Portuguese: Cordados
chordate in Romanian: Chordata
chordate in Quechua: Wasa tiwlliyuq
chordate in Russian: Хордовые
chordate in Sicilian: Chordata
chordate in Simple English: Chordate
chordate in Slovak: Chordáty
chordate in Slovenian: Strunarji
chordate in Serbian: Хордати
chordate in Serbo-Croatian: Svitkovci
chordate in Sundanese: Chordata
chordate in Finnish: Selkäjänteiset
chordate in Swedish: Ryggsträngsdjur
chordate in Telugu: కార్డేటా
chordate in Thai: สัตว์มีแกนสันหลัง
chordate in Vietnamese: Động vật có dây sống
chordate in Tonga (Tonga Islands): Monumanu filo siliva
chordate in Turkish: Kordalılar
chordate in Ukrainian: Хордові
chordate in Zeeuws: Chordabeêsten
chordate in Samogitian: Chuordėnē
chordate in Chinese: 脊索动物
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