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| Chordates
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| Scientific classification | ||||||
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Subphylum Urochordata - Tunicates Ascidiacea Thaliacea Larvacea Subphylum Cephalochordata - Lancelets Subphylum Myxini - Hagfishes Subphylum Vertebrata - Vertebrates Petromyzontida - Lampreys Placodermi (extinct) Chondrichthyes - Cartilaginous fishes Acanthodii (extinct) Actinopterygii - Ray-finned fishes Actinistia - Coelacanths DipnoiFor the musical band, see Lungfish (band). see text Lungfishes are sarcopterygian fish that can breathe air (and in some species are obligate air-breathers), and have limb-like appendages instead of fins. There are six living species known; four in Africa - Lungfishes AmphibiaSubclass Labyrinthodontia extinct Subclass Lepospondyli extinct Subclass Lissamphibia Urodela Anura Gymnophiona The class Amphibia consists of all tetrapods (four-legged vertebrates) that do not have amniotic eggs. Amphibians generally spend part of their - Amphibians ReptiliaCrocodilia Crocodilians Rhynchocephalia Tuataras Squamata Suborder Sauria Lizards Suborder Serpentes Snakes Testudines Turtles Superorder Dinosauria Saurischia Ornithischia The reptiles are a group of vertebrate animals. Most reptiles are tetrapods, and t - Reptiles AvesFor other meanings of bird see bird (disambiguation). Many see text Birds are bipedal, warm-blooded, egg-laying vertebrates characterized primarily by feathers, forelimbs modified as wings, and hollow bones. There are almost 9000 known species of birds in - Birds MammalSubclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpia - Mammals |
Chordates ( phylumPhylum is one of the levels of scientific classification of organisms; see that article for more detail. In linguistics the term phylum was introduced in comparative work and means "super-family" of languages possibly being related. This is a disambiguati Chordata) include the vertebrates, together with several closely related invertebrateInvertebrate is a term coined by Chevalier de Lamarck to describe any animal without a backbone or vertebra, like insects, squids and worms. He divided them into two groups, the Insecta and the Vermes. However, the invertebrates are not a coherent group os. They are united by having, at some stage in their life, a notochordThe notochord consists of a rod of cells situated on the ventral aspect of the neural tube; it constitutes the foundation of the axial skeleton, since around it the segments of the vertebral column are formed. Its appearance synchronizes with that of the, a hollow dorsal nerve cord, pharyngeal slit s, a tail extending past the anus, and bands of muscles that go around the body.
The phylum Chordata is broken down into three subphyla: Urochordata, Cephalochordata, and Vertebrata. Urochordate larvae have a notochord and a nerve cord but they are lost in adulthood. Cephalochordates have a notochord and a nerve cord but no vertebrae. In vertebrates, the notochord has been replaced by a bony vertebral column.
The extant groups of chordates are related as shown in the phylogenetic tree, below. They do not match up very well with the traditional groups, and as a result vertebrate classification is in a state of flux, although their relationships are very well understood.
Chordata
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