Chordés

The chordés or twisted ( Chordata ) are one of Bilatérien S Deutérostomien S. Their nervous system, in the shape of tube, is located above the digestive tract, one says that chordés are épineuriens, contrary to the Protostomiens. Their name comes from the Notochorde , a cartilagineuse plate of mesodermic origin which plays a crucial role at the time of the Embryogenèse. It has moreover a role of support and protection of the nervous tube at the chordés primitive ones. At the vertebrate ones, which constitutes a subphylum of chordés, the notochorde generally regresses at the adulthood to be replaced by the spinal column. Twisted are also characterized by a pharynx (left former the digestive tract), bored slits branchiales at least in an embryonic state and by a circulatory system closed with a heart.

This junction knew a very important diversification since its appearance with the Cambrien (towards 500 [[million years My]], supposed present in the Faune of Burgess with the individual Pikaia ): whereas the céphalochordés and the urochordé S remained little diversified and exclusively sailors, the vertebrate ones had a fulgurating evolution and conquered all the mediums of planets, with their first steps on ground with the higher Dévonien (there are approximately 370 My). Today, with the Baleine S, they include/understand the largest animals that the ground ever carried.

Among twisted, one finds:

Urochordés or tunicates
Céphalocordés (Amphioxus)
Vertebrate

See too

Celebrity

List classes

In traditional Classification, chordés is composed of:

subphylum Cephalochordata
subphylum Tunicata Lamarck, 1816 -- Tunicier S

class Appendicularia -- Tunicier S Pelagic S
class Ascidiacea -- Ascidie S
class Thaliacea -- Tunicier S Pelagic S
super-class Gnathostomata

subphylum Vertebrata

class Amphibia Linnaeus, 1758 -- Amphibians
class Aves -- Bird X
class Chondrichthyes -- cartilagineux Poisson
class Mammalia Linnaeus, 1758 -- Mammalian
class Reptilia Laurenti, 1768 -- Reptile S
super-class Agnatha

class Cephalaspidomorphi (Lamprey)
class Myxini (Myxine)
class Pteraspidomorphi (animal fossils)

super-class Osteichthyes -- Poisson with osseous skeleton

class Actinopterygii -- Poisson with radiated fins
class Sarcopterygii

External bonds

Beats-smg: Chuordinē Simple: Chordate Zh-min-nan: Chit-soh tōng-bu̍t

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