Therapsid
| Therapsid | ||||||||||||||||||
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 Reconstruction imagination figure of the cynognathus | ||||||||||||||||||
| The geological age | ||||||||||||||||||
| Permian late - present age | ||||||||||||||||||
| Classification | ||||||||||||||||||
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| Scientific name | ||||||||||||||||||
| Therapsida Broom, 1903 | ||||||||||||||||||
| Suborder, declining trend | ||||||||||||||||||
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Therapsid (じゅうきゅうるい, Therapsid or beast bow eyes, Therapsida) is one of the taxa of dolosse, a single bow. It was the figure such as the lizard which there was no great difference between and Panlong kind in the early days, but, in the group which evolved from Panlong kind, acquired hair and constant temperature characteristics in the latter period. The mammals are only actual money group.
Table of contents
History of evolution
I am said to be it when I evolved from the group near the Panlong kind スフェナコドン department in the Permian first half year in the Paleozoic era in the origin of the therapsid. The collaborating evidence includes anatomical features such as the skull or the backbone. The oldest therapsid which could be known was a creature called テトラケラトプス where I inhabited from 268,800,000 years to 259,700,000 years ago now.
BiAl mosques appeared successively as an immediate early group followed by the main group such as ディノケファルス, Heterodonta, beast teeth appeared, too. When Panlong kind begins to walk a way of the decline by some kind of causes before long, the therapsid develops in form taking advantage of this. The therapsid from Permian middle to the latter period monopolized a lot of niches in the land ecosystem and expelled Panlong that declined.
Although I include a carnivorous group early, ディノケファルス is almost the grazing animal which is slow-witted with large size including モスコプス. The characteristic includes a lot a group having characteristics such as a huge tusk or a corner, the skull which thickened strangely so that I am expressed in the name of ディノケファルス (will of the terrible brain). The notable thing is that the only trace like some kind of glands was discovered in fossilized skin of エステメノスクス in this group. This is said to be a sweat gland, but the details are unclear. This group became extinct without waiting for a Permian end.
The group representing Heterodonta is D keno Don. The cosmetic characteristic of this group is a huge tusk of two of them which stuck out from the way of speaking part (origin of the name of the D keno Don). I leave a buccal tooth with the primitive kind, but the tooth except the cuspid disappears with the kind that evolved and is replaced by a bill and the pad of the keratin. D keno Don employs you late in Permian Period, and it may be said that it is the most successful group in therapsid.
The group called beast teeth was defined in 1860 by Richard Orr wen. A dental formula (there is the group which fitted eating plant secondarily) indicating the adaptation to eating meat, a finger type of forefoot are 2-3-3-3-3, and the characteristic becomes. Main groups include ゴルゴノプス, テロケファルス, keno Don. As for ゴルゴノプス which was the strongest predator, there were a lot of small hollows in the rostrum part of the fossil at the time of one. This is said to be a trace of the sinus hair. Therefore the possibility that this group has already got to hair is pointed out. Then, bone-related secondary palate develops in テロケファルス which appeared, and parietal foramen reduces, and it is thought that I was getting constant temperature characteristics.
It was therapsid in accord with the top of the prosperity, but, in the case of mass extinction of (P-T border), most kinds except the small portion including keno Don, テロケファルス became extinct on a day at a Permian end, and the prosperity was finished in this way.
When I put it early in a Triassic period for the Mesozoic, it be said that it is never 程, and keno Don prospers again on a day. Representative things of this time include Lystrosaurus, and this becomes the index fossil. I am discovered in South Africa and India, China, Europe, the South Pole and am considered to be one of the evidence that there was Pangaea continent. In addition, the bow rear kind that テロケファルス fitted plant food as a derivation class highly appears.
And it is the keno Don which is said to be it when similarly it was derived from テロケファルス to have lengthened a power in earnest after a Triassic period begins. It was not existence to be overwhelmed elsewhere in the Permian Period, and to be outstanding, but I go into an ecosystemic blank just after the mass extinction, and a convincing predator including the cynognathus appears. Although completion of the secondary palate and the acquisition of two dentition characteristics, the modification of the temporomandibular joint are extremely incomplete in the group which neared Mammalia, I acquire the mammals-like characteristic including the shift to the standing straight walk system. The oldest mammals (lactation form?) Oh, I inhabited 225 million years ago. However, in last part of Triassic period, moderate mass extinction attacks the earth again, and D keno Don becomes extinct virtually. The keno Don became extinct except very few systems. In addition, テロケファルス and the bow rear kind are thought to have disappeared in the middle of Triassic period.
The some exceptions are you keno Don. It is the system which appeared late in a Triassic period including avian tele Don, tritylodont, lactation form. Avian tele Don was in the first half of the Jurassic, and the tritylodont department survived until earlier period of Cretaceous. Lactation form is taxa including the mammalian and closely related system. The mammals become the therapsid existing alone.
After the Jurassic, the therapsid was robbed of its niche of the large animal by the large reptiles including the dinosaur and remained small. But, in the Mesozoic, it is thought that the mammals greatly exceeded a dinosaur in number.
When I arrive after it, I refer to a mammalian clause.
System
Subdivision
About the classification of the therapsid, all researchers do not agree. The following is only example.
- †テトラケラトプス department Tetraceratopsidae
- †BiAl mosques suborder Biarmosuchia
- BiAl mosques department Biarmosuchidae: BiAl mosques
- フチノスクス department Phthinosuchidae
- エオティタノスクス department Eotitanosuchidae: エオティタノスクス
- Eutherapsida
- †ディノケファルス suborder Dinocephalia: エステメノスクス、Anteosaur、モスコプス
- Neotherapsida
- †異歯亜目 Anomodontia
- Beast teeth Theriodontia
- †ゴルゴノプス suborder Gorgonopsia: ゴルゴノプス、イノストランケビア、リカエノプス
- Genuine beast teeth Eutheriodontia
- †テロケファルス suborder Therocephalia: リコスクス, you beautifulness bell dia
- Bow rear superfamily Baurioidea: The bow rear
- Keno Don suborder Cynodontia: プロキノスクス、トリナクソドン、Cynognathus、オリゴキフス
- †テロケファルス suborder Therocephalia: リコスクス, you beautifulness bell dia
References
- Ryuichi Kaneko "lactation type reptiles is ISBN 4-02-259709-7 in unknown ancestor Asahi Shimbun 〈 morning sun selected books 〉, 1998 of the Homo sapiens".
- J, C McLaughlin product, image "the dragon which disappeared is new thought Ikuo Obata, Hiromichi Hirano reason Iwanami Shoten, 1982 about the ancestors of mammals".
- For Yukimitsu Tomita sentence, Ito third class male, Yasuko Okamoto illustration "extinction mammals illustrated book" Maruzen, 2,002 years, it is ISBN 4-621-04943-7.
This article is taken from the Japanese Wikipedia Therapsid
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