ICHTHYOSTEGALIAICHTHYOSTEGALIA
| Poland 1966 | Tonga territory Niuafou 1989 |
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| Ichthyostega Ichthyostega (Ichthyostegidae) (ICHTHYOSTEGALIA) |
Ichthyostega Ichthyostega (Ichthyostegidae) (ICHTHYOSTEGALIA) |
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| Acanthostega Acanthostega (Acanthostegidae) (ICHTHYOSTEGALIA) |
Acanthostega Acanthostega gunnari (Acanthostegidae) (ICHTHYOSTEGALIA) |
When a certain thing of fish went on the land, and air came to breathe, as for "the gills cover" which developed so that it was underwater, and gills breathed, this degenerated because they became unnecessary, and it took place, and cranial bones developed. However, although it entered the land, the amphibians did not completely leave the water, and the surface of the body did the skin of the form of always wet mucous membrane not to dry and the larva which it was deposited underwater without the egg being wrapped in a husk, and was hatched was underwater as a ladle and did "gills breathing", and air came to breathe when it grew up. It is shown in the ichthyostegalian which the model of such amphibians becomes it around the end of Devonian period, and appeared.
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