Earth history; Permian
The world map shows Pangaea, which is the name of the super-continent stretching from pole to pole. Long distances to the sea lead to a change in the climate and widespread deserts. A group of four-legged vertebrates, independent of periodical water dwelling, appeared. They had developed a new type of egg, which could be lain on dry land; with a hard shell and nourishment for the fetus both in the yolk and the egg white. The bones in the neck and foot made it possible for the animals to lift their heads and walk more efficiently. These animals could walk long distances into Pangaea; they were no longer amphibians, but reptiles. Towards the end of the period, large mammal-like reptiles spread across the continent. A fall in the sea-level lead to a reduction in the size of the shallow-sea environments, thus leading to the total extinction of all trilobites, tabulate corals and rugose corals. Large groups of bryozoans, brachiopods, sponges and crinoids, also vanished.
Publisert 30. jan. 2009 09:07 - Sist endret 18. mai. 2011 16:00