Paleozoic

The Paleozoic, Paleozoic or even Erdaltzeit, is the oldest of the three geological ages ( eras ) in the Phanerozoic eon that is shared within the geological time scale. It covers the period from about 541 million years to about 252.2 million years ago. In the Paleozoic, the Mesozoic followed ( Mesozoic ).

Classification of the Paleozoic

Position of the Paleozoic in the Phanerozoic:

• Eon: Phanerozoic ( 541-0 mya ) Era: Cenozoic ( Cenozoic ) ( 66-0 mya )
• Era: Mesozoic ( Mesozoic ) ( 252.2 to 66 mya )
• Era: Paleozoic ( Palaeozoic ) ( 541 to 252.2 mya )

The Paleozoic Era is divided into the following systems ( above the youngest, the oldest below ):

• Era: Paleozoic Era ( 541 to 252.2 mya ) System: Perm ( 298.9 to 252.2 mya )
• System: Carboniferous ( 358.9 to 298.9 mya )
• System: Devon ( 419.2 to 358.9 mya )
• System: Silurian ( 443.4 to 419.2 mya )
• System: Ordovician ( 485.4 to 443.4 mya )
• System: Cambrian ( 541 to 485.4 mya )

The periods Permian, Carboniferous and Devonian form the Late Paleozoic, during the Lower Paleozoic covers the periods Silurian, Ordovician and Cambrian.

Before the Cambrian is the so-called Precambrian; it includes the aeons from the formation of the earth about 4,600 mya to the beginning of the Paleozoic. These are the Proterozoic ( 2500-541 mya ), the Archean ( 4000-2500 mya ) and the Hadean. ( 4600-4000 mya ).

Life in the Paleozoic

The Paleozoic Era began with the appearance of small, hard-shelled fossils, small shelly fauna of the so-called, in the step of Tommotium at the base of the Cambrian. In the Cambrian, almost all developed still existing tribes of the animal kingdom.

Life was initially restricted to the oceans. First reef formers were already known from the Precambrian algae formations ( stromatolites ). But already during the Middle Ordovician were formed larger, more complex reefs. At the end of the Ordovician, there was the same time as the oberordovizischen icing to a mass extinction. From the Silurian a diverse marine reef community is known ( stromatoporoids, corals, bryozoans ). Remains first Silurian land plants ( Psilophyta ) have been handed down, the plants made ​​the leap to the country probably even earlier in the late Ordovician.

In Devon, the reef communities developed further. In Germany especially the Kalkmulden the Eifel and Sauerland are an example of this. From Upper Devonian strata show that life had already conquered the land: they are hands down the first amphibians that at least partially lived on land. In the Upper Devonian again was a great mass extinction, which many marine creatures fell victim.

In the Carboniferous and Permian, the continents were already inhabited by a diverse wildlife and overgrown by the forests, whose fossils found today in the Steinkohlenflözen. Especially arthropods could develop some gigantic proportions in the oxygen-rich atmosphere of the Carboniferous, such as insects such as the giant dragonfly Meganeura who lived in the warm, humid air of the marshes. The largest land-dwelling animals in the Permian were the therapsids, the " mammal-like reptiles ".

At the end of the Paleozoic, in the Upper Permian, the biggest mass extinction of Earth's history occurred. Died over a period of about ten million years between 75 and 90 percent of all then-existing species. The goniatites, forerunner of the later so successful in the Mesozoic ammonites, extremely scarce escaped extinction, only two or three species survived the crisis in Permian to Triassic in the following. The since the Cambrian widespread trilobites died out completely, and many other species did not survive this incision.

Geological findings suggest that a change of climate as a possible cause of change. The polar regions were covered in the Permian of continents on which formed large ice sheets. The geographical area of ​​distribution of many tropical, heat- loving species was restricted to the Tethys, a golf -like sea, which jutted from the east into the supercontinent Pangaea.