Pangea Rodinia and Gondwanaland: species and there origins on ancient continents

Pangea Rodinia and Gondwanaland: species and there origins on ancient continents

Siluruian and Devonian: 

Silurian Period
443.7 – 416 million years ago

Permian-Triassic

 Early Eocene 50-35 Ma

The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5Mya (million years ago), to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya (ICS2004,[5] chart). As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by several million years. The base of the Silurian is set at a major extinction event when 60% of marine species were wiped out. See Ordovician-Silurian extinction events.
Silurian Period
443.7 – 416 million years ago
SilurianGlobal.jpg
Mean atmospheric O2content over period durationca. 14 Vol %[1]
(70 % of modern level)
Mean atmospheric CO2content over period durationca. 4500 ppm[2]
(16 times pre-industrial level)
Mean surface temperature over period durationca. 17 °C[3]
(3 °C above modern level)
Sea level (above present day)Around 180m, with short-term negative excursions[4]



























Devonian Period
416 – 359.2 million years ago
LateDevonianGlobal.jpg
Mean atmosphericO2 content over period durationca. 15 Vol %[1]
(75 % of modern level)
Mean atmosphericCO2 content over period durationca. 2200 ppm[2]
(8 times pre-industrial level)
Mean surface temperature over period durationca. 20 °C[3]
(6 °C above modern level)
Sea level (above present day)Relatively steady around 180m, gradually falling to 120m through period[4]






















The Devonian is a geologic period and system of the Paleozoic Era spanning from 416 to 359.2 million years ago(ICS2004,[5] chart). It is named after DevonEngland, where rocks from this period were first studied.

During the Devonian Period the pectoral and pelvic fins of lobe-finned fish evolved into legs[6] as they started to walk onland as tetrapods around 397 Ma.[7] Various terrestrial arthropods also became well-established.

The first seed-bearing plants spread across dry land, forming huge forests. In the oceans, primitive sharks became more numerous than in the Silurian and the late Ordovician, and the first ray finned and lobe-finned bony fish evolved. The first ammonite mollusks appeared, and trilobites, the mollusc-like brachiopods, as well as great coral reefs were still common. The Late Devonian extinction severely affected marine life.

The paleogeography was dominated by the supercontinent of Gondwana to the south, the continent of Siberia to the north, and the early formation of the small supercontinent of Euramerica in between.

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